MRC Cognition and Brain Sciences Unit

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ATTENTION GROUP PROGRESS REPORT

Overview

The attention programme addresses the twin problems of selective perception and cognitive control. Together, these have become central issues in modern cognitive neuroscience (Desimone & Duncan, 1995; Miller & Cohen, 2000), with rapid progress deriving from well-defined behavioural questions and a basis in known sensorimotor physiology.

Together, our Projects address problems of visual, auditory and tactile attention, spatial cognition, consciousness, executive function and intelligence.

Project A1 focuses on visual selective attention. In a series of papers published in the previous funding period and interregnum (Desimone & Duncan, 1995; Duncan, Humphreys & Ward, 1997) we introduced a neurophysiological model of attentional functions. This integrated competition model was based on a series of behavioural, neuropsychological and neurophysiological studies, including four Nature papers over this period (Chelazzi, Miller, Duncan, & Desimone, 1993; Duncan, Ward, & Shapiro, 1994; Duncan, Martens, & Ward, 1997; Humphreys, Romani, Olson, Riddoch, & Duncan, 1994). Work based on this model is now a focus in many major laboratories (e.g. Kastner, De Weerd, Desimone, & Ungerleider, 1998; O'Craven, Downing, & Kanwisher, 1999; Rees, Frackowiak, & Frith, 1997). In our own work, we have addressed the contributions of prestriate, inferotemporal and prefrontal cortex to attentional function (Everling, Tinsley, Gaffan, & Duncan, 2002, Nature Neuroscience). In neuropsychological work, we have related components of our physiological model to deficits in a well-specified formal model of attentional function (Bundesen, 1990; see Duncan et al., 1999, Journal of Experimental Psychology: General). In new behavioural studies, we have addressed separation and integration of visual attention, auditory attention and response selection. Preliminary experiments using functional neuroimaging have also appeared.

Project A2 focuses on spatial representation, spatial impairment, and the development of mutually beneficial links between theoretical advance and clinical application. The work on impairment has three main themes. The first lies in the relationship between persistent pathological spatial bias and supervisory processes engaged in the maintenance of alert, goal-directed states (e.g., Robertson, Mattingley, Rorden, & Driver, 1998b). In addition to informing experimental development and effective clinical intervention with adults, this work has led to the prediction, demonstration, and remediation of spatial bias in children with executive deficits of developmental origin (e.g., Manly, Robertson, & Verity, 1997). The second theme concerns interactions between motor planning/initiation and spatial awareness in brain damaged adults and in children (e.g. Dobler et al., 2001a). A final theme in impairment concerns experimental analysis of cross-modal competition/enhancement of spatial representations (e.g., Mattingley, Driver, Beschin, & Robertson, 1997) and the effects of right parietal damage on non-visual representation (e.g. Farrell & Robertson, 2000). One strong aspiration has been to make the results of the work relevant and accessible to clinical audiences. Accordingly, publications in clinically directed journals and book chapters have accompanied more theoretical dissemination, including in Nature and Psychological Bulletin. Work on normal intact people has demonstrated the effect of perceptual contact with a structured environment on frame of reference and self-location (Marcel & Dobel, in press) and has led to discovery of individual differences in tactile fusion and allochiria that may underlie differential manifestations of spatial neglect with brain damage (Project A2.5).

Project A3 investigates the selective perception of sounds ("Auditory Scene Analysis") by healthy individuals, stroke patients, and deaf people fitted with a cochlear implant. It combines behavioural experiments with the capacity to perform EEG and functional imaging experiments at the CBU and elsewhere in Cambridge. We have shown that the build-up of auditory streaming is critically dependent on attention in healthy individuals, and that streaming is reduced in the contralesional ear of stroke patients, diagnosed with unilateral neglect on the basis of performance on visual tasks (Carlyon, Cusack, Foxton, & Robertson, 2001, Journal of Experimental Psychology: Human Perception and Performance). Taken together, these two findings provide the first evidence that cortical processes are involved in auditory streaming (as opposed to the consequences of streaming simply being measurable in cortex). Further constraints on the neural basis for auditory scene analysis were imposed by an EEG study of the continuity illusion, performed in collaboration with Pulvermüller and colleagues (Micheyl et al., in press, Journal of Cognitive Neuroscience). The study, which used the mismatch negativity technique, demonstrated the first neurophysiological correlate of an auditory illusion in human listeners. We have also applied our knowledge of auditory scene analysis to an important clinical population. Many cochlear implant users can understand speech in quiet, but even the most successful experience difficulty in segregating competing sounds. This research benefits from strong clinical collaborations with Addenbrooke's hospital, Cambridge, and with research groups worldwide. Together with colleagues in Melbourne, Australia, we have developed sophisticated hardware and software allowing us to apply arbitrary patterns of electrical stimulation to the auditory nerve. This has allowed us to identify some of the cues that implantees can and cannot use to separate two competing sounds, and to develop a model of how listeners perceive a mixture of sounds applied to one channel of their implant (Carlyon, van Wieringen, Long, Deeks, & Wouters, 2002, Journal of the Acoustical Society of America; McKay & Carlyon, 1999, Journal of the Acoustical Society of America).

Project A4 deals with consciousness, attention and bodily experience. In a variety of studies over the last two funding periods we have made several conceptual contributions to the study of consciousness and attention. One of these has been fractionation of consciousness (a) into first- and second-order consciousness corresponding to phenomenal experience and awareness, and (b) into split and disunified consciousness at each level (Marcel, 1993, 1994, 1998; Marcel, Tegnèr & Nimmo-Smith, in press). This has led to a new analysis of anosognosia for plegia following stroke (Marcel et al., in press). A forthcoming issue of the Journal of Consciousness Studies (Eds Jack & Roepstorf) will be devoted to issues raised by this. We have also extended the topic to cover bodily experience, action and emotion (Marcel, 2000, Marcel, in press-b; Lambie & Marcel, 2002). Indeed our theoretical paper on emotion experience in Psychological Review (Lambie & Marcel, 2002) integrating emotion, cognition and neuropsychology, although only recent, has had a major impact on different areas of psychology and on philosophers, leading to invited presentations at the International Society for Emotion Research (July, 2002) and at the American Psychological Association (2003). Introduction of the role of two neglected aspects of attention (self vs world focus; immersion vs detachment) has informed and led to work on touch and awareness of action (Gallagher & Marcel, 1999; Marcel, in press-b; Marcel et al., in press).

In Project A5 we turn to cognitive control, and in particular the functions of prefrontal cortex. Until recently, it was widely accepted that the lateral frontal cortex was organised according to information content, dorsolateral and ventrolateral prefrontal cortex being specialized for respectively spatial and object working memory (e.g. Goldman-Rakic, 1994). Previous and continuing work by Owen (Owen, Evans, Petrides, 1996a; Owen, Doyon, Petrides, Evans, 1996b) has largely overturned this view; as now widely accepted, complexity of processing rather than information content is the key consideration in prefrontal specialization. Our new work has dealt more fully with the functions of ventrolateral prefrontal cortex, addressing links between its role in memory processes and its role in attention. Functions of orbitofrontal cortex have been explored with further emphasis on integration with lateral frontal regions. Addressing hemispheric asymmetry, we have questioned the conventional view that left and right prefrontal cortex are strongly specialized for (respectively) memory encoding and retrieval. Building on all these results, we have recently put forward a new general view of prefrontal function (Duncan, 2001a, Nature Reviews Neuroscience; see also Duncan & Owen, 2000a). Rather than strict regional specialization, this model proposes substantial flexibility in the function of prefrontal neurons. Such flexibility may help account for our neuroimaging results, recently reported in Science, suggesting a key role for prefrontal cortex in general intelligence (Duncan et al., 2000). Finally, functional neuroimaging, psychopharmacological and neuropsychological studies in Parkinson's disease have been combined to investigate functional interactions between discrete nuclei of the basal ganglia and their corresponding targets within the frontal lobe. These studies have important theoretical and clinical implications and, with over 15 publications, represent one of the most extensive bodies of work in this area worldwide (for review see Owen, 1997).

Project A6, as with A2, is based on the synthesis of theoretically driven and clinically applied work, here in the context of non-spatially-specific attentional and executive disorders. The close links with Evans and colleagues at the Oliver Zangwill Centre for Neuropsychological Rehabilitation have been important in binding clinically relevant studies with more exploratory projects including functional neuroimaging (Manly et al., submitted-b), electrophysiology (Datta et al., submitted) and studies with healthy volunteers (e.g., Manly, Lewis, Robertson, Watson, & Datta, 2001b). To date, few systematic attempts have been made in the rehabilitation of such disorders and, as the key capacities that usually facilitate change are compromised, it is an inherently challenging task. Preliminary results using environmental cues to trigger executive reviews have been positive (e.g., Manly, Hawkins, Evans, & Robertson, 2001a). Elements of A6 have also informed the development of assessment tools for children, including the Test of Everyday Attention for Children (Manly et al., 2002a), itself the subject of a recent symposium of the International Neuropsychological Society. In clinically pioneering work with patients diagnosed as persistent vegetative state (Menon et al., 1998; Owen et al., in press), Owen has worked with the team at the Wolfson Brain Imaging Centre to demonstrate the potential of functional neuroimaging in the diagnosis and management of this difficult condition. This work has attracted considerable attention from scientists and clinicians internationally, as well as from the world's press.

This work is firmly in line with the core CBU remit of integrating cognitive and brain systems theory. Our methods include cognitive studies in normal and clinical groups, functional neuroimaging, event-related potentials, and psychopharmacology. The work is also in line with the goal of two-way interaction between basic science and clinical application, with both assessment of clinical methods based on theoretical work, and new theoretical questions deriving directly from clinical practice. Much of this clinically-oriented work (Projects A2, A6) was initially proposed by Dr I. Robertson; following his departure in 1999, these projects (along with the new proposals in Project A3) have been under the scientific direction of Dr T. Manly.

The programme is closely dependent on links to other Cambridge groups. The bulk of our functional imaging programme, both in normal subjects and clinical groups, depends on the collaborative input and facilities of the Wolfson Brain Imaging Centre (in particular, Professors J. Pickard and E. Bullmore). In maintaining and using the Cambridge Cognitive Neuroscience Research Panel, we depend on regular research meetings with Dr N. Antoun of the Addenbrooke's Department of Radiology, with additional input from the Addenbrooke's MRIS Unit. Clinical aspects of our programme, including work in rehabilitation and cochlear implants, depend on strong relationships with Neurology (Professor J. Hodges), Neurosurgery (Professor J. Pickard), Stroke Medicine (Professor J-C. Baron, Dr E. Warburton), Rehabilitation (Dr S. Kirker) and Audiology (Mr D. Baguley, Mr. P. Axon, Ms. Z. Vanat) at Addenbrooke's Hospital, with the Oliver Zangwill Centre for Neuropsychological Rehabilitation (Dr J. Evans), and with the Department of Developmental Psychiatry (Professor I. Goodyer). Our work on Parkinson's Disease is a collaboration with the MRC Centre for Brain Repair (Drs. R. Barker, S. Lewis). Other collaborations include the University Departments of Experimental Psychology (Professors T. Robbins, B. Moore), Psychiatry (Professor T. Holland, Dr B. Sahakian), Anaesthesia (Professor D. Menon), and Anatomy (Drs. J. Parkinson, A. Roberts).

Project A1: Visual attention and integrated competition.

The problem of visual attention is defined by two key concepts. One is limited capacity, measured by performance decrements when a person must identify two or more things at once. Subjectively, devoting attention to one thing implies withdrawing it from others. The second is selectivity. Limited capacity requires a choice of which aspects of the input to process.

In this project, attention is conceived as a problem of biased and integrated competition in the network of cortical and subcortical brain systems that respond to visual input. These include multiple "visual areas" in occipitotemporal and occipitoparietal cortex, along with associated subcortical structures including the superior colliculus and pulvinar. Visual responses are also seen in many areas of the frontal lobe, including the frontal eye fields, premotor cortex and prefrontal cortex. The integrated competion model is based on three general principles:

(i) In many or all visually-responsive brain systems, objects in the visual input compete to be processed. Strengthened representation for one object is bought at the expense of weakened representation for others. It is this competition that gives vision its aspect of limited capacity.

(ii) In any task context, competition is biased by priming or pre-activation of cells coding currently relevant objects. Priming lends relevant objects in the visual field a competitive advantage, giving vision its aspect of top-down selectivity.

(iii) In behaviour, we interact with whole objects, whose different properties (shape, motion, egocentric location etc) and implications for action will in part be represented in different parts of the sensorimotor network. Many behavioural studies show that, to a large extent at least, objects are the "units" of attentional selection: Attending to an object makes its different properties concurrently available for report and control of action. Accordingly, competition must be integrated such that, across the sensorimotor network, the same selected objects assume dominance. In Project A3, related issues concern attention and auditory scene analysis.

In the previous funding period, the integrated competition model was developed from a broad range of behavioural, and neuropsychological results (Desimone & Duncan, 1995; Duncan, 1996; Duncan et al., 1997; Duncan, 1998; Humphreys, Duncan, & Ward, 1999). In this quinquennium, the model has been the guide for research across these levels.

A1.2 Human neuropsychology
Scientific direction: Duncan (15%)
Grant-supported posts and visitors: Rorden, Ludwig, Bonfiglioli, van Raamsdonk Students: Peers

According to the integrated competition model, objects in the visual field compete for processing over an extended period, as directly suggested by physiological data. This links the model naturally to behavioural models based on weighted parallel processing. In a collaboration with Dr C. Bundesen from Copenhagen University, we have developed one such model - Bundesen's Theory of Visual Attention (TVA) - for quantitative analysis of attentional deficits after brain damage. Correspondences can be shown between parameters of attentional function in this model and components of the integrated competition scheme (Duncan, 2001b).

In TVA (Bundesen, 1990), objects in the visual input are concurrently processed for entry into a visual short-term memory (VSTM), from which they can be reported. For many displays, total processing rate is fixed; competition or attentional weighting determines how rapidly each separate display object is processed and hence races for VSTM access. In Bundesen's work, the model has been fit quantitatively to data from a broad range of tasks and attentional manipulations. For patient work, the most useful task is partial report (Duncan, 2001b). Brief visual displays contain mixtures of targets (to be reported) and nontargets (to be ignored). For example, participants might attempt to name just the white letters in a mixed display of white and black. By presenting targets in one or both visual fields, we can measure attentional weighting (strength of competition) for contralesional and ipsilesional sides. Clinical "extinction" (see Project A2), for example, would reflect low competitive strength on the contralesional side, and hence poor contralesional performance when there is concurrent ipsilesional material. At the same time we measure several nonspatial aspects of visual function: total processing rate across the visual field (rate of performance improvement with increasing exposure duration); capacity (number of objects) of VSTM; and top-down control or relative attentional weighting of targets and nontargets.

Our first studies, run in Birmingham with the group of Dr G. Humphreys, concerned lesions of the right inferior parietal cortex (Duncan et al., 1999). As expected in such patients, there were variable degrees of unilateral neglect assessed by standard clinical tests. Following standard accounts of neglect, the TVA analysis indeed showed a consistent attentional bias (reduced attentional weight) against the left (contralesional) field. Even more closely related to clinical neglect, however, was a bilateral reduction in total processing rate, unrelated to lateral bias. Strikingly, top-down control was entirely preserved, in both halves of the visual field. In Project A2, nonspatial aspects of neglect are also described for the auditory domain.

In a second study (Duncan et al., submitted) we used similar methods to analyze dorsal and ventral variants of classical "simultanagnosia". In simultanagnosia, the most conspicuous deficit is inability to process multiple objects in a visual display. For both variants, however, our data suggest that this is not the primary impairment. Instead, bilateral parietal lesions (dorsal variant) or left occipitotemporal lesions (ventral variant) produce a massive reduction in simple rate of uptake of visual input. Though deficits can be especially obvious with multiple-object displays, even single-object displays are equally affected with comparable measurement methods.
With the development of the Cambridge Cognitive Neuroscience Research Panel, we have gone on to analyze similar attentional parameters in a range of patient groups. Normalization of patient MRIs, using the methods of Brett, Leff, Rorden, & Ashburner (2001) (see Progress Report, Project MR3.3), allows consistent lesion description in standard brain atlas coordinates (Figure A1.2). While this work is still in progress, already it shows several unexpected results. For focal, unilateral parietal lesions, the expected spatial bias is clearly accompanied by nonspatial deficits in processing rate and VSTM capacity. These deficits are bilateral, and not associated with lesion spread into the occipital cortex. They are also seen after lesions of either hemisphere, and affect identification of both letters and faces. Evidently, parietal cortex is involved not just in spatial distribution of attention, but in the basic process of creating a conscious, reportable percept of any object in any part of the visual field. Though the results are preliminary, they also begin to suggest an intriguing dissociation between spatial and nonspatial deficits. While lateral attentional bias can follow either superior or inferior parietal lesions, and is largely predicted by lesion volume, nonspatial deficits are specifically associated with lesions of the inferior parietal lobule.

Figure A1.2. Slices from individual patient's MRI (top), transformed to standard space and re-sliced to match corresponding slices (bottom) from atlas of Talairach & Tournoux (1988). Lesion tracing in red. For comparison with this patient's lesion, yellow triangles show activation peaks from a PET study of lateral attentional bias in normal subjects.

In collaboration with Professor J. Driver (London), we have also studied patients with unilateral lesions of left or right prefrontal cortex. Once more, the spatial distribution of attention is abnormal, with some patients showing lateral bias like that of parietal patients. In line with the integrated competition view, the data suggest that any cortical lesion - occipitotemporal, parietal or frontal - can produce a global competitive imbalance against the affected side. Intriguingly, frontal and parietal lesions are also similar in their failure to affect top-down control (differential weighting of targets and nontargets). To date, indeed, we have been unable to find control deficits in any patient group, in tasks requiring spatial or nonspatial selection, and with fixed or varying target definition across trials. In terms of the integrated competition model, these results raise the question of how top-down priming signals are distributed and controlled.

A1.3 Behavioural studies
Scientific direction: Duncan (20%)
Grant-supported posts and visitors: Arnell, Bonfiglioli

In behavioural studies, temporally extended competition between visual inputs is most clearly shown by direct manipulation of temporal separation. For successive visual targets, interference extends over separations up to a half second or more, an order of magnitude greater that the predictions of conventional serial models. In the previous funding period, such measurements of "attentional dwell time" were used to address a number of issues, including competition within and between objects (Duncan et al., 1994) and within and between sensory modalities (Duncan et al., 1997). In the current period, a number of projects have used related methods to address the broader architecture of attentional competition.

In visual dwell time studies, interference is measured between visual targets presented in rapid succession. A related phenomenon, well studied in the behavioural literature, is the "psychological refractory period" (PRP); if speeded responses must be made to two successive stimuli, the second will often be delayed while the first is chosen and executed (e.g. Pashler, 1989). In classical accounts, visual competition and PRP are ascribed to quite different causes, the latter reflecting queuing in a serial response selection bottleneck (Pashler, 1989), but overlapping sources of processing limitation in these two cases have also been proposed (Jolicoeur, 1998). The debate reflects a broader issue in the study of dual task interference - the relative importance of local or domain-specific processing conflicts vs. more global attentional limitations.

To resolve the issue we have developed a new dual task method based on randomized mixing of event types within each trial (Arnell & Duncan, 2002). Auditory stimuli (e.g. simple tones) require speeded keypress responses (cf. PRP experiments), while visual stimuli (e.g. masked digits) require unspeeded identification. Randomization means that, on each trial, the two successive events can either be both auditory (conventional PRP), both visual (conventional measurement of visual dwell time), or one of each (hybrid). Certainly, such experiments can show strong double dissociations, with striking interference in both conventional cases and reduced interference in hybrids. Such results support classical models, confirming the importance of domain-specific processing conflicts. At the same time, even modest increases in task complexity can bring substantial interference even to hybrid cases. Apparently, some sources of processing conflict are so general as to cause great difficulty, for example, in identifying a visual digit while engaged in a complex, auditory stimulus-response translation. For physiological models of visual attention these results raise important questions. Though much competition may occur in classical visual areas, what is the neural basis for further, more global sources of processing conflict?
A key proposal of the competition model is integration of competitive dominance between visual areas coding different aspects of a selected object. Two further projects have extended our study of integration into new domains. In vision, input is organized in time as well as space, creating segmentation not only into objects but into discrete events. As seen for objects, we have demonstrated attentional integration within events: if a pause in a visual sequence is perceived as defining onset of a new event, it triggers a new attentional demand, while if it is perceived as a hesitation in an existing event, no new demand results (Sheppard, Duncan, Shapiro, & Hillstrom, 2002). A further question concerns spatial integration between vision and action. Our work here was inspired by the group's prior clinical work in unilateral neglect (see Project A2), showing that unseen movements of the left hand in left space can increase visual performance in the neglected left field. In a series of experiments (Bonfiglioli, Duncan, Rorden, & Kennett, 2002), we searched for similar integration in normal participants. In response to a tone, an unseen reach was planned and executed to one or the other side of space. At varying temporal intervals, visual events occurred close to left and right reach targets. At no interval, and under no reach conditions, did we observe a shift of visual attention towards the position of the reach target. This contrasts not only with the neuropsychological phenomenon but with positive results for related manipulations in young children (see Project A2). The results suggest that independence of lateral biases in vision and action may be a specific achievement of the healthy adult brain. Such independence may not be fully developed in childhood, and may potentially be compromised by brain insult.

A1.4 Functional neuroimaging
Scientific direction: Duncan (10%)
Other MRC posts: Epstein (2 years, 30%); Wojciulik (1 year, 100%)

Major themes in the functional imaging work of Duncan and Epstein are described elsewhere (frontal lobe function, Project A5; scene representation, Project A2). Here we describe preliminary experiments concerning visual attention and awareness.

In the neuropsychology of visual attention, it is generally assumed that parietal cortex has some specific and central role in attentional control (e.g. Corbetta & Shulman, 2002). In a PET study (Vandenberghe et al., 2000), we tested its role in switching from one attended location to another. Certainly we found bilateral parietal recruitment (intraparietal sulcus or IPS) when participants direct attention to a specific object in left or right hemifield. Activity was insensitive, however, to the frequency of attentional switches. A second possible control function is filtering out of visual distractors. In an fMRI study, we found bilateral IPS recruitment when an attended target letter was accompanied by irrelevant distractors; on the left, however, a similar recruitment was produced by a simple decrease in stimulus contrast. More broadly, IPS recruitment is seen with a wide range of processing demands, in domains from visual discrimination to working memory, manual or verbal response selection and problem solving (Cabeza & Nyberg, 2000). As we have documented for regions of prefrontal cortex (see Project A5), such results suggest that regional specializations within the IPS are at best relative, with no area exclusively dedicated to specific visual control functions.

One recent proposal in the literature has been that frontoparietal systems play a central role in visual awareness (e.g. Dehaene et al., 2001). In several experiments, it has been reported that attended or conscious stimuli produce strong frontoparietal responses, while unattended or unconscious stimuli do not. As participants make decisions about the stimuli they see, however, it is unclear whether this frontoparietal activity reflects awareness per se or the resultant task control operations. In a preliminary fMRI study, we asked participants simply to attend to or watch one stream of objects while ignoring another. While no immediate task was required, a surprise test of recognition memory at the end of the experiment confirmed that the instruction was obeyed. In large regions of occipitotemporal cortex, perhaps extending forward to the hippocampus, responses were stronger to attended objects. Region-of-interest analyses of frontal and parietal cortex, however, showed absolutely no response to either attended or unattended events. Though further experiments are required, these first results suggest frontoparietal involvement not in visual awareness itself, but in visual control of behaviour.

In a related theoretical project, Epstein has linked recent cognitive neuroscientific results to the phenomenological description of the stream of thought proffered by William James in the Principles of Psychology. James argued that the stream of thought consisted of relatively stable moments (substantive thoughts) connected by phases of transition (transitive "thoughts"). Epstein (2000a, 2000b) argues that the substantive thoughts -- many of which have an imagistic content -- may reflect momentarily stable patterns of neural firing in perceptual processing regions of the brain such as the ventral visual stream. In contrast, the transitions between thoughts may be mediated by two mechanisms: a medial temporal lobe memory mechanism that supports a network of possible associations, and a frontal control mechanism that ensures that the direction of thought remains consistent with current behavioral goals. James' scheme is particularly interesting when considered in the light of the above neuroimaging studies linking activity in occipitotemporal and frontal-parietal regions to visual awareness and task control.

Project A2: Spatial representation and impairment.

This project has considered normal and pathological representation of space and the body. This includes between-modality and sensorimotor integration, spatial frames of reference, imagery, and the influence of attention on perception and action. A primary clinical focus has been on unilateral spatial neglect, a disorder that is associated with slowed recovery, poor response to rehabilitation and impoverished outcomes. In parallel with theoretical development, understanding the factors that may lead to chronicity and the investigation of ameliorative techniques have been central to these studies.

A2.1 Interactions of vision and action
Scientific direction: Robertson (2 years, 20%), Manly (10%)
Grant-supported scientists and visitors: Mattingley
Students: Dobler

In prior work, Robertson had shown how left-sided visual neglect in stroke is strongly affected by action programming and context. An example is the demonstration that left visual neglect can be alleviated by concurrent activity of the left hand - specifically if the movements occur within left space defined relative to the midline. This modulation of spatial attention appears to occur whether or not the hand can be seen by the patient and whether or not the activity is directed towards the current spatial task. In the current funding period, we have shown the positive clinical effects of encouraging patients to make such movements during everyday activities (Robertson, Hogg, & McMillan, 1998a; Wilson, Manly, Coyle, & Robertson, 2000). Modulation also occurs within the much tighter time-frame of computerised extinction measures (Mattingley, Robertson, & Driver, 1998). Replication and extension of these findings is now also taking place internationally (e.g. Frassinetti, Rossi, & Ladavas, 2001; Brown, Walker, Gray, & Findlay, 1999; Gainotti, Perri, & Cappa, 2002; Samuel et al., 2000). Dissemination of these and other therapeutic findings with neglect to the clinical as well as to the scientific community has been a strong aspect of this work (Manly, 2001; Manly, 2002; Manly, in press; Manly & Mattingley, in press; Manly & Robertson, in press; Manly, Ward, & Robertson, 2002b; Robertson, 1998a; Robertson, 1998b; Robertson, 1999a; Robertson, 1999b; Robertson, 1999c; Robertson, 2000; Robertson, 2001; Robertson, in press; Robertson & Halligan, 1999; Robertson & Hawkins, 1999; Robertson & Manly, 1999)

Although the clinical results are clearly suggestive of a high level interaction between movement planning/execution and the allocation of visual attention - as envisaged in the integrated competition model (see Project A1) - the precise mechanisms underpinning these effects remain unclear. One puzzling aspect is that intensive investigation with healthy adults has shown no hint of such a relationship (Bonfiglioli et al., 2002). Our recent work has, however, illustrated reliable effects of concurrent limb activity on visual attention in healthy young children (below the age of 9) - even on purely perceptual tasks (Dobler et al., 2001a). This is consistent with a process linking spatial attention and movement in development that becomes masked in maturity but which may be uncovered by acquired brain damage in adulthood. Further investigations are currently underway with children - in parallel with adults showing neglect - to further delineate this relationship. The findings also raises potentially important questions about reciprocal effects of impairment in movement or attention in development (see below).

A2.2 Spatial bias and non-spatial control functions
Scientific direction: Robertson (2 years, 20%), Manly (20%)
Grant-supported scientists and visitors: Rorden, Mattingley
Students: Dobler

Although unilateral neglect is observed with almost equal frequency immediately following left- and right-hemisphere stroke, there is a striking asymmetry in patterns of recovery with almost all chronic patients having right hemisphere damage and neglecting left space. Accordingly, it has been proposed that concurrent damage to other right hemisphere dominant systems might form the setting conditions that allow the spatial bias to persist (see A3 Proposal for more detailed account). In line with this view, we have shown that co-occurring deficits in non-spatial sustained attention (a capacity predominantly linked with the right hemisphere in neuropsychological and functional imaging studies) are indeed associated with persistent forms of the disorder (Robertson et al., 1997b). More compellingly, we have shown a direct modulatory effect of external alerting on spatial awareness among right hemisphere neglect patients (Robertson et al., 1998b). Continuing the theme of more general control functions, work with Dr N. Lavie (London) has demonstrated that awareness of information within the neglected field (in this case, distracting information) could be reduced by increasing the attentional demands of a task completed at fixation (Lavie & Robertson, 2001). Finally, we have shown a heightened tendency for patients to become caught-up in perseverative responses to ipsilesional stimuli, and further shown these to be strongly determined by the presence of response relevant but neglected contralesional information (Manly, Woldt, Watson, & Warburton, 2002c).

We have developed an argument that this relationship between spatial bias and non-spatial attentional limitations may also apply to children. In 1997, we reported on the case of a 10-year old boy who, despite above-average intellectual abilities and the absence of any clear etiological event or brain abnormality, showed a striking and persistent tendency to neglect information in left space (Manly et al., 1997). Our investigations of his non-spatial attentional function - which led to our development of the Test of Everyday Attention for Children (TEA-Ch), now a widely used clinical measure (Manly et al., 2002a) - revealed significant deficits in sustained attention. Subsequent investigations screening children for poor non-spatial sustained attention have confirmed this association within the normal school age population and in children diagnosed with attention deficit hyperactivity disorder (Dobler, Manly, Anker, Robertson, & Atkinson, submitted-a). Again, the parallels between these interactions in development and in the injured adult brain offer the prospect of a more complete life-span theoretical treatment. Current investigation concerns clinical implications of these results, including potential amelioration of spatial biases in children (which our research suggests may be relatively common), and interactions with motor and attentional functions.

A2.3 Non-visual spatial representation and cross-modal interaction.
Scientific direction: Robertson (20%, 2 years)
Grant-supported scientists and visitors: Mattingley, Rorden, Farrell

Detailed single case experimental designs have demonstrated the integration of spatial attention across sensory modalities and helped illuminate attentional effects in apparently primary sensory impairment. In the context of impaired left-sided sensation following right hemisphere lesion, for example, we have shown facilitation of tactile awareness when a visual cue is simultaneously presented at a proximal location (Rorden, Heutink, Greenfield, & Robertson, 1999). In contrast, when tactile and visual stimuli are simultaneously presented within ipsi- and contralateral space, a competitive cross-modal extinction effect is observed (Mattingley et al., 1997).
A further important aspect of parietal function lies in updating of the body's location in external space. In an initial study, participants were rotated with vision occluded, and then asked to point towards previously seen objects within a fixed spatial array. When updating their position in line with the experienced rotation, neurologically healthy volunteers show no effect of the extent of rotation in their response times. If however, they are asked to point to the objects as if no rotation had occurred, the proportionate relationship between reaction time and degree of rotation suggests mental rotation back to the starting position (Farrell & Robertson, 1998). In contrast, patients with right posterior damage showed no evidence of such automatic updating (Farrell & Robertson, 2000). Further work has examined spatial updating in locomotion (Farrell, Robertson, & Thomson, in press). Given the co-occurrence of visual neglect with basic sensory loss, demonstration of higher level representational deficits can be difficult. This work, in focusing on processes that can operate independently of vision, offers important theoretical and clinical advances in understanding normal and pathological function.

Unilateral neglect can operate within different spatial frames of reference (e.g. Driver & Halligan, 1991; Halligan & Marshall, 1991). However, most clinical assessment relies exclusively on visual tasks performed within extrapersonal space. Work has continued to develop improved assessment techniques, including assessment of neglect for the body (Beschin & Robertson, 1997; McIntosh, Brodie, Beschin, & Robertson, 2000) and practical means of dissociating attentional from basic perceptual factors (Edgworth, Robertson, & MacMillan, 1998).

A2.4 Frames of reference, perceptual input, and imagery
Scientific direction: Marcel (10%)
Grant supported posts and visitors: Dobel

Any spatial representation is with regard to a particular frame of reference. In normal sensory perception a number of representations are computed differing in reference frame, supposedly starting from one that is based on receptor surface, eg. retinotopic, eventually encompassing egocentric, and possibly geocentric, allocentric, object-centred and body-centred. A powerful confusion error of self-location has been discovered where people lose the appropriate egocentric frame of reference (Marcel & Dobel, in press). If people are blindfolded and asked to point to two previously located reference points on the walls of the room they are in, in most subjects the angle between the arms reflects the axes of symmetry relating the relevant walls (i.e. 180 or 90 degrees, depending on whether points are located on opposite or adjacent walls), an answer which neglects the person's own position relative to the reference points (see Figure A2.1). When asked why, subjects justify their answer by logical necessity ("It must be: they're opposite each other/in adjacent walls"). This persists even when subjects know that they are not near the room's axes of symmetry. The same behaviour happens when people are asked to imagine the situation. The conditions under which this phenomenon occurs and is prevented suggest that being in perceptual contact with a structured perceptual world maintains a normally dominant egocentric reference frame, and that this obtains irrespective of whichever sensory modality is operative, certainly vision and touch. Deprived of such perceptual contact (eg. by being blindfolded, losing a sensory modality, engaging in imagery, absence of perceivable environmental structure), people are subject to delusions of self-location, i.e. their location in relation to features of the environment, whereby structural descriptions of their body and their environment are mistakenly defaulted to and relied on. Work on blindsight (Marcel, 1998; Weiskrantz, 1986) suggests that this effect of perceptual contact does not rely on conscious perception, since people with blindsight are able to point to and grasp objects displayed in the blind field, which relies on an egocentric reference frame.

Figure A2.1 Room showing reference points (RPs) and axes of symmetry.Blindfolded subjects point to (a) where they think one RP is; and then (b) where they think the other RP is.

A2.5 Somatic attention: neglect, vision, and frame of reference
Scientific direction: Marcel (20%)
Other MRC posts: Cox (80%), Gillmeister (80%), Postma (80%) (1 year each)
Grant-supported posts and visitors: Rorden

Several lines of research have been pursued and new ones opened up in the area of somatic attention. We aimed to develop a differential diagnostic test for somatic neglect. Current tests either (a) use grasping of the affected limb by the intact one, and thus rely on motor performance and external spatial representation of the body, or (b) use detection of single or bilateral tactile stimuli, and thus cannot distinguish neglect from hemianaesthesia or extinction. We sought to use the influence of undetected tactile stimuli to the affected side of the body on performance related to the intact side. Adapting methods from Driver and Grossenbacher (1996), we studied interference from tactile stimuli on the affected hand on speeded tactile discrimination on the attended intact hand. Assessment of validity and generality in patients with neglect and hemisomaesthesia and control patients is being conducted in collaboration with Dr E. Ládavas (Bologna).

A set of experiments using this procedure with normal subjects has shown that a proportion of neurologically intact people show persistent experiential mislocation of salient stimuli from the unattended hand to the attended hand. The proportion showing this is similar to that of parietal patients showing allochiria (experiential displacement of stimuli or sensations from contralesional to ipsilesional locations). Our data suggest two things. (a) At least some neglect and extinction is due not to unawareness of the affected stimuli but to awareness of them at locations occupied by stimuli on the intact side of space. This is consistent with recent finding in neglect patients (see A2.2) that perseverative cancellation of targets on the right is reduced by removal of targets on the left. (b) Since an appropriate proportion of normal people show similar allochiric phenomena, such effects in patients may be due to individual differences in premorbid susceptibility. In recently completed and ongoing experiments we have shown that such effects are underlain in relevant subjects by fusion of bilateral tactile stimuli analogous to auditory phenomena (the first observation of tactile fusion). We are currently investigating the extent to which this individual difference is transmodal or modality-specific, by assessing whether the relevant individuals show an equivalent differential tendency to fusion effects in vision and audition. We are also investigating whether such fusion is affected by tactile "streaming". We are doing so by studying (a) effects of a/synchrony of fusing stimuli, and (b) whether the unattended stimulus can be captured into and kept in a separate stream by presentation of a preceding and following sequence of stimuli on that side.

Using the same procedure of tactile discrimination on one hand with congruent, incongruent or no stimuli on the other, we have partially replicated and extended Driver and Grossenbacher's study to assess the effects on distraction and interference of orientation of head and eyes to the attended versus unattended hand and that of vision of these body parts (eyes open or shut). In Driver and Grossenbacher's study seeing one or other hand had no effect, while orientation toward the attended or unattended hand interacted with hand separation. In contrast, in our study seeing one or other hand produced a significant interaction with interference, while head and eye orientation per se to either hand was ineffective. Thus, differential orientation with eyes closed was without effect. However, seeing the attended hand led to least distraction from unattended stimuli and least interference from incongruent stimuli, while seeing the unattended hand led to most distraction and most interference. It appears that seeing a body part increases the dominance of tactile stimuli on that body part for attention (consistent with Kennett, Taylor-Clarke & Haggard, 2001), while orientation per se does not. We intend to disentangle whether these effects are due to vision of the location or of the body part itself by manipulating visual perception of a video monitor per se in the location of the stimulated body part or of that bodypart displayed on the monitor either in its appropriate location or in other locations (see Proposals, A4.6).

We have used this procedure to investigate the involvement of different spatial frames of reference in somatic attention and interference. While the subject makes speeded discriminations of tactile stimuli on one hand or other body part, simultaneous stimuli (congruent or incongruent) are presented on another bodypart that is (a) contralaterally homologous or not, (b) on the same or opposite side of the body, or at varying distances either (c) in external space or (d) in somatic space. The last two factors were manipulated independently by varying arm and leg positions. Somatic distance (e.g. target: hand; distraction: ipsilateral arm, foot, contralateral arm, hand, foot) and same/different side had no effect on interference and produced no interaction. External distance had a small but inconsistent effect, but the major interference was from the contralaterally homologous body part. The fact that somatic homology and external distance did not interact is consistent with their affecting different levels. However, whether frames of reference interact in attention may depend on whether they are integrated, and which reference frames have to be integrated ought to depend on the nature of the task. An itch can be somatically located without dispositional proprioception (e.g. by IW who lacks proprioception, see project A4.3), but scratching it requires knowing its external location.

A2.6 Phenomenal and functional aspects of imagery for manual posture
Scientific direction: Marcel (15%)
Other MRC posts: Cox (20%), Gillmeister (10%) (1 year each)

We have addressed a different aspect of spatial representation of the body and its relation to neglect by investigating identification of left/right hands displayed visually at various orientations. In normal subjects latency was affected by orientation, the longest being to depiction of the most mechanically difficult posture, and immobilising one hand delayed identification selectively to depictions of that hand, suggesting the role of kinaesthetic or motor imagery. In collaboration with Drs Bisiach, Nico, Antonucci and Pizzamiglio in Italy, we used this procedure with patients with right hemisphere lesions with and without neglect and with and without unilateral plegia and loss of sensation, also investigating the effect of immobilising the intact hand to assess whether representation of the affected hand can be employed. The results indicate that patients with unilateral somatic neglect, but not those with severe unilateral motor or sensory loss, can perform the task and are able to manipulate imagery of their affected hand (i.e. when the other hand is immobilised) even when they are not conscious of proprioception. However, patients with neglect are selectively unable to use visual or kinaesthetic imagery of their affected hand to identify the orientation that is most difficult to achieve mechanically. These data suggest a dissociation of phenomenal and functional aspects of somatic imagery and suggest that neglect has a particular effect on kinesthetic spatial imagery.

A2.7 Auditory aspects of unilateral neglect
Scientific direction: Carlyon (10%), Cusack (15%), Robertson (5%)

Taking advantage of the expertise on auditory processing at the Unit, neglect patients' abnormalities in auditory attention have also been examined. Cusack, Carlyon and Robertson (2000) found that right hemisphere patients, diagnosed with neglect on the basis of performance on visual tasks, showed a curious attentional deficit in auditory processing - even when judgements were made exclusively on sounds presented to the midline. When asked to judge whether a tone's frequency was modulated (a 'warble' sound) or fixed, the patients performed as well as controls. When, however, the judgement was of relative pitch of two sounds separated by a brief interval, patients were grossly impaired. As the frequency judgement was directly equivalent in the two cases (and total duration was controlled), the impairment suggests a deficit in making "between object" comparisons. The defect was not specific to changes in frequency; patients were impaired at judging which of three sounds, presented close to midline, occupied a different location from the other two, but were intact at judging the location of single sounds. Once more, conclusions are reminiscent of object-based models of visual attention, and the integrated competition view (Project A1). In this case, however, the distribution of information is temporal rather than spatial - and further indicates the association between the neglect syndrome and much more widespread attentional impairment.

As with vision, examination of auditory attentional deficits may be contaminated by co-existing perceptual loss. Using noise burst stimuli with variable inter-aural delays (which perceptually have the effect of locating the sound more to one side of space than the other) the point of subjective midline was calculated for RH patients with neglect and hearing/age matched controls. In contrast to some other studies on the topic, no consistent bias towards hearing sounds as originating within right space was observed (Cusack, Carlyon, & Robertson, 2001). However, attentional effects associated with a sound's perceived origin within left space have been demonstrated. When healthy participants are exposed to a repeating sequence of tones (low high low - low high low) - and depending on the precise frequency difference between the tones - they will generally initially experience the sequence as a single "galloping" rhythm. Over time, however, the sequence tends to become separated into two "streams" - a repeating low tone pattern and a repeating high tone pattern. By presenting the sequence monaurally to healthy subjects and manipulating the presence of a distractor task at the other ear, Carlyon et al. were able to demonstrate the modulatory effects of attention on the segregation process (see Project A3). Consistent with this view, right hemisphere patients showed markedly different segregation functions in streams presented to the left ear in comparison to those presented to the right - which did not differ from those of controls (Carlyon, Cusack, Foxton, & Robertson, 2001). This finding invalidates models of auditory streaming based solely on brainstem processes (Beauvois and Meddis, 1991), and suggests that neglect patients may perceive complex auditory sequences (such as mixtures of two voices) differently when the talkers are on the left than when they are on the right.

A2.8 Scene representation
Scientific direction: Epstein (2 years, 70%)

Epstein has been pursuing studies of the cortical basis of navigationally-relevant spatial representations in humans. In earlier work, he demonstrated the existence of a region in parahippocampal cortex (the "parahippocampal place area", or PPA) that responded preferentially in fMRI to stimuli that convey information about the spatial structure of surrounding space (i.e. visual scenes). In a neuropsychological follow-up (Epstein et al., 2001) he demonstrated that patients with damage to this region exhibit profound difficulties in learning new environments. Furthermore, they exhibit a visual learning deficit that is specific for scene-like but not object-like stimuli, a result that was predicted from the fMRI data. Subsequent studies performed in collaboration with Dr Kim Graham and the staff of the fMRIB Centre in Oxford examined whether this region supported egocentric (observer-centered) or allocentric (world-centered) spatial representations (Epstein, Graham & Downing, submitted). An event-related adaptation paradigm was used in which fMRI response was measured in the PPA while subjects viewed events consisting of the sequential presentation of two photographs of tabletop scenes. The photographs could either depict entirely different scenes, the same scene from different viewpoints, or the same scene containing different objects. Strikingly, the response in the viewpoint change condition was exactly equivalent to the response in the different-scene condition (and significantly higher than the response in the object-change condition). These results demonstrate that the PPA considers two photographs of the same spatial layout taken from different viewpoints to be as representationally distinct as two photographs depicting entirely different tabletop layouts, and suggest that the PPA represents space in egocentric (viewer-centered) coordinates. These results provide an interesting contrast to neurophysiological studies from the rat indicating that the hippocampus supports an allocentric representation of space (the cognitive map of O'Keefe and Nadel, 1978) and argue for an entirely distinct spatial map in the PPA.

Project A3: Auditory scene analysis and the perceptual representation of sound.

When someone is faced with the task of attending to a single voice in the presence of a competing talker, they must perform a number of highly sophisticated operations. The most important of these may be summarised as follows: (i) At any one time, the outputs of the early frequency analyses performed in the two inner ears must be "parsed", so that the frequency components arising from each voice are grouped together, and are segregated from those of the other voice, (ii) the target voice must be tracked over time, (iii) decisions must be made on how to interpret "missing data", such as when part of the speech is masked by an extraneous noise, (iv) the target voice must be selected (by attentional mechanisms) for further processing, and (v) linguistic analyses must be performed on the selected voice. The first three in the list can be collectively termed "auditory scene analysis" or ASA (Bregman, 1990), and are in many ways analogous to segregation of visual input into discrete objects, a basic aspect of object-based attentional theories (Project A1). Traditionally, the different auditory processes have been studied largely in isolation, and, in particular, ASA is commonly studied separately from attentional and linguistic analyses. Furthermore, with few exceptions, the ASA studies have typically relied on behavioural measures obtained with very simple stimuli played to normal subjects. Although this approach has produced a wealth of evidence on the stimulus parameters that the brain can and cannot exploit when analysing an auditory scene, it has provided little information on the neural bases for this analysis, nor on its relationship to more cognitive processes. Our strategy has been to bridge this gap using the wide range of techniques and subject populations that are available at the CBU and elsewhere in Cambridge. In doing so, we have aimed to provide new insights not just into ASA, but also into higher-level cognitive processes. In addition to behavioral studies of scene analysis which have incorporated attentional and speech tasks, the neural bases of selective auditory processing have been studied using EEG (with Pulvermüller) and fMRI (Johnsrude). Further insights were obtained by testing stroke patients suffering from unilateral neglect (with Robertson), and deaf patients fitted with a cochlear implant (with Baguley and colleagues at Addenbrooke's hospital).

A3.1 Auditory streaming and attention
Scientific direction: Carlyon (15%), Cusack (15%)
Other MRC posts: Deeks (30%)

A simple view of the relationship between ASA and attention is that low-level mechanisms automatically parse the acoustic input into auditory objects, which are then selected by higher-level and entirely separate attentional processes. However, we have shown that attention is crucial for one aspect of ASA, namely the build-up of "auditory streaming". Carlyon, Cusack, Foxton, and Robertson (2001a) presented normal listeners with a sequence of tones of frequencies A and B, in a series of repeating triplets "ABA-ABA-ABA…" (the dashes represent silent intervals). When the frequencies of A and B are similar, or the presentation rate is slow, subjects typically report hearing all the tones in a single auditory stream, with a galloping rhythm. In contrast, when the A and B frequencies are far apart, and/or the presentation rate is fast, the "A" and "B" tones stream apart, and the percept of the galloping rhythm is lost. This paradigm measures a phenomenon that is widely used by composers of polyphonic music, and which forms the basis of our ability to track one speaker in the presence of interfering speech. In the Carlyon et al. (2001a) study, we exploited another aspect of the phenomenon, which is that the tendency to hear two streams builds up during the sequence. We presented a 20-sec. sequence to one ear and, in condition 1, asked subjects to continually judge the number of streams heard. As expected, the number of "two stream" judgements increased over time. In a second condition, we asked subjects to perform a competing task on a sequence of noises presented to their other ear during the first 10 sec of the tone sequence, after which time they were required to switch attention to the tones and to start making the streaming judgements about the last 10 sec. The key finding was that the proportion of "two stream" judgements made shortly after the switch was similar to the proportion at the beginning of the sequence in condition 1, and much lower than that observed after 10 sec in that condition. Hence, by manipulating attention during the first half of a sequence, we affected streaming during the second half. A second experiment showed that performing a competing task on the same sequences as those on which streaming judgements were to be made did not reduce the build-up. Combined with our recent finding (Cusack, Deeks, Aikman, & Carlyon, submitted) that build-up is reduced by a competing task performed on different sounds presented to the same ear as the target stream, this indicates that the build up of streaming depends on whether one attends to a particular auditory object, rather than on whether one performs a particular task or attends to a spatial location. An additional finding is that the build-up of streaming can be inhibited by a visual competing task, providing evidence for a supra-modal attentional limitation (c.f. Arnell & Jolicoeur, 1999). Further evidence for a supra-modal attentional influence on ASA came from streaming judgements of sequences presented to the left and right ears of patients suffering from unilateral neglect of stimuli on the left side of space, as diagnosed on the basis of visual tasks (see Project A2). These patients showed less streaming of sequences presented to their left ears than of sequences presented to their right ears, or to either ear of controls. Finally, we have shown that, if streaming is allowed to build up, then it can be largely abolished by either turning the sequence off for a few seconds, or, equally, by requiring subjects to perform a competing task for a few seconds. This is consistent with the idea that the act of switching attention may "reset" the streaming mechanism.

It should be stressed that the conclusion that the build-up of auditory streaming is dependent on attention does not necessarily apply to other aspects of ASA. Indeed, our finding that attending to a competing stimulus can inhibit the build-up is consistent with that stimulus having been segregated from the tone sequence by pre-attentive mechanisms. We have suggested (Carlyon et al., 2001a) that perceptual segregation of sounds that start and stop at different times ("grouping by common onset") is one such pre-attentive form of ASA.

A3.2 Perceptual asymmetries
Scientific direction: Cusack (15%), Carlyon (7.5%)

In the visual modality, striking perceptual asymmetries are observed when a subject is required to select a target from a background of distracting stimuli. For example, the time taken to identify a "Q" against a background of "O"s is substantially faster than that taken to identify an "O" against a background of "Q"s. One of the first explanations, which is still extremely influential (Triesman & Gormican, 1988), asserted that early in visual processing, we form a number of separate feature maps. If the target uniquely contains a feature, such as the straight line that forms the tail of a "Q", then the entire array of detectors for this feature may be examined in parallel. Conversely, if the target is defined by the absence of a feature, then the task is much harder, and a serial search is required. Although the precise mechanisms underlying these asymmetries are still the subject of some debate, it remains true that the presence or absence of visual features can have a strong effect on performance. In contrast, there has been little research on the presence or absence of features, or indeed any evidence for perceptual asymmetries, in the auditory domain.

Using an analogue of visual search tasks, we have provided evidence that frequency modulation ("FM") is an auditory feature (Cusack and Carlyon, in press). In one experiment, we presented subjects with a sequence of tones that were quasi-randomly distributed in time and frequency. In one condition (Fig A3.1, top), a single modulated target was presented (on 50% of trials) against a background of steady tones, and subjects were asked to report whether a "wobbling" tone was present. Performance in this condition was substantially better than when the non-targets were FM tones and subjects had to detect a single steady tone (Fig. A3.1, bottom). Furthermore, we obtained an analogous pattern of results using a different manipulation, in which subjects were better at detecting a long-duration tone against a background of shorter tones than vice versa. This is consistent with evidence from the visual modality of better detection for a stimulus with "more of" a feature against a background of stimuli containing "less of" that feature (e.g. a long line against a background of shorter lines) than vice versa (Beck, 1982).

Figure A3.1



A3.3 Effects of attention and grouping in auditory cortex
Scientific direction: Cusack (15%), Carlyon (7.5%), Johnsrude (5%)

We have used fMRI to investigate the effects of auditory grouping and attention on activation of auditory cortex (Cusack, Carlyon, Johnsrude, & Epstein, 2001). We either presented a single sequence of tones heard towards the left or right, or two interleaved sequences, one heard on each side. The tones could be made to appear on one side either by presenting them to one ear only, or by presenting them binaurally such that they lagged slightly in one ear; this caused them to be heard on the non-lagging side. Subjects were instructed to detect a rising pattern of tones on either the left or right side of the head. The task instructions had no effect on the relative amount of activation on the left or right side. However, greater activation was found for two monotic sequences that alternated between the ears than for a single binaural sequence, even though in these two conditions the total amount of energy presented to each ear was identical. One interpretation of this finding, which we intend to pursue in the next quinquennium, is that activation of auditory cortex is modified by the number of "auditory objects" perceived, which was greater in the "alternating between ears" than in the binaural condition. If so, then the fact that these effects can be measured in auditory cortex would confirm our interpretation of one of our behavioural streaming experiments, which is that grouping by common onset occurs at an early, pre-attentive stage of auditory processing (see above).

A3.4 The continuity illusion
Scientific direction: Carlyon (20%), Pulvermüller (5%)
Other MRC posts: Deeks (40%), Shtyrov (5%)
CBU collaborators: Norris, Butterfield, Hauk
Grant-supported scientists and visitors: Micheyl

When a sound is turned off briefly and then on again, it can be perceived as continuous when the silent gap is filled by an "inducing" sound, such as a burst of noise. This "continuity illusion" only occurs if the frequency content and timing of the noise is such that it could have plausibly masked the sound had it remained uninterrupted. It is important for the perception of stimuli such as speech in noisy environments; for example, if a sound such as /i/ is masked mid-way through by a brief sound, it would not make sense to interpret it as two separate phonemes separated by a gap. Most previous studies of the illusion have relied solely on subjective reports, which, we have argued (Carlyon, Deeks, Norris, & Butterfield, 2002a), do not distinguish even between broad classes of explanation for the effect. For example, if a subject reports a tone interrupted by a noise as being continuous, then at least two explanations are possible. At one extreme, s/he could reason that the tone ended at particular time and frequency, reappeared later at the same frequency, and conclude that it "must have" continued behind the noise. At the opposite extreme, it could be that, during the illusion, the firing pattern of neurons, perhaps at a fairly peripheral stage of auditory processing, resembles that which would have occurred had the "inducee" been physically present. We performed two studies, both of which imposed constraints on the possible level of processing at which the effect occurs.

A3.4.1 Influence on vowel identification

We have shown that the mechanisms responsible for the continuity illusion "feed into" those involved in vowel identification (Carlyon et al., 2002a). Subjects were required to identify a two-formant vowel under a number of conditions. When the formants were presented simultaneously and pulsed on and off together, identification was very good, but became poor when the formants were alternated in time. In the most important condition, the formants were alternated, but the gaps in the upper formant were filled with high-frequency noise, and those in the lower formant region were filled with low-frequency noise. This caused the formants to be perceived as continuous and hence as simultaneous with each other, and led to a substantial increase in performance. This finding not only provided a performance measure of the illusion, inconsistent with "cognitive re-interpretation" explanations, but also showed that accurate vowel identification does not require formants to be physically simultaneous.

A3.4.2 An electrophysiological correlate of the continuity illusion

We have recently obtained a neurophysiological measure of the continuity illusion (Micheyl et al., in press). The mismatch negativity (MMN) is a negative deviation in the EEG response to a rare "deviant" sound presented in a sequence of more frequent "standards". It can be obtained when subjects are instructed to ignore the sounds and to attend instead to a visual stimulus – which, in our study, was a silent video. We measured the MMN to a deviant that consisted of an interrupted tone in which the silent gap was filled either with an "on frequency" noise, which induced the illusion of continuity, or with an "off frequency noise", which did not. When the standards consisted of continuous tones the MMN was larger when the deviant was perceived as interrupted (off-frequency noise; condition 2b, Fig. A3.2) than when it was heard as continuous (on-frequency noise, condition 2a). Conversely, when we used interrupted tones as standards, the MMN was larger when the deviants were perceived as continuous (on-frequency noise, condition 1a) than when heard as interrupted (off-frequency noise, condition 1b). Note that, by measuring an interaction between standard and deviant type, the study controlled for any "coincidental" differences between ability of particular standards or deviants to elicit MMNs. Hence we have demonstrated that the continuity illusion can be observed objectively in a situation where subjects do not focus attention on the sounds, and where no response is required. Furthermore, the latency (<240 ms) and neural locus (around auditory cortex) of the MMN provide strong evidence against "late re-interpretation" explanations for the phenomenon.

Figure A3.2 Subjects heard a sequence consisting of common (80%)"standard" tones (two shown for each condition) and rare (20%) "deviants" (one shown per condition). Each deviant was an interrupted tone accompanied by a band of noise. Noise bands were also interspersed between the tones.

A3.5 ASA by cochlear implant users
Scientific direction: Carlyon (20%)
Other MRC posts: Deeks (15%)
Grant-supported scientists and visitors: Long

The cochlear implant is the first ever successful sensory-neural prosthesis. We have recently developed the technical capability and clinical contacts to study ASA in implant users in association with colleagues at Addenbrooke's hospital, Cambridge, as well as continuing experiments with overseas collaborators (C. McKay and H. McDermott in Australia, J. Wouters and A. van Wieringen in Belgium). These experiments allow us to address a clinically important question, while permitting attacks on basic scientific issues that are impenetrable with normal, acoustic stimulation.

The clinical issue arises from the fact that implant users can often understand speech in quiet, but have great difficulty in noisy situations. An example of a basic scientific issue is the extent to which listeners can use purely temporal information to segregate concurrent sounds. In normal hearing, sounds of different frequencies produce different temporal patterns of firing in the auditory nerve, but usually also excite different neural populations. Hence, if a subject can hear one sound in the presence of the other, it is hard to tell whether s/he is using the temporal or the place-of-excitation information to do so. In an implant, however, one can easily separate the temporal and place-of-excitation factors. This is possible because the implant consists of an array of electrodes distributed along the length of the cochlea, so one can vary place-of-excitation by manipulating which electrode(s) is stimulated, and manipulate temporal cues by, for example, selecting a single electrode channel and varying the temporal pattern of impulses applied to that channel. We have played mixtures of regular pulse trains to a single channel, and determined whether cochlear implantees can hear the two underlying pitches, or whether they hear a single, undifferentiated pitch. The results show that, when a pulse train of a given "carrier" frequency is modulated at a much slower rate, patients can indeed extract the pitches corresponding to both the carrier and modulation rates (McKay & Carlyon, 1999). This is the sort of pattern that occurs in the outputs of modern cochlear-implant speech-processing schemes, such as the widely used "continuous interleaved sampling" algorithm, when presented with a single voice; the modulation rate corresponds to the voice pitch and the carrier rate is fixed. However, when two harmonically unrelated pulse trains are mixed, patients hear a single, somewhat rough, pitch, corresponding to the rate of the higher-rate pulse train (Carlyon, van Wieringen, Long, Deeks, & Wouters, 2002b; Long, Carlyon, McKay, & Vanat, 2001; van Wieringen, Carlyon, Long, & Wouters, 2002). We have shown that these results, as well as those obtained with our acoustic simulations of cochlear implant hearing (see below), can be captured by a simple model of pitch perception; this model also accounts for a range of findings that are inconsistent with the most popular "autocorrelation" class of pitch models. The findings and the model indicate that a) current cochlear implant processing strategies do not allow users to exploit pitch differences between different voices to segregate them from each other, and b) neither implantees nor normal listeners can use purely temporal information to segregate concurrent sounds, in the absence of the "place of excitation" cues that are produced by pitch differences.

We have also investigated whether implant patients are sensitive to another class of potential ASA cues, arising from differences in the temporal pattern of stimulation on different electrodes (Carlyon, Geurts, & Wouters, 2000). If patients could use these cues, this might allow them, for example, to segregate one formant of one speaker's voice from a different formant of another voice. We showed that patients could sometimes detect very small (<100μsec) delays between two pulse trains applied to different electrodes that stimulated quite different populations of auditory nerve fibres. However, performance on this task was quite variable and depended idiosyncratically on which electrode was delayed, suggesting that these small asynchronies are unlikely to provide a firm basis for sound segregation. Importantly, though, it was unaffected by the presentation of another pattern of stimulation on an intermediate electrode, when this stimulation started 400 ms before, and ended 400 ms after, that on the two electrodes to be compared. We attributed patients' resilience to this potentially interfering stimulation to the fact that the onset and offset asynchrony caused it to fall into a separate "auditory stream" from that on the target electrodes. We will be further testing this interpretation in the next quinqennium; if verified, it will be the first demonstration of the perceptual segregation of concurrent stimuli by cochlear implant users.

Finally, in parallel with our experiments with implant users, we have developed an acoustic approximation to electrical stimulation that can be used with normally hearing listeners. By bandpass filtering acoustic pulse trains in a frequency region that is high relative to the repetition rate of that train, it is possible to vary the temporal patterns of stimulation without giving rise to cues based on the place of excitation on the basilar membrane. This produces results very similar to those obtained by manipulating the temporal parameters of a pulse train applied to a single channel of a cochlear implant (Carlyon et al., 2002b; Long et al., 2001; McKay & Carlyon, 1999; van Wieringen et al., 2002). It allows us and other experimenters to pilot implant experiments with a homogenous and readily-available population of normal listeners. Perhaps more importantly, it adds power to our experiments by excluding alternative explanations that are specific either to acoustic or electrical stimulation.

A3.6 Psychoacoustics of fundamental basic auditory processes, and applications to special populations
Scientific direction: Carlyon (20%)
Other MRC posts: Deeks (15%)
Grant-supported posts and visitors: Gockel, Micheyl, Lyzenga

Carlyon's research into more basic auditory processes has continued in collaboration with Prof. B.C.J. Moore (Cambridge) and with external funding from the Wellcome Trust and the EPSRC. It has provided new information that is additionally relevant to cochlear implant design. For example, we have shown that auditory processing of temporal information is "sluggish" (Carlyon, Moore, & Micheyl, 2000; Gockel, Carlyon, & Micheyl, 1999; Gockel, Moore, & Carlyon, 2001; Micheyl & Carlyon, 1998), suggesting that that the usefulness of pitch ("fundamental frequency, F0") information by cochlear implant users may be severely limited when F0 changes over time. This limitation would occur because modern implants code F0 in purely temporal terms. For example, we have shown that when the pitch of a sound is encoded only by temporal cues, one's estimate of that pitch is severely disrupted by subsequent and preceding sounds, even when they have a quite different F0 (Gockel et al., 1999; Micheyl & Carlyon, 1998). We have also developed a model of how listeners perceive the pitch of a sound whose frequency is changing rapidly over time (Gockel et al., 2001). In addition, a collaboration with Prof. S. Shamma (Univ. Maryland) has led to a new model of normal listeners' sensitivity to timing differences between frequency regions (Carlyon & Shamma, 2002), which has implications for across-channel timing sensitivity of cochlear implant users.

Another strand of our research concerns the independence of processing of location from other aspects of auditory perception (cf. proposal section SL2). In one study, we presented listeners with filtered pulse trains similar to those described above (A3.5), except that they were presented dichotically (Carlyon, Demany, and Deeks, 2001c). The perceived location of such dichotic pulse trains, presented over headphones, can be manipulated by varying the interaural time difference (ITD) between the pulses applied to each ear. In one crucial condition, we presented subjects with a pulse train that started off leading on the left ear, and was therefore heard on the left with a pitch equal to the pulse rate (200 Hz). Halfway through the sound, we switched the ITD of every other pulse pair, so that they led on the right (dashed lines in Fig. A3.3). Accordingly, subjects heard a new pulse train near the right ear. Importantly, though, the pitch they heard did not drop by an octave, as would be expected if they had segregated every other pair of dichotic pulses, assigned them to a new location, and then estimated the pitch of this segregated pulse train. Instead, the pitch remained unchanged (at 200 Hz), indicating that pitch was estimated from the rate of pulses arriving at each ear, whereas location was derived from the interaural timing relationship of the pulses. Another study showed that the detection of mistuning was also affected by "ear of entry", and not by the perceived location of the mistuned component relative to the rest of a complex tone (Gockel & Carlyon, 1998).

Fig. 3: Pulse trains used by Carlyon et al. (2001b). The repetition rate of the sound in the new location (dashed lines) is ½ that of the original sound, but its pitch did not drop substantially

Two further findings are worthy of particular mention. First, we have shown that stimuli with identical long-term power spectra, but which produce temporal patterns of stimulation of the basilar membrane that differ markedly in their peak factor ("peakiness"), can produce markedly different amounts of average excitation (Carlyon & Datta, 1997). This finding, obtained with forward masking and loudness-balancing procedures, reflects the fact that the peakier basilar membrane response is subjected to a greater degree of peripheral compression. It provides convincing evidence that peripheral compression acts on a fast time scale (faster than the 10-ms period of the fluctuations). Second, together with Prof. D. Bishop, we have provided evidence that specific language impairment in children is unlikely to be dependent on the child having a basic temporal processing deficit (Bishop, Carlyon, Deeks, & Bishop, 1999). This research, which won a "best paper" award from the journal in which it was published, has not been pursued since Prof. Bishop's move to the University of Oxford.

Project A4: Attention, consciousness and the body.

Consciousness and attention have long been intimately linked. This project explores that link by conceptual and empirical study of aspects of each that are often ignored. Generally, cognitive treatment of consciousness focusses on what is nonconscious rather than conscious, on formal features more than content, on external perception rather than experience of emotion, action or other aspects of the body or self; it largely ignores features that are so pervasive they escape notice, and it makes major ungrounded assumptions. In this period these neglected topics have continued to be pursued or are newly addressed, and the role of the body and space in consciousness has been emphasised.

Recent work challenges usual assumptions about unity of consciousness: (a) there is a single level of consciousness: if one has a phenomenal experience then one is aware of it and can report it; (b) there is (except perhaps in split-brain) only one consciousness per person: one cannot at one time experience both something and its contradiction; (c) the contents of one consciousness are integrated temporally and spatially, and if not we would notice. Studies of emotion experience, anosognosia for plegia, blindsight and unawareness of blindness (Lambie & Marcel, 2002; Marcel, 1998; Marcel et al., in press) have suggested two disunities: (i) Two levels of consciousness, 1st-order, phenomenal experience (qualitative representation, "what it's like") distinct from 2nd-order awareness of such experience, the latter being a function of attention and the basis of report and explicit episodic memory. (A pain in a body part attracts attention in virtue of its hedonic quality, but the attention creates awareness of it. In driving a known route while listening to the radio, the phenomenology of the driving exists but without 2nd-order awareness until attention is required). (See A4.4, A4.5). (ii) Disunity within each level: 1st-order experience is only locally unified and can be inconsistent; 2nd-order awareness can be dissociatively split into co-synchronous consciousnesses (Gallagher & Marcel, 1999; Marcel, 2000; Marcel, in press - a, b) (see A4.1). Two disregarded aspects of attention have been invoked as influencing the content and nature of consciousness: (i) attentional "mode", whether attention is detached or immersed, analytic or synthetic, and (ii) self- vs world-focus. Differences in the mode of attention have been used to account for abnormal states in anosognosia for plegia (Marcel et al., in press), for the sense of ownership/disownership of actions, bodyparts and tactile sensation (Marcel, in press - b), variations in emotion experience and hedonics, and the so-called "hard problem" – phenomenology itself (Lambie & Marcel, 2002). Self-/world-focus determines what one is focally aware of in emotion, in tactile experience, and in more general spatial experience.

Bodily experience plays an important role in gaining a sense of self, in emotion and in spatiality (Bermúdez, Marcel & Eilan, 1995; Lambie & Marcel, 2002; Marcel, in press - b). Work in this project and in A2 focusses on bodily spatiality, movement, awareness of them, and their role in emotion. First, conscious experience of bodily disposition has been shown to be qualitatively different from its corresponding nonconscious representation, both in use of kinesthetic imagery in recognition of bodyparts and in coding of disposition and location of limbs in control and awareness of action. Second, the content of perceptual consciousness depends on attention to the world or the body, one being spatial ground to the other as figure; and focal attention can be directed to parts of body space as to parts of external space. These foci of attention involve different spatial frames of reference, e.g. somatotopic vs egocentric (Marcel, submitted; Marcel & Dobel, in press). Thus, in touch attention determines whether the afferent information is experienced as tactile sensation at a somatic location or haptic perception of an object in egocentric space. This distinction is supported by our research on divided attention to points in somatotopic and external space. Several frames of reference are computed in perception and normally have to be integrated, e.g. in visually guided manipulation. However, in consciousness only one can be dominant at a time (Marcel, submitted; Marcel & Dobel, in press). Aspects of this are also explored in the work on somatic attention and neglect (Project A2.5).

A4.1 Anosognosia for plegia: Disunity of bodily unawareness
Scientific direction: Marcel (15%)
Other MRC posts: Postma (20%)

In anosognosia for plegia patients are unaware of their motor impairment. This topic is important for clinical practice as well as theoretically, since presence of unawareness of a deficit is the greatest impediment to rehabilitation. Joint research with Tegnér (Marcel et al., in press) that was large-scale in terms of number of patients and novel in terms of the breadth and depth of testing shows that unawareness for hemiplegia separates into several kinds of deficit, some patients manifesting more than one. (i) Patients aware of having plegia are unaware of its consequences. (ii) Patients who are unable to move a limb when asked are unaware of the failure, without illusory sensation of movement. (iii) Patients are concurrently aware of movement failures and can access episodic memory of these but are unable to update generic long-term body knowledge. (iv) Patients' awareness/unawareness of their limb paralysis or ability on bimanual tasks depends on manner of questioning ("Is this arm weak/Is this arm ever naughty?"; "In your present condition…/ If I were in your present condition…"), and they have a deficit of pragmatics and unconstrained confabulation specific to the affected limb(s). This is particular to right hemisphere damage, and it demonstrates disunified and split consciousness. A major thrust of this research is that its results undermine previous attempts to explain anosognosia for plegia in terms of a unitary deficit and indicate that it is not a matter of simple unawareness. The different forms of deficit have differential implications for rehabilitation. We are currently testing these characterisations (a) by assessing predicted differences in interference in colour-naming from plegia-related words at varying times after failed movement, (b) by comparing self-ratings with and without cued episodic recall of earlier movement failure, (c) by exploring what underlies split awareness and altered pragmatics by varying factors in the questions that elicit such dissociations and by exposing patients to their logical self-contradictions (see Proposals A4.1). We intend to develop our battery of tests into a clinical research tool.

A4.2 Conscious and nonconscious limb location and movement
Scientific direction: Marcel (15%)

A different aspect of bodily awareness is awareness of location and movement of limbs in normal people. In collaboration with Roll in Marseille, we have used vibrotactile-induced illusions of bodypart location. Vibrotactile stimulation of muscle spindle receptors at a joint produces illusory felt movement and corresponding illusory location of the limb if the limb is held stationary. With vision occluded, reports of and manual pointing to the felt location of the hand of the stimulated arm confirm the illusory displacement; yet if subjects are asked to grasp the seemingly displaced hand with their other hand, they do so correctly, in its true location. If the grasp is delayed it tends to go to the illusory location. This suggests that it is a proprioceptive version of the Roelofs effect (Bridgeman, 1992), where initial eye movements and pointing are accurate and dissociated from illusory visual target movement, but follow the illusion after a delay. In a second study, when the illusorily displaced hand has to move to a visually specified target location, with the arm unseen, the movement is almost always correct in both direction and extent. However, not only the prior intention but also (for c. 70% of people) the consciously felt movement is in the opposite direction to its actual direction, ie. that appropriate to the illusion. These disparities between reported experience and action imply (i) a dissociation of conscious experience of static bodily disposition from nonconscious representation of it, and of conscious intention from nonconscious implementation and control of movement, and (ii) that most people have poor conscious access to the specific implementation of intentions for movement. The first report of this work (Marcel, in press - b) also deals with experienced dis/ownership of action and the sense of agency. It provides a novel review and integration of a variety of neurological, neuroscience, normal cognitive and clinical research. In providing an account of ownership of action, especially regarding anarchic hand syndrome, it draws on the concept of detached versus immersed attention that has been applied in our work on anosognosia, emotion experience, and self awareness (see Gallagher and Marcel, 1999, for review).

A4.3 Effects of peripheral loss of sense of touch and body position
Scientific direction: Marcel (5%)
Other MRC posts: Gillmeister (10%)

Ongoing work with Cole (Southampton) on a patient who suffered peripheral deafferentation bears on conscious versus nonconscious bodily representation, on bodily experience and on spatial representation. Although most current neuropsychological research on these issues focuses on effects of central damage, the patient concerned confirms the importance of peripheral information and illuminates its roles. Due to a peripheral neuropathy that caused demyelinisation of the large afferent fibres, IW was deprived of all proprioceptive experience and bodily sensation beneath the neck, except for deep pain and temperature at the surface (Cole, 1993). (1) In experiments involving forced-choice discrimination of touch/no touch on a specified location, of location of touch, of presence-absence and direction of passive limb movement, and of joint position, IW performed above chance, suggesting some residual nonconscious capacities subserved by the intact slow fibres. (2) In order to assess determinateness of location of sensation, since IW cannot point to his own body we have used heat stimuli and required pointing to life-size depictions of a body and same-different judgements. IW has performed remarkably well. (3) Without vision IW's actions preserve configuration but not location. We have attempted to assess the extent to which his proprioceptive loss shows the same dissociation. We compared his ability to perceive and learn configurations versus egocentric locations of raised contours of shapes and of heat spots on a surface by manual exploration without vision. Although he was unable to do the first task, he did show the dissociation in the latter (though there are memory limitations). Since apprehension of configuration in this situation relies on proprioception, this suggests that the deficiency is not in proprioception per se, but in the representation of egocentric location. This also suggests that the deficiency is to some extent restricted to proprioceptive awareness. These studies thus reveal unexpected roles of peripheral afference. Further experiments will (a) refine our procedures since conventional paradigms are unpredictably difficult for IW, and (b) examine IW's ability to distinguish self-movement from world movement via a tactile flow-field of textured surfaces.

A4.4 Consciousness and emotion experience
Scientific direction: Marcel (15%)

Most current approaches to consciousness ignore emotion and bodily experience, dealing only with cognitive perceptual awareness of the external world. Our theoretical research on consciousness has been expanded with Lambie (Cambridge) to deal with emotion experience. Considerable conceptual and review work has resulted in a recent major theoretical paper (Lambie and Marcel, 2002), that has had an impact on cognitive and emotion theory and among philosophers. We have managed to resolve previous disputes as to the content of emotion experience by acknowledging its varieties and by treating separately the content of emotion experience, the underlying nonconscious correspondences, and the processes contributing to conscious experience. The proposed principled taxonomy of the content of emotion experience depends on three aspects of attention, mode (immersed-detached; synthetic-analytic), direction (self-world) and focus (evaluation-action), and is informed by a two-level view of consciousness where phenomenology (1st-order) is distinguished from awareness (2nd-order). Representation at the nonconscious and the two conscious levels can be distinguished respectively by indirect effects, expressability and ability to report. Intentional action based on a representation requires it to have phenomenological status, but without awareness of it appropriate explanation of one's action is impossible. These distinctions enable us to separate and account for cases of "unconscious" emotion where there is an apparent lack of phenomenology or awareness. Previously there has been no principled way to distinguish lack of awareness of one's emotion in normal cases, infancy, anger disorders, prefrontal brain damage, alexithymia, panic attacks, cultural differences, and defence mechanisms such as repression and intellectualization. Particular conceptual contributions of the work include (a) the mode of attention (a dimension of attention previously largely ignored), which accounts for phenomenology and hedonicity and is applicable to certain frontal right hemisphere neurological syndromes, (b) the role of the body in self experience and in a physical approach to emotion, (c) an integration of emotion experience with cognitive psychology, cognitive neuropsychology and the phenomenological tradition. The particular contributions to consciousness are in treating consciousness as two-level, separating phenomenology from awareness, in proposing how different aspects of attention contribute to each, and in outlining a spatial distinction between (bodily) self- and world-focus. The role of attentional mode in modulating felt ownership and hedonicity promises an approach to the "hard problem", i.e. phenomenology. Predictions from the theory will continue to be tested in the next quinquennium (see Proposals A4.4).

A4.5 Blindsight and visual awareness
Scientific direction: Marcel (5%)

Work on blindsight (Marcel, 1998) has shown several things. (i) In attempts to grasp objects in the blind field, aspects of patients' preparatory hand and arm movements are differentially appropriate to the relevant features of the object (shape, size, orientation, 3D location). This implies that nonconscious spatial representation is relatively intact, rather than being restricted to egocentric location. (ii) The fact that upper-case presentation of words in the blind field primes and biases choice of words subsequently presented in the sighted field implies that structural descriptions of features (oriented strokes) are achieved and that they can access appropriate stored representations, e.g. lexical entries. The original finding has been replicated and extended to representation of and priming by pictures by Joergens, Niedeggen & Stoerig (2001). (iii) Importantly, veridical phenomenal consciousness of static stimuli in the blind field can be temporarily regained if stimuli presented to it are related by Gestalt organisation to stimuli in the sighted field (using afterimages and Kanisza figures). This not only implies that blindsight does not involve a complete loss of conscious vision, but also suggests that the loss may be due to a reduction in attentional capacity. The relation of this effect to that of contralateral stimuli in extinction suggests that bilateral interaction across occipital cortices is integrative and facilitatory while that across parietal cortices is competitive (cf. distinct roles of cooperation and competition in visual attention; Project A1). We are testing this in currently planned joint research with Kentridge and Girolamo (see Proposals A4.2).
Research on an interesting single case suggests that blindsight is a 1st-order deficit of visual phenomenology (what characterises a perceptual experience as visual rather than of another sensory modality) rather than a 2nd-order deficit of perceptual awareness of or access to such phenomenology. DC's damage resulted from traumatic bilateral impacting of the occipital poles. DC was not clinically confused and was fully aware of his slight memory impairment and his broken legs. While he acknowledged from failures in behaviour that he had visual problems, he was not aware of being blind. Intentional denial to preserve self-esteem does not account for his selective unawareness. His adequate visual imagery performance (tested by Dr B. Wilson) suggests no problem with internally generated visual experience. His impairment thus appears to be a selective failure of introspective access to lack of visual perceptual experience. The most important aspect of the case is that while being blind on conventional testing, he has blindsight when tested appropriately. He could accurately point at and grasp objects when forced to do so rapidly. While performing at chance on conventional confident binary judgements of extremes of luminance, he performed nearly perfectly in the same situation when asked to rapidly guess luminance after it was explained that difficult discriminations would be used to measure thresholds. His unawareness of his "blindness" remitted after 7 months, but he has been left with bilateral blindsight. As indicated above, this double unawareness implies two levels of consciousness. Unfortunately the depression that his condition now causes him leads to reluctance to participate in further research.

Project A5: Integration and differentiation of frontal functions.

In Project A5 we turn to control functions, and in particular the functions of prefrontal cortex. While the importance of the prefrontal cortex for higher-order cognitive functions is largely undisputed, no consensus has been reached regarding the fractionation of functions within this region. In fact, most attempts to map specific cognitive functions onto neuroanatomical and/or cytoarchitectonic sub-divisions have been disappointing. This is true, not only for data derived from human neuropsychological studies, but also from lesion and electrophysiological studies in the monkey and, more recently, from human functional neuroimaging. Although functional specialization undoubtedly exists within the frontal cortex, it is becoming clear that the structural organization of this system does not relate, in any straightforward way, to contemporary models of cognition.
Much of our research during the current funding period can be considered within this general conceptual framework and has involved, at multiple levels of analysis, attempts to identify adequate functional descriptions for specific regions within the human frontal lobe. Broadly speaking, three anatomically and cytoarchitectonically distinct frontal-lobe regions have been targeted, partly on the basis of previous work by Owen (mid-dorsolateral frontal cortex or DLPFC, comprising Brodmann areas 9 and 46; mid-ventrolateral frontal cortex or VLPFC comprising posterior areas 47 and 45) and Rogers (orbitofrontal cortex comprising Brodmann area 11), and partly on the basis of other monkey and human data suggesting some specialization of these areas in respectively executive, mnemonic and affective processes.

A5.1 The functional relationship between DLPFC and VLPFC
Scientific direction: Owen (25%)
Other MRC posts: Duncan (5%)
Grant-supported posts and visitors: Bor
Students: Bor, Lee

Perhaps the most widely debated issue to have emerged in this field in recent years concerns the functional relationship between dorsal and ventral regions of the lateral frontal cortex. One prevalent view has been that these regions differ in terms of the type (e.g. domain) of information being processed (Goldman-Rakic, 1994), with dorsolateral frontal regions being principally concerned with spatial material while ventrolateral regions preferentially process non-spatial material. Owen has combined studies in neuropsychological patients (Owen, Morris, Sahakian, Polkey, & Robbins, 1996c), with functional neuroimaging studies in healthy volunteers (e.g. Owen et al., 1997a; Owen et al., 1998b; Owen et al., 1999b; Owen, Lee, & Williams, 2000) and extensive reviews of both the functional neuroimaging (Owen 1997a; 1997b; 2000) and electrophysiological work (Rushworth & Owen, 1998) literature to refute this view in favour of a "process-specific" model of lateral frontal-lobe organisation (Petrides, 1994). According to that view, the DLPFC and VLPFC differ, not in terms of the modality of the information that is processed by these regions, but in terms of the type of processing that is carried out on that information. For example, while VLPFC but not DLPFC is activated during simple spatial (Owen et al., 1999b), digit (Owen et al., 2000) and pattern span (Stern et al., 2000) tasks, activation in both regions is observed when participants are required to manipulate that same information within memory (e.g. Owen et al., 1998b; 1999b; 2000).

Though these studies render the material-specific model untenable, they provide only preliminary hints as to what the functional contribution of DLPFC and VLPFC might actually be. For example, terms such as "manipulation" (Owen 2000) and "monitoring" (Petrides, 1994) which have been used to describe DLPFC function can be hard to define operationally, and in many studies, a complicating factor has been simple task difficulty; tasks that produce greater DLPFC activation (e.g. reverse digit span, Owen et al., 2000) tend to be more difficult than those that do not (e.g. forward digit span). This confound is important because increasing task difficulty in itself is associated with DLPFC activation in many different cognitive domains (Duncan & Owen, 2000, see A5.7).

Two PET studies in healthy controls (Bor, Duncan, & Owen, 2001) provided an interesting new approach to this problem; the results revealed that while traditional spatial span tasks (with randomly arranged unstructured arrays) typically activate the VLPFC, analogous tasks using a more structured spatial array activate both VLPFC and DLPFC. Moreover, performance on the more structured task was rather better than performance on the unstructured task suggesting a lowering of overall task demands. These studies were complemented and extended by a large-scale public science exhibit at the Science Museum in London (Bor, Duncan, & Owen., in press) involving several thousand participants. Verbal protocols suggest that, with structured arrays, there is increased reliance on array-specific encoding strategies which serve to reduce the overall load on working memory.

To test this hypothesis directly, a novel version of the spatial span task was developed to compare structured span sequences, encouraging reorganization and chunking, with unstructured sequences, using event-related fMRI (Bor et al., in press). As predicted, structured sequences led to improved performance yet, despite this reduction in task difficulty, the DLPFC and selected regions of posterior cortex were more strongly recruited (see Figure A5.1). Additional behavioral evidence from the scanned volunteers as well as thousands of participants involved in the Science Museum project suggested that this was the result of reorganizing the material to be remembered into familiar chunks. For the first time, we believe, these results show that even when memory demand decreases, organization of working memory contents into higher-level chunks is associated with increased DLPFC activity.

A5.1 Structured sequences are easier to remember than non-structured sequences yet produce significantly great activity in the lateral frontal cortex.

Convergence between functional neuroimaging and lesion studies remains a central theme in this work and the imaging results make a number of important predictions about the behaviour of frontal-lobe patients. In particular, they suggest impairments in simple working memory tasks such as spatial span, perhaps with disproportionate deficits in tasks that depend upon strategies to optimize performance. While previous work by Owen (Owen et al., 1996c) has suggested that frontal-lobe patients are particularly impaired at working memory tasks involving strategies, the existing literature on the classic spatial span task of Corsi suggests that memory tasks of this type are not impaired in such patients (e.g. Owen, Downes, Sahakian, Polkey, & Robbins, 1990). To explore the relationship between neuropsychological studies and imaging studies in healthy volunteers further, a more sensitive method for measuring spatial span was developed (Bor et al., submitted) and used to test patients from the Cambridge Cognitive Neuroscience Research Panel. Consistent with the imaging data, the preliminary results show that patients with frontal-lobe damage are indeed impaired at the more sensitive spatial span tasks, and may be disproportionately impaired when chunking strategies are available.

A5.2 The VLPFC: Unitary or multiple functions
Scientific direction: Owen (25%)
Other MRC posts: Dove (3 years, 80%)
Students: Bor

A parallel series of studies has investigated VLPFC function in detail. Earlier work by Owen using PET had suggested that reliable activation is observed in this region during tasks that require "active" retrieval of spatial information from working memory (Owen et al., 1996a; 1998b; see also Bor et al., 2001; in press). Follow-up studies confirmed that this involvement in retrieval was polymodal; identical patterns of activity were observed in this region during analogous tasks involving auditorily presented digits (Owen et al., 2000), and visually presented abstract patterns (Stern et al., 2000; Owen et al., 1998b).

On the basis of these findings, Dove and Owen have used event-related fMRI to define the specific role of this region in mnemonic processing. The results of the first study, using abstract patterns, demonstrated that VLPFC is similarly involved in encoding and retrieval while preliminary results from a follow-up investigation suggest similar results for face and location stimuli. In both studies, however, the critical requirement for VLPFC activity appears to be intention. That is, while passive (unintentional) encoding and retrieval produced reliable activity in the hippocampal formation bilaterally (Dove, Brett, Cusack, & Owen, submitted), even in individual participants, robust activation was only observed in VLPFC when participants were explicitly instructed either to encode or to retrieve.

Parallel studies suggest, however, that VLPFC functions extend beyond the domain of memory. For example, in one collaborative event-related fMRI study with Professor T. W. Robbins and colleagues in the Department of Experimental Psychology, Cambridge (Cools, Clark, Owen, & Robbins, 2002b), highly significant activity was observed in this region during a probabilistic reversal learning task which places minimal demands on memory; specifically during a critical last reversal error, at which point subjects stopped responding to a previously relevant pattern and reversed responding to a newly relevant pattern. Results such as these, in combination with the series of memory studies described above, illustrate the difficulty associated with developing a theory of frontal specialization which is sufficiently comprehensive to incorporate the main findings from ostensibly different types of cognitive task. On the basis of evidence accumulated thus far, it has been hypothesized that a general role for VLPFC is to map and implement arbitrary learned responses to specific stimuli for guiding behaviour (Owen, 2000).

A5.3 The role of the orbitofrontal cortex
Scientific direction: Owen (10%)
Other MRC posts: Rogers (6 months, 20%)
Grant-supported posts and visitors: Hinton, Arana

Data from human neuropsychology suggest that the functions of orbitofrontal cortex are quite distinct from those of lateral frontal regions, involving aspects of emotional and social decision making. For example, patients with damage to the orbitofrontal cortex exhibit marked impairments in laboratory based gambling or risk-taking tasks, suggesting that this part of the human frontal cortex contributes to complex decision making. In one series of PET studies the functions of the DLPFC and orbitofrontal cortices were compared explicitly, while in later studies the role of the orbitofrontal cortex in complex decision making was investigated. PET was used in both cases since the most ventral parts of the frontal lobe remain susceptible to acquisition artifacts when imaged using fMRI. In an initial study, a novel gambling task developed by Rogers (Rogers et al., 1999) was used. The task involved predicting which of two mutually exclusive outcomes would occur, but critically, the larger reward (and penalty) was associated with choice of the least likely outcome whereas the smallest reward (and penalty) was associated with choice of the most likely outcome. Resolving these "conflicting" decisions was associated with three distinct activation foci within the inferior and orbitofrontal prefrontal cortices. By contrast, increases in the degree of conflict inherent in these decisions was associated with only limited changes in the orbitofrontal cortex. These results suggest that decision making recruits multiple regions of the human inferior frontal cortex, receiving information from a diverse set of cortical and limbic inputs, and that the contribution of orbitofrontal regions may involve processing changes in reward-related information (Rogers, 1999). By adapting this same task to include a working memory component, this project has been extended through a further PET investigation and, more recently, an event-related fMRI study, to test whether the DLPFC and orbitofrontal cortices can be shown to be disproportionately involved in mnemonic processing and decision making, respectively (Rogers et al., in preparation). While the results partially confirm this hypothesis, they also demonstrate that such functional distinctions, even between anatomically and cytoarchitectonically distinct frontal regions, are far from absolute.
In a related series of investigations using PET, the relationship between the orbitofrontal cortex and the limbic system in aspects of motivation and reward has been investigated using primary reward (food) as an experimental variable. Motivation impacts on all forms of cognition and behaviour and can mediate both the vigour and direction of responses. The orbitofrontal cortex, which has direct neuronal connections with various limbic structures, including the amygdala, is well placed to code information about the motivational or reward value of incoming information. Psychologically, one can distinguish between motivational mechanisms that subserve homeostatic regulation (sometimes referred to as drive) from processes that identify highly attractive goals in the outside world (a process of incentive learning) which subsequently guide our actions. With respect to food motivation, previous imaging studies have identified hunger-related brain activity in imaging studies, but none, as yet, have specifically studied incentive processes. In one collaborative PET study with Drs A. Roberts, J. Parkinson and colleagues of the Department of Anatomy, Cambridge and Professor T. Holland and colleagues of the Department of Psychiatry, Cambridge, the effect of varying the incentive value of food stimuli was investigated in healthy volunteers along with the effect of having to make an affective decision relating to these stimuli. This was achieved through the presentation of restaurant menus which were tailored to individuals' food preferences and varied along two dimensions; incentive (high incentive or 'liked' foods versus low incentive or 'no particular preference' foods) and decision making (decision 'which would you prefer to eat' versus no decision 'consider each of these menu possibilities'). As predicted, varying the incentive value of the food stimuli activated the amygdala, but importantly, had no effect on the orbitofrontal cortex. In contrast, decision making activated the orbitofrontal prefrontal cortex, and in particular, affectively laden decisions (interaction between incentive value and decision making) produced significantly increased activity in this area.

A5.4 Lateralization of function within the prefrontal cortex
Scientific direction: Owen (10%)
Students: Lee

The issue of lateralization of function within the frontal lobe has also received considerable and renewed attention in recent years, fuelled primarily by a plethora of functional neuroimaging studies. While several of these studies have suggested that specific cognitive processes such as episodic memory encoding and retrieval may be strongly lateralized within the frontal lobe, an extensive review of the relevant imaging literature failed to provide convincing support for this functional asymmetry model (Lee, Robbins, & Owen, in press-a). Instead, we have suggested (Lee et al., 2000; Owen, Milner, Petrides, & Evans, 1996d) that episodic memory encoding and retrieval may actually involve similar regions of the lateral prefrontal cortex when all factors relating to the type of stimulus material (e.g. modality) are appropriately controlled, a position that concurs fully with results emerging from the parallel studies of working memory described above (e.g. Dove et al., submitted). To test this hypothesis directly a series of PET and fMRI studies has been conducted in collaboration with Professor T. W. Robbins and colleagues in the Department of Experimental Psychology, Cambridge and Professor P. Mathews and colleagues at the MRC Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB), Oxford. In one PET study (Lee, Robbins, Pickard, & Owen, 2000), easily verbalisable material lead to activation predominantly in the left lateral frontal cortex whilst non-easily verbalisable material lead to activation predominantly in the right lateral frontal cortex, in both cases irrespective of encoding and retrieval processes. In order to replicate and extend these findings, the same task was modified for use with fMRI (Lee et al., in press-b). It was found that, in comparison to a baseline condition, the encoding of visual stimuli led to a bilateral activation of the prefrontal cortex whilst the encoding of verbal stimuli led to a preferential activation of the left prefrontal cortex. An effect of stimulus type was less evident during retrieval with both visual and verbal stimuli leading to bilateral prefrontal cortex activation. Overall, encoding and retrieval activated similar regions of the prefrontal cortex. To extend these findings further, the tasks used in the fMRI study were used to assess a group of patients with unilateral frontal lesions and a group of healthy controls. The patients were significantly impaired compared to the healthy volunteers, although no significant differences were found in performance between the right- and left-sided lesioned patients. This result suggests that memory-related asymmetries sometimes observed during functional neuroimaging studies may not be critical for task performance.

A5.5 Frontostriatal interactions
Scientific direction: Owen (10%)
Other MRC posts: Dove (20%)

Our studies in patients with Parkinson's disease (PD) have revealed a progressive pattern of neuropsychological impairment, which, in its earliest stages, resembles that seen after damage to the frontal lobes (e.g. Cools, Stefanova, Barker, Robbins, & Owen, 2002a, Cox; Stefanova, Johnsrude, Robbins, & Owen, 2002; Dagher, Owen, & Brooks; 1999; Dagher, Owen, Boecker, & Brooks, 2001; Hodgson, Tiesman, Owen, & Kennard, 2002; Owen, 1997c; Owen, Iddon, Hodges, & Robbins; 1997; Owen, Doyon, Dagher, & Evans, 1998a; Owen, Doyon, Dagher, & Evans, 1999a; Owen, Sahakian, & Robbins, 1998c; Owen & Doyon, 1999). However, since PD is associated with both striatal and prefrontal dopamine loss, it is unclear whether these 'frontal-like' cognitive deficits result from one, or both, of these forms of pathology. This issue has implications both for the clinical management of PD patients and for our understanding of the functional relationship between frontal cortex and basal ganglia. In one study, PET was used to examine how regional blood flow in the frontal cortex and in the basal ganglia may be affected in patients with PD, during tests of planning and working memory (Owen et al., 1998a; 1999a; Cools et al., 2002a). Though patients showed no significant impairments in prefrontal cortex, differences were consistently observed in one subcortical area centred on the right internal segment of the globus pallidus (Gpi). This region constitutes the main basal ganglia outflow nucleus by which descending cortico-striatal inputs project back to discrete frontal regions. The results suggest that "frontal" cognitive deficits seen in early PD are in part the result of abnormal processing of prefrontal input through malfunctioning basal ganglia circuitry.

In a collaborative follow-up study with Drs R. Barker and S. Lewis of the MRC Centre for Brain Repair, Cambridge and Professor T. W. Robbins and colleagues from the Department of Experimental Psychology, Cambridge, fMRI was used to examine this issue further and to attempt to identify functional neuroanatomical 'markers' of executive dysfunction in PD patients. A sub-group of patients with executive deficits were shown to be impaired at manipulation, but not retrieval, within verbal working memory compared to a group of patients with no predefined executive impairments (Lewis et al., in press). Examined with fMRI, those patients with executive deficits showed reduced working memory activation in specific striatal, and this time also frontal-lobe, sites. No such changes occurred in patients who were not cognitively impaired. These results demonstrate, for the first time, that cognitive deficits in PD are accompanied by neural changes that are related to, but distinct from, those changes which underlie motoric deficits in these patients and that fMRI may provide a valuable tool for identifying those patients who may benefit maximally from targeted therapeutic strategies ( Lewis, Dove, Robbins, Barker, & Owen, submitted).

A5.6 The frontal lobes: pharmacological mechanisms
Scientific direction: Owen (10%)

Local injection and iontophoretic application of specific dopaminergic agents as well as electrophysiological measures in the monkey suggests that the dorsolateral frontal cortex is the critical locus for dopaminergic effects on high-level cognitive functions, although little is known about these effects in humans. This issue has been investigated in collaborative imaging studies with Professor T. W. Robbins and colleagues in the Department of Experimental Psychology, Cambridge and Dr. B. J. Sahakian in the Department of Psychiatry, Cambridge (Mehta et al., 2000; Cools, Stefanova, Barker, Robbins, & Owen, 2002a), one using methylphenidate in healthy control volunteers and the other using L-dopa in patients with Parkinson's disease. In the first study, the changes in regional cerebral blood flow induced by methylphenidate during the performance of a spatial working memory task were investigated to define the neuroanatomical locus of the beneficial effect of the drug (Mehta et al., 2000). The results showed that the methylphenidate-induced improvements in working memory performance occur with task-related reductions in blood flow in the dorsolateral frontal cortex. This was, to our knowledge, the first demonstration of a localization of a drug-induced improvement in spatial working memory performance in humans. In a second study (Cools et al., 2002a), we used PET to examine the critical locus of the effect of dopaminergic medication on high-level cognitive functioning in Parkinson's disease by comparing their rCBF 'on' and 'off' L-dopa. L-dopa was shown to effectively normalize blood flow in the right dorsolateral prefrontal cortex during planning and spatial working memory and a significant correlation was found between L-dopa-induced, planning-related blood flow decreases in the right dorsolateral prefrontal cortex and L-dopa-induced changes in performance on the planning task. The results of these two investigations are consistent, yet surprising, in demonstrating that dopaminergic agents improve performance on tests of working memory (and planning) by reducing blood flow in the dorsolateral frontal cortex. On this basis we have hypothesized that the observed dopamine-related blood flow reductions reflect increased efficiency, in a manner described previously by Furey, Pietrini, & Haxby (2000) for acetylcholine.

A5.7 Spearman's
Scientific direction: Duncan (20%)
Other MRC posts: Parr (100%)

The broad disorganization of behaviour that can follow prefrontal lesions is reminiscent of a key concept from psychometrics - "general intelligence" or Spearman's g (Spearman, 1904). Conventional intelligence tests are important because of their broad prediction of success in many different cognitive domains. In the previous funding period, we proposed that tests of this sort in large part measure an aspect of prefrontal function. In the current period, this proposal has been followed up with functional neuroimaging, in patient studies and in studies of normal cognition.

Using PET (Duncan et al., 2000), we tested two classical hypotheses concerning conventional intelligence tests. One, following Spearman (1904), is that these tests measure some specific but generally important aspect of cognitive function. This predicts focal brain activation; we predicted in particular focal activity in prefrontal cortex. The alternative, following Thomson (1951) and many others, is that intelligence tests measure an "average" of the brain's major cognitive functions, predicting diffuse activation in systems related to language, spatial processing, memory, knowledge and so on. The results were clearly in line with the Spearman hypothesis, showing focal activation in both DLPFC and VLPFC, with additional less consistent foci in premotor and inferior parietal cortex.

Patient studies have made use of the Cambridge Cognitive Neuroscience Research Panel, now including >25 patients with focal frontal lesions mapped by MRI, and a similar number of posterior controls. Using the methods of Brett et al. (2001) (see Project MR2.3), lesions are traced in standard atlas coordinates, allowing direct cross-reference to functional imaging results. The results suggest that familiar neuropsychological tests (Wisconsin card-sorting, verbal fluency) differentiate frontal and posterior lesions only by virtue of their shared variance with a standard test of fluid intelligence. We are also beginning to understand variability of cognitive impairment among prefrontal patients; orbitofrontal lesions, in particular, produce little or no fluid intelligence impairment. As patient numbers increase, we plan to address finer distinctions within prefrontal cortex (see following section A5.8).

In studies of normal function, we seek a cognitive interpretation of g. A characteristic of some frontal patients is goal neglect, or disregard of some task requirement though it can be understood and recalled. As described in the previous funding period (Duncan, Emslie, Williams, Johnson, & Freer, 1996), goal neglect can also be seen in the normal population, where it is strongly related to Spearman's g. In our tasks, explicit prompting always causes this neglect to resolve. We have now repeatedly confirmed the close association of goal neglect and Spearman's g. This association is identical in normal participants, frontal-lobe and posterior patients. Goal neglect is insensitive to concurrent task demands, requirements for sustained attention, and recency of task switches. Indeed, preliminary data suggest that immediate, concurrent task demands can conceal the relationship between error and g. Instead, the important consideration may be the overall complexity of task rules.
Though this is ongoing work, our hypothesis is that specific regions of prefrontal cortex play a role in constructing an on-line model of current task events, including relevant inputs, outputs, facts and rules from semantic memory etc. The adequacy of this process is largely reflected in Spearman's g. In goal neglect, task components compete for representation; components can be lost from the active model though still available for explicit recall.

A5.8 The adaptive coding model
Scientific direction: Duncan (10%)
Other MRC posts: Owen (5%)

Very recently, we have proposed a new perspective on prefrontal function (Duncan, 2001; Duncan & Miller, 2002). In over 20 years of animal (Goldman-Rakic, 1988) and imaging (Cabeza & Nyberg, 2000) studies, a dominant theme has been that particular regions of prefrontal cortex should be strongly specialized for particular cognitive functions. In our adaptive coding model, the emphasis instead is on flexibility or plasticity of neural function.

In a systematic literature review (Duncan & Owen, 2000a, b), we synthesized data from all published studies dealing with 5 different types of cognitive demand - inhibition of prepotent responses, task novelty, working memory load, working memory delay, and perceptual difficulty. In one respect, activations within prefrontal cortex showed clear structure, with strong clustering of activations in and around the inferior frontal sulcus (including the DLPFC region described above), along the frontal operculum towards the anterior insula (the VLPFC region above), and in the dorsal anterior cingulate. For the remainder of prefrontal cortex - including most of the medial and all of the orbital surfaces - there was little or no evidence of demand-related activity. As regards cognitive domain, however, there was no evidence for regional specialization. Activation patterns associated with all five demands were closely similar (Figure A5.2).

In the adaptive coding model (Duncan, 2001a; Duncan & Miller, 2002), we propose that individual frontal neurons must be highly plastic in the information they code. Neural properties adapt to the current task context, producing a dense, distributed representation of relevant task information and events. This model casts light on the roles of frontal cortex in working memory, attention and control. As regards working memory, prefrontal cortex produces a representation of just that information of relevance to a current task (see A5.7 above). As regards attention, prefrontal cortex filters out information of no current importance. As regards control, we propose that selective prefrontal representation of task-relevant information produced the "bias" signal (see Project A1) driving related coding in posterior and subcortical systems.

To some extent at least, flexibility is the converse of specialization. At least for much of the lateral surface, we suggest that regional specialization is statistical rather than absolute (Duncan, 2001a; Duncan & Miller, 2002), reflecting different but overlapping regional distributions of potentially relevant cells for different aspects of task representation. This proposal is consistent with the hints of regional specialization in our imaging studies, coupled with difficulty in establishing strong double dissociations. Direct tests are planned in the next funding period.

Project A6: Monitoring, arousal and sustained attention.

Investigations into the methodologically difficult area of executive, higher-level control processes have increased dramatically in the last decade or so - not least reflecting the importance of dysfunctions of this type in determining clinical outcome following brain injury. Aspects of a dysexecutive syndrome (a term coined by Baddeley and Wilson at the Unit in 1988) are common following traumatic brain injury (TBI - affecting approximately 35 per 100,000 of the population, predominantly young men), along with other causes of brain damage, and are increasingly being implicated in a number of developmental conditions including attention deficit hyperactivity disorder (ADHD).

Figure A5.2 Prefrontal activations from studies of response conflict (green), task novelty (purple), number of elements in working memory (yellow), working memory delay (red) and perceptual difficulty (blue). On the lateral surface, there are activation clusters around the inferior frontal sulcus (IFC) and frontal operculum/insula (here projected onto lateral surface, just anterior to Sylvian fissure SF). On the medial surface, activations are largely restricted to the dorsal anterior cingulate (above corpus callosum CC). Even for dorsolateral surface there are large areas without activations (dorsal brain view); only occasional activations are seen on orbital surface (ventral view).

Any factor that limits the goal-directed expression of other abilities in everyday life should be a high priority for rehabilitation. To date, relatively few systematic attempts to remediate dysexecutive disorders have been reported. As the very functions that may facilitate functional recovery in other capacities (error detection, flexible adaptation, development of compensatory strategies and so forth) are those that are compromised, this is an inherently challenging task. There are two principal aims within Project A6. The first is to make strong links between basic experimental/functional imaging and theoretical development in this area and the development and assessment of useful rehabilitative techniques. The second is to use results of rehabilitation studies to further constrain and develop theory. Dissemination of research findings to clinical colleagues, including scientific reviews of the theoretical and empirical basis of rehabilitation, has continued throughout this funding period (Manly, in press; Manly & Robertson, 1997; Manly & Robertson, in press; Manly et al., 2002b; Robertson, 1998b; Robertson, 1999a; Robertson, 1999b; Robertson, 1999c; Robertson, 1999d; Robertson, 2000; Robertson & Murre, 1999)

A6.1 Sustained attention/Goal monitoring
Scientific direction: Robertson (2 years, 20%), Manly (30%)
Other MRC posts: Cusack (5%), Evans (5%)
Grant-supported posts and visitors: Rorden, Datta

A key function in achieving goals is the capacity to keep a goal/plan actively in mind and to maintain a particular processing stance - even in the absence of strong or continuous environmental triggers for that state. The Sustained Attention to Response Test (SART: (Robertson, Manly, Andrade, Baddeley, & Yiend, 1997a) was designed to form a simple and tractable model of such situations. In the task, participants are asked to watch a succession of single digits appearing on a computer monitor at a regular pacing of approximately 1 digit per second. The aim is simply to press a single response key as each digit appears with the exception of a nominated no-go digit, to which no response should be made. As the no-go trial appears infrequently within the random sequence of digits, it was hypothesized that participants would tend to neglect this goal, and instead lapse into a rather absentminded repetitive response mode. Not only are errors common within the normal population, but the frequency of those errors is significantly related to individual propensity to absentminded slips in everyday life, as assessed using standardised self- and informant-report questionnaires (Manly, Robertson, Galloway, & Hawkins, 1999). This relationship between a controlled and reliable computer task and lapses in complex everyday situations is also present in the TBI population (Robertson et al., 1997a). Investigations on the predictive relationship of the SART to other neuropsychological and everyday functioning measures in the brain injured population are continuing with Evans and colleagues at the Oliver Zangwill Centre.

The SART lends itself to experimental manipulation. Recent work has demonstrated a) that the key demands of the task lie in the duration of the intervals between no-go target presentations (Manly et al., 1999); and b) that accounts of individual differences in performance couched purely in terms of speed-accuracy trade-off are not adequate (Manly, Davison, Heutink, Galloway, & Robertson, 2000b). Perhaps the most compelling demonstration that performance on the SART depends upon the maintenance of active top-down control (in addition to - or in order to exert - any response inhibition capacity) comes from the results of cueing studies. Across three studies, patients and healthy controls were exposed to occasional and randomly timed auditory tones as they performed the test. They were asked to use the tone as a cue to think about what they were doing. Although participants, if asked, have invariably been able to remember what they should be doing during the task, these spaced reminders nevertheless act to significantly improve performance. This suggests that exogenous cueing - or perhaps crucially, interruption to current activity - can allow participants to better maintain a link between a remembered goal and their subsequent actions (Manly et al., submitted-a).

A difficulty in study of brain injury is the possibility of damage to multiple systems separately affecting task performance. One alternative approach is to examine within-subject modulation of normal performance. Previous research suggests that activities performed late at night, early in the morning, or by sleep-deprived people are more vulnerable to absentminded slips and can be strikingly similar to the performance of dysexecutive patients. Neurophysiological studies further suggest that sleep onset and offset is not expressed as a uniform effect across the brain, but one that disproportionately de-activates particular regions, including frontal cortex. Repeated assessment of young healthy subjects over four days showed that the capacity to withhold responses in the SART - and by inference to actively maintain a simple goal in mind - indeed showed clear circadian variation. As might be predicted on the basis of automatic/controlled processing distinctions and their relationship to prefrontal function, the more routine, overlearned aspects of the task were wholly unaffected (Manly et al., 2001b).

Taking advantage of the tight temporal resolution of event related potentials (ERPs), we examined whether electrophysiological signals could be used to predict subsequent success or failure on a no-go trial, thereby forming a marker of attentional allocation. The results showed that the P300 component (often attributed to attentional processing) was reduced in trials that preceded an action slip (Datta et al., submitted; Manly et al., 2000a). Initial analysis of data collected in collaboration with colleagues at the Rotman Institute in Toronto further suggests that the P300 is relatively suppressed in TBI patients - who are prone to high error rates - as they perform the task (Armilio, Picton, Robertson, & Stuss, 1999).

Work comparing TBI patients with healthy controls suggests, perhaps counterintuitively, that a fixed sequence version of the SART (e.g., requiring a response to be withheld to the number 9 in the repeating sequence 1 2 3 4 5 6 7 8 9 1 2 3 …) is actually more sensitive to the patients' impairments than the more challenging conventional random sequence. We have therefore suggested that the low demands of this ostensibly trivial task - together with the long intervals between no-go trials - may exacerbate the patients' difficulty in maintaining a sufficiently alert and goal-focused state. Comparison of regional cerebral activation associated with the two conditions supports this view. In a PET study, performance of the fixed sequence SART (which attracts errors even in healthy volunteers) was associated with significantly increased blood flow above the random sequence in regions previously limited to sustained attention - specifically within right dorsolateral prefrontal and parietal areas (Manly et al., 2001c; Manly et al., submitted-b).

Some patients with a dysexecutive syndrome show a clear dissociation between stated intention and subsequent action. As demonstrated by Duncan and colleagues (Project A5) milder forms of such goal neglect can be observed within many of the brain injured and - to a lesser degree - in the normal population. Building on the experimental work described above, with Evans and colleagues at the Oliver Zangwill Centre, we sought to examine the effect of environmental cues/interruption of current activity on patients' performance in a task that seeks to replicate some of the complexities of everyday life (where the impact of dysexecutive deficits are most apparent). In a variant of Shallice and Burgess's (1991) Six Elements test, we asked head-injured patients to try to perform at least some of each of five different activities within a fifteen-minute period. As finishing each component task would take longer than the total time available, the test placed emphasis on patients' ability to keep in mind the main goal (to do at least some of each task) and to switch flexibly between tasks at suitable points. In line with previous findings, and despite clear comprehension and memory for the instructions, the performance of dysexecutive patients deviated sharply from that of IQ matched controls - the key error being to get caught up in one particular task to the detriment of the main goal. The use of a randomly timed tone to periodically interrupt ongoing performance not only significantly improved the patients' performance, but rendered it indistinguishable from that of the healthy control group (Manly et al., 2001a). Such results have value in assessment (for example, in ruling out the impact of poor memory as a cause for impaired performance) and suggest that appropriate environmental cueing could minimise the handicap associated with these deficits in everyday situations. The use of technologies (such as palm-top computers or vibrating watches) to perform this cueing function in everyday life is an area that we are actively exploring in collaboration with the Oliver Zangwill Centre.

Developments in the investigation of control functions have largely been conducted in Western countries and with English Speaking populations. With Chan, we examined the applicability of widely used clinical measures (Six Elements Task, Tower of Hanoi) and informant/self report checklists of dysexecutive behaviours (Broadbent's Cognitive Failures Questionnaire, the DEX dysexecutive questionnaire) within healthy and head-injured Cantonese speaking Hong Kong residents. The results suggest that the overall levels of performance and discrepancies between head injured and healthy participants, and the relationships between the tasks and checklist ratings, are robust across this cultural difference (Chan & Manly, 2002).

A6.2 Attention and higher level control in children
Scientific direction: Robertson (5%, 2 years), Manly (30%)
Students: Dobler

Vast and increasing numbers of children are referred to clinical services with suspected attentional problems. In some studies, referral rates for ADHD have reached 6% of all school age boys and 1.5% of girls. Deficits in attention processes have been implicated in many other developmental conditions including autism and Tourette's syndrome, and following acquired brain damage in childhood. Despite the scale of the perceived difficulty, there has been somewhat of a dichotomy between approaches in attention within the adult and developmental literature. While for adults, neuroscientific analysis of functional and neuroanatomical separations in attention systems has fed through into improved assessment and targeted rehabilitation, diagnosis of childrens' attention deficits continues to rest almost exclusively on parental and teacher reports. As discussed in Project A2, the observation of unilateral neglect-like phenomena in children led us to adapt and collect normative data on a range of targeted performance-based attention measures. Among the measures now incorporated into the Test of Everyday Attention for Children (Manly et al., 2002a) were variants of the SART and the simple tone counting measure of sustained attention first developed by Wilkins and colleagues at the Unit. To date, we have applied this differential assessment approach to children diagnosed with ADHD and acquired brain injury (Anderson, Fenwick, Manly, & Robertson, 1998; Micallef, Anderson, Anderson, Robertson, & Manly, 2001). Disproportionate deficits in maintaining a simple goal/sustained attention were a prevalent feature in the ADHD group. Current collaborative projects include work (with K. Cornish, McGill University) on relationships between cognitive/behavioural dysfunction (assessed using the TEA-Ch), spatial bias and candidate genetic markers.

A6.3 Persistent vegetative state
Scientific direction: Owen (5%)

Despite converging agreement about the definition of persistent vegetative state, recent reports have raised concerns about the accuracy of diagnosis in some patients, and the extent to which, in a selection of cases, residual cognitive functions may remain undetected. Objective assessment of residual cognitive function can be extremely difficult since motor responses may be minimal, inconsistent, and difficult to document. In the absence of motor output, functional neuroimaging with well-documented paradigms may allow the imaging of specific task-related cortical activation, and provide one means of assessing cognitive processing. Owen, working with the clinical team at the WBIC and Professor D. Menon of Department of Anaesthesia, Cambridge, has investigated strategies for using PET in this role, the clinical condition of many patients precluding MRI. Functional neuroimaging in two persistent vegetative cases has produced extremely encouraging results, leading to publications in The Lancet (Menon et al., 1997), Trends in Neurosciences (Menon et al., 1999) and Neurocase (Owen et al., in press), as well as significant media coverage on television, radio and in print. In these two patients, clear and predicted regional cerebral blood flow responses were observed during well-documented activation paradigms (face recognition; see Figure A6.1, and speech perception) which have been shown to produce specific, robust and reproducible activation patterns in normal volunteers. Some months after scanning, both patients made a significant recovery suggesting that imaging in this patient group may provide novel information about likely outcome. In spite of the multiple logistic and procedural problems involved, these results have major clinical and scientific implications and provide a strong basis for the systematic study of possible residual cognitive function in these patients.

A6.1: Surface rendered normalised PET data from the familiar face perception task superimposed on standard 3D-rendered magnetic resonance template. Both for control and patient, strong right hemisphere activation is seen in the fusiform gyrus.

AWARDS AND HONOURS

In 1998, Dr R. P. Carlyon was was elected a Fellow of the Acoustical Society of America. His article co-authored with D. M. Bishop, J. Deeks, and S. Bishop (see publication list) won the Journal of Speech, Language, and Hearing Research's Editors' Award for 1999. Dr J. Duncan was made an Honorary Professor at the University of Wales in 2000, was invited with six others to form the Scientific Advisory Board of MIT's McGovern Institute in 2002, and became Secretary of the International Association for the Study of Attention and Performance in 2002. In 2000 he gave the British Psychological Society's Broadbent Lecture. From 1995 to 2000, Dr A. M. Owen was Vice-President of the International Society For Behavioural Neuroscience. Dr I. H. Robertson was made Visiting Professor at University College London in 1997.

PUBLICATIONS

Refereed Journals

Anderson, V., Fenwick, T., MANLY, T., & ROBERTSON, I. H. (1998). Attentional skills following traumatic brain injury. Brain Injury, 12, 937-949.
ARNELL, K., & DUNCAN, J. (2002). Separate and shared sources of dual-task cost in stimulus identification and response selection. Cognitive Psychology, 44, 105-147.
BADDELEY, A. D., EMSLIE, H., KOLODNY, J., & DUNCAN, J. (1998). Random generation and the executive control of working memory. Quarterly Journal of Experimental Psychology, 51A, 819-852.
Beschin, N., & ROBERTSON, I. H. (1997). Personal versus extrapersonal neglect: a group study of their dissociation using a reliable clinical test. Cortex, 33, 379-384.
BISHOP, D. V. M., CARLYON, R. P., DEEKS, J. M., & BISHOP, S. J. (1999). Auditory temporal processing impairment: neither necessary nor sufficient for causing language impairment in children. Journal of Speech, Language, and Hearing Research, 42, 1295-1310.
BONFIGLIOLI, C., DUNCAN, J., RORDEN, C., & Kennett, S. (2002). Action and perception: Evidence against converging selection processes. Visual Cognition, 9, 458-476.
BOR, D., DUNCAN, J., & OWEN, A. M. (2001). The role of spatial configuration in tests of working memory explored with functional neuroimaging. Scandinavian Journal of Psychology, 42, 217-224.
BOR. D., DUNCAN, J., & OWEN, A. M. (in press). Encoding strategies dissociates prefrontal activity from working memory demand. Neuron.
BOR, D., DUNCAN, J., & OWEN, A. M. (submitted). Lateral prefrontal activity depends on the configuration of stimuli in spatial working memory.
BRETT, M., JOHNSRUDE, I. S., & OWEN, A. M. (2002). The problem of functional localization in the human brain. Nature Reviews Neuroscience, 3, 243-249.
CALDER. A. J., LAWRENCE, A., KEANE, J., SCOTT, S., OWEN, A. M., Christoffels, I., & YOUNG, A. W. (in press). Reading the mind from eye gaze. Neuropsychologia.
CARLYON, R. P. (1997). The effects of two temporal cues on pitch judgements. Journal of the Acoustical Society of America, 102, 1097-1105.
CARLYON, R. P. (1998). Comments on A unitary model of pitch perception [Journal of the Acoustical Society of America 102, 1811-1820. (1997)]. Journal of the Acoustical Society of America, 104, 1118-1121(Letter )
CARLYON, R. P. (2000). Detecting coherent and incoherent frequency modulation. Hearing Research, 140,173-188.
CARLYON, R. P., CUSACK, R., Foxton, J. M., Aikman, G. A., & ROBERTSON, I. H. (2000a). Effects of attention on auditory stream segregation. British Journal of Audiology, 34, 112-113.
CARLYON, R. P., CUSACK, R., Foxton, J. M., & ROBERTSON, I. H. (2001a). Effects of attention and unilateral neglect on auditory stream segregation. Journal of Experimental Psychology: Human Perception and Performance, 27, 115-127.
CARLYON, R. P., CUSACK, R., & ROBERTSON, I. H. (2001b). Effects of attention and unilateral neglect on auditory stream segregation. Journal of Experimental Psychology, 27, 115-127.
CARLYON, R. P., & DATTA, A. J. (1997). Excitation produced by Schroeder-phase complexes: evidence for fast-acting compression in the auditory system. Journal of the Acoustical Society of America, 101, 3636-3647.
CARLYON, R. P., & DEEKS, J. M. (in press). Limitations on rate discrimination. Journal of the Acoustical Society of America.
CARLYON, R. P., DEEKS, J. M., NORRIS, D., & BUTTERFIELD, S. (2002a). The Continuity Illusion and Vowel Identification. Acta Acustica united with Acustica, 88, 408-415
CARLYON, R. P., Demany, L., & DEEKS, J. M. (2001c). Temporal pitch perception and the binaural system. Journal of the Acoustical Society of America, 109, 686-700.
CARLYON, R. P., Geurts, L., & WOUTERS, J. (2000b). Detection of small across-channel timing differences by cochlear implantees. Hearing Research, 141, 141-154.
CARLYON, R. P., Moore, B. C. J. & MICHEYL, C. (2000c). The effect of modulation rate on the detection of frequency modulation and mistuning of complex tones. Journal of the Acoustical Society of America, 108, 304-315.
CARLYON, R. P., & Shamma, S. (submitted). An account of monaural phase sensitivity.
CARLYON, R. P., van Wieringen, A., LONG, C. J., DEEKS, J. M., & J. WOUTERS (2002b). Temporal pitch mechanisms in acoustic and electric hearing. Journal of the Acoustical Society of America, 112, 621-633.
Chan, R. C. K., & MANLY, T. (2002). The application of 'dysexecutive syndrome' measures across cultures: Performance and checklist assessment in neurologically healthy and traumatically brain-injured Hong Kong Chinese volunteers. Journal of the International Neuropsychological Society, 8, 771-780.
Chelazzi, L., DUNCAN, J., Miller, E. K., & Desimone, R. (1998). Responses of neurons in inferior temporal cortex during memory-guided visual search. Journal of Neurophysiology, 80, 2918-2940.
Chelazzi, L., Miller, E. K., DUNCAN, J., & Desimone, R. (2001). Responses of neurons in macaque area V4 during memory-guided visual search. Cerebral Cortex, 11, 761-772.
Cools, R., Clark, L., OWEN, A. M., & Robbins, T. W. (2002a). Defining the neural mechanisms of probabilistic reversal learning using event-related functional magnetic resonance imaging. Journal of Neuroscience, 22, 4563-4567.
Cools, R., Stefanova, E., Barker, R. A., Robbins, T. W., & OWEN, A. M. (2002b). Dopaminergic modulation of high-level cognition in Parkinson's disease: the role of the prefrontal cortex revealed by PET. Brain, 125, 584-594.
COX, S. M. L., Stefanova, E., JOHNSRUDE, I. S., Robbins, T. W., & OWEN, A. M. (2002). Preference formation and working memory in Parkinson's disease and normal ageing. Neuropsychologia, 40, 317-326.
CUSACK, R., & CARLYON, R. P. (in press). Perceptual asymmetries in audition. Journal of Experimental Psychology: Human Perception and Performance.
CUSACK, R., CARLYON, R. P., & ROBERTSON, I. H. (2000). Neglect between but not within auditory objects. Journal of Cognitive Neuroscience, 12, 1056-1065.
CUSACK, R., CARLYON, R. P., & ROBERTSON, I. H. (2001). Auditory midline and spatial discrimination in patients with unilateral neglect. Cortex, 37, 706-709.
CUSACK, R., DEEKS, J., Aikman, G., & CARLYON, R. P. (submitted). Effects of location, frequency region, and time course of selective attention on auditory scene analysis.
Dagher, A., OWEN, A. M., Boecker, H., & Brooks, D. J. (2001). The role of the striatum and hippocampus in motor planning: a PET activation study in Parkinson's disease. Brain, 124,1020-1032.
Dagher, A., OWEN, A. M., & Brooks, D. J. (1999). Mapping the network for planning: a correlational PET activational study with the Tower of London task. Brain, 122, 1973-1987.
DATTA, A., HAWKINS, K., HEUTINK, J., MANLY, T., CUSACK, R., RORDEN, C., & ROBERTSON, I. H. (submitted). An electrophysiological predictor of imminent human error.
Desimone, R., & DUNCAN, J. (1995). Neural mechanisms of selective visual attention. Annual Review of Neuroscience, 18, 193-222.
DOBLER, V. B., MANLY, T., Anker, S., ROBERTSON, I. H., & Atkinson, J. (submitted). Poor sustained attention and subtle 'neglect' of left space: A demonstration in a normal sample.
DOBLER, V., MANLY, T., Atkinson, J., WILSON, B. A., Ioannou, K., & ROBERTSON, I. H. (2001). Interaction of hand use and spatial selective attention in children. Neuropsychologia, 39, 1055-1064.
DOBLER, V. B., MANLY, T., Verity, C., Woolrych, J., & ROBERTSON, I. H. (submitted). Modulation of Spatial Attention in a Child with Developmental Unilateral Neglect. .
Doyon, J., OWEN, A. M. Jackson, P. L., Lafleur, M., Cesaro, P., & Remy, P. (in press). Analysis des effets therapeutiques au plan moteur et cognitif des greffes de cellules mesencephaliques dopaminergiques chez les patients attients de la maladie de parkinson. Medecine/Sciences.
DOVE, A., BRETT, M., CUSACK, R., & OWEN, A. M. (submitted). Hippocampal system and prefrontal memory functions: The role of intention.
DUNCAN, J. (1998). Converging levels of analysis in the cognitive neuroscience of visual attention. Philosophical Transactions of the Royal Society B, 353, 1307-1317.
DUNCAN, J. (2001a). An adaptive coding model of neural function in prefrontal cortex. Nature Reviews Neuroscience, 2, 820-829.
DUNCAN, J., Bundesen, C., Olson, A., Humphreys, G., Chavda, S., & Shibuya, H. (1999). Systematic analysis of deficits in visual attention. Journal of Experimental Psychology: General, 128, 450-478.
DUNCAN, J., Bundesen, C., Olson, A., Humphreys, G., WARD, R., Kyllingsbæk, S., van Raamsdonk, M., RORDEN, C., & Chavda S. (submitted). Attentional functions in dorsal and ventral simultanagnosia.
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DUNCAN, J., Humphreys, G. W., & WARD, R. (1997a). Competitive brain activity in visual attention. Current Opinion in Neurobiology, 7, 255-261.
DUNCAN, J., MARTENS, S., & WARD, R. (1997b). Restricted attentional capacity within but not between sensory modalities. Nature, 387, 808-810.
DUNCAN, J., & OWEN, A. M. (2000a). Common regions of the human frontal lobe recruited by diverse cognitive demands. Trends in Neurosciences, 23, 475-483.
DUNCAN, J., Seitz, R. J., KOLODNY, J., BOR, D., Herzog, H., AHMED, A., NEWELL, F. N., & EMSLIE, H. (2000). A neural basis for general intelligence. Science, 289, 457-460.
DUNCAN, J., WARD, R., & SHAPIRO, K. (1994). Direct measurement of attentional dwell time in human vision. Nature, 369, 313-315.
ELVEVÅG, B., DUNCAN, J., & McKenna, P. J. (2000). The use of cognitive context in schizophrenia: An investigation. Psychological Medicine, 30, 885-897.
EPSTEIN, R. (2000a). The neural-cognitive basis of the Jamesian stream of thought. Consciousness & Cognition, 9, 550-575.
EPSTEIN, R. (2000b). Substantive thoughts about substantive thoughts: A reply to Galin. Consciousness & Cognition, 9, 584-590.
EPSTEIN, R., DeYoe, E. A., Press, D. Z., Rosen, A. C., & Kanwisher, N. (2001). Neuropsychological evidence for a topographical learning mechanism in parahippocampal cortex. Cognitive Neuropsychology, 18, 481-508.
EPSTEIN, R., GRAHAM, K. S., & Downing, P. E. (submitted). Scene representations in human parahippocampal cortex are viewpoint-dependent.
EVERLING, S., TINSLEY, C. J., Gaffan, D., & DUNCAN, J. (2002). Filtering of neural signals by focused attention in the monkey prefrontal cortex. Nature Neuroscience, 5, 671-676.
FARRELL, M., & ROBERTSON, I. H. (1998). Mental rotation and the automatic updating of body-centred spatial relationships. Journal of Experimental Psychology: Learning, Memory and Cognition, 24, 227-233.
FARRELL, M., & ROBERTSON, I. H. (2000). Automatic updating of egocentric spatial relationships: Impairment due to right posterior lesions. Neuropsychologia, 38, 585-595.
FARRELL, M. J., ROBERTSON, I. H., & Thomson, J. A. (in press). Awareness of spatial relationships during locomotion without vision. Proceedings of the International Society for Psychophysics.
Gallagher, S., & MARCEL, A. J. (1999). The self in contextualized action. Journal of Consciousness Studies, 6, 4-30.
GOCKEL, H., & CARLYON, R. P. (1998). Effects of ear of entry and perceived location of synchronous and asynchronous components on mistuning detection. Journal of the Acoustical Society of America, 104, 3534-3545
GOCKEL, H., & CARLYON, R. P. (2000). Frequency modulation detection interference produced by asynchronous and nonsimultaneous interferers. Journal of the Acoustical Society of America, 108, 2329-36.
GOCKEL, H., & CARLYON, R. P. (in press). Effect of modulator asynchrony for sinusoidal and noise modulators on frequency and amplitude modulation detection interference. Journal of the Acoustical Society of America.
GOCKEL, H., CARLYON, R. P., & MICHEYL, C. (1999). Context dependence of fundamental frequency discrimination: Lateralized temporal fringes. Journal of the Acoustical Society of America, 106, 3553-3563.
GOCKEL, H., Moore, B. C. J., & CARLYON, R. P. (2001). Influence of rate of change of frequency on the overall pitch of frequency modulated tones. Journal of the Acoustical Society of America, 109, 701-712.
Grimault, N., MICHEYL, C., CARLYON, R. P., Arthaud, P., & Collet, L. (2000). Influence of peripheral resolvability on the perceptual segregation of harmonic complex tones differing in fundamental frequency. Journal of the Acoustical Society of America, 108, 263-271.
Grimault, N., MICHEYL, C., CARLYON, R. P., Arthaud, P., & Collet, L. (2001). Perceptual auditory stream segregation of sequences of complex sounds in subjects with normal and impaired hearing. British Journal of Audiology, 35, 173-82.
Grimault, N., MICHEYL, C., CARLYON, R. P., & Collet, L. (2002). Evidence for two pitch encoding mechanisms using a selective auditory training paradigm. Perception and Psychophysics, 64, 189-197.
Ho, A. K., MANLY, T., Nestor, P. J., Sahakian, B. J., Robbins, T. W., Rosser, A. E., & Barker, R. A. (in press). A case of unilateral neglect in Huntington's Disease, Neurocase.
Hodgson, T. L., Bajwa, A., OWEN, A. M., & Kennard, C. (2000). The strategic control of gaze direction in the Tower of London Task. Journal of Cognitive Neuroscience, 12, 1-14.
Hodgson, T. L., Tiesman, B, OWEN, A. M., & Kennard, C. (2002). Abnormal gaze strategies during problem solving in Parkinson's disease. Neuropsychologia, 40, 411-422.
Hornak, J., DUNCAN, J., & Gaffan, D. (2002). The role of the vertical meridian in visual memory for objects. Neuropsychologia, 40, 1873-1880.
Humphreys, G. W., Romani, C., Olson, A., Riddoch, M. J., & DUNCAN, J. (1994). Non-spatial extinction following lesions of the parietal lobe in humans. Nature, 372, 357-359.
JOHNSRUDE, I. S., Giraud, A. L., Morosan, P., BRETT, M., OWEN, A. M., & Zilles, K. (2000a). Functional Imaging of the auditory system: The use of positron emission tomography. Proceedings of the 4th Annual Congress of Otorhinolaryngology Head and Neck Surgery, 35-42.
JOHNSRUDE, I. S., OWEN, A. M., Crane, J., Milner, B., & Evans, A. C. (1999a). A cognitive activation study of memory for spatial relationships. Neuropsychologia, 37, 829-841.
JOHNSRUDE, I. S., OWEN, A. M., White, N. M., Zhao, V. W., & Bohbot, V. (2000b). Impaired preference learning after anterior temporal-lobe resection in humans. Journal of Neuroscience, 20, 2649-2656.
JOHNSRUDE, I. S., OWEN, A. M., Zhao, V. W., & White, N. M. (1999b). Conditioned pattern preference without awareness in humans. Learning and Motivation, 30, 250-264.
LAMBIE, J. A., & MARCEL, A. J. (2002). Consciousness and emotion experience: A theoretical framework. Psychological Review, 109, 219-259.
LAVIE, N., & ROBERTSON, I. H. (2001). The role of perceptual load in neglect: Rejection of ipsilesional distractors is facilitated with higher central load. Journal of Cognitive Neuroscience, 13, 867-876.
LEE, A. C. H., GRAHAM, K. S., SIMONS, J., HODGES, J. R., OWEN, A. M., & PATTERSON, K. (2002b). Regional brain activations differ for semantic features but not categories. NeuroReport, 13, 1497-1501
LEE, A. C. H., Robbins, T. W., GRAHAM, K., & OWEN, A. M. (2002). Pray or Prey? Semantic memory investigated using positron emission tomography. Neuroimage, 16, 724-735.
LEE, A. C. H., Robbins, T. W., & OWEN, A. M. (in press-a). Episodic Memory and the Frontal Lobes: Functional Neuroimaging Studies of Encoding and Retrieval. Critical Reviews in Neurobiology.
LEE, A. C. H., Robbins, T. W., Pickard, J. D., & OWEN, A. M. (2000). Left or right prefrontal cortical involvement in episodic memory encoding and retrieval?: The effects of stimulus type. Neuropsychologia, 38, 677-692.
LEE, A. C. H., Robbins, T. W., Smith, S., Calvert, G., Tracey, I., Matthews, P., & OWEN, A. M. (in press-c). Evidence for asymmetric frontal lobe involvement in episodic memory from functional magnetic resonance imaging and patients with unilateral frontal lobe excisions. Neuropsychologia.
Levine, B., ROBERTSON, I., CLARE, L., Carter, G., Hong, J., WILSON, B. A., DUNCAN, J., & Stuss, D. T. (2000). Rehabilitation of executive functioning: An experimental-clinical validation of Goal Management Training. Journal of the International Neuropsychological Society, 6, 299-312.
Lewis, S. G. J., Cools, R., Robbins, T. W., DOVE, A., Barker, R. A., & OWEN, A. M. (in press). Heterogeneity in the executive deficit in Parkinson's disease: Specifying component processes. Neuropsychologia.
Lewis, S. G. J., DOVE, A., Robbins, T. W., Barker, R. A., & OWEN, A. M. (submitted). Cognitive impairments in early Parkinson's disease are accompanied by reductions in activity in fronto-striatal neural circuitry.
LYZENGA, J., & CARLYON, R. P. (1999). Center frequency modulation detection for harmonic complexes resembling vowel formants and its interference by off-frequency maskers. Journal of the Acoustical Society of America, 105, 2792-2806
LYZENGA, L., & CARLYON, R. P. (2000). Binaural effects in frequency modulation detection interference for vowel formants. Journal of the Acoustical Society of America, 108, 753-759.
MANLY, T. (2001). Developments in the rehabilitation of unilateral neglect. Advances in Clinical Neuroscience and Rehabilitation, 1, 18-19.
MANLY, T. (2002). Cognitive Rehabilitation for Unilateral Neglect. Neuropsychological Rehabilitation, 12, 289-310.
MANLY, T., Anderson, V., NIMMO-SMITH, I., Turner, A., WATSON, P. C., & ROBERTSON, I. H. (2002). The differential assessment of children's attention: The Test of Everyday Attention for Children (TEA-Ch), normative sample and ADHD performance. Child Psychology and Psychiatry, 42, 1065-1081.
MANLY, T., DAVISON, B., HEUTINK, J., GALLOWAY, M., & ROBERTSON, I. H. (2000). Not enough time or not enough attention?: Speed, error and self-maintained control in the Sustained Attention to Response Test (SART). Clinical Neuropsychological Assessment, 3, 167-177.
MANLY, T., HAWKINS, K., EVANS, J. J., WOLDT, K., & ROBERTSON, I. H. (2002a). Rehabilitation of Executive Function: Facilitation of effective goal management on complex tasks using periodic auditory alerts. Neuropsychologia, 403, 271-281.
MANLY, T., HEUTINK, J., DAVIDSON, B., GAYNORD, B., GREENFIELD, E., PARR, A., RIDGEWAY, V., & ROBERTSON, I. H. (submitted-a). An electronic knot in the handkerchief: 'Content free cueing' and the maintenance of attentive control.
MANLY, T., Lewis, G. H., ROBERTSON, I. H., WATSON, P. C., & DATTA, A. K. (2001). Coffee in the cornflakes: Time-of-day, routine response control and subjective sleepiness. Neuropsychologia, 40, 747-758.
MANLY, T., OWEN, A. M., McAvinue, L., DATTA, A., Lewis, G. H., RORDEN, C., Pickard, J., & ROBERTSON, I. H. (submitted-b). Enhancing the sensitivity of a sustained attention task to frontal damage. Convergent clinical and functional imaging evidence.
MANLY, T., ROBERTSON, I. H., GALLOWAY, M., & HAWKINS, K. (1999). The absent mind: Further investigations of sustained attention to response. Neuropsychologia, 37, 661-670.
MANLY, T., ROBERTSON, I. H., & Verity, C. (1997). Developmental unilateral neglect: A single case study. Neurocase, 3, 19-29.
MANLY, T., WOLDT, K., WATSON, P., & Warburton, E. (2002b). Is motor perseveration in unilateral neglect 'driven' by the presence of neglected left-sided stimuli? Neuropsychologia, 40, 1794-1803.
MARCEL, A. J. (1998). Blindsight and shape perception: deficit of visual consciousness or of visual function? Brain, 121, 1565–1588.
MARCEL, A. J. (2000). On a Neurofunctional Theory of Visual Consciousness. Cognition and Consciousness, 9, 267-273.
MARCEL, A. J. (in press-a). Introspective report: Trust, self knowledge and science. Journal of Consciousness Studies.
MARCEL, A. J. (submitted). A tactile illusion induced by vision: modalities, frames of reference and unstable sensation.
MARCEL, A. J., & Dobel, C. (in press). Unstable frames of reference: perceptual input, imagery and self-consciousness. Perception.
MARCEL, A. J., Tegnér, R., & NIMMO-SMITH, I. (in press). Anosognosia for plegia: specificity, extension, partiality and disunity of bodily unawareness. Cortex.
MATTINGLEY, J. B., Driver, J., Beschin, N., & ROBERTSON, I. H. (1997). Attentional competition between modalities: Extinction between touch and vision after right hemisphere damage. Neuropsychologia, 35, 867-880.
MATTINGLEY, J. B., ROBERTSON, I. H., & Driver, J. (1998). Modulation of covert visual attention by hand movement: evidence from parietal extinction after right-hemisphere damage. Neurocase, 4, 245-253.
McIntosh, R. D., Brodie, E. E., Beschin, N., & ROBERTSON, I. H. (2000). Improving the clinical diagnosis of personal neglect: reformulating the comb and razor test. Cortex, 36, 289-292.
McKay, C. M., & CARLYON, R. P. (1999). Dual temporal pitch percepts from acoustic and electric amplitude-modulated pulse trains. Journal of the Acoustical Society of America, 105, 347-357
McKay, C. M., McDermott, H. J., & CARLYON, R. P. (2000) Place and temporal cues in pitch perception: are they truly independent?, Acoustics Research Letters Online (http://ojps.aip.org/ARLO/top.html), 1, 25-30. (See also Journal of the Acoustical Society of America, 108, 1385-1386).
McMillan, T., ROBERTSON, I. H., Brock, D., & Chorlton, L. (2002). Brief mindfulness training for attentional problems after traumatic brain injury: A randomised controlled trial. Neuropsychological Rehabilitation, 12, 117-125.
McMillan, T., ROBERTSON, I. H., & WILSON, B. A. (1999). Neurogenesis after brain injury: implications for neurorehabilitation. Neuropsychological Rehabilitation, 9, 129-133.
Mehta, M. A., OWEN, A. M., Sahakian, B. J., Mavaddat, N., Pickard, J. D., & Robbins, T. W. (2000). The effects of the stimulant methylphenidate on regional cerebral blood flow during performance of a working memory task. Journal of Neuroscience, 20.
Menon, D. K., OWEN, A. M., Williams, E. J., Kendall, I. V., Downey, S. P. M. J., Minhas, P. S., Allen, C. M. C., Boniface, S., Antoun, N., & Pickard, J. D. (1998). Cortical processing in the persistent vegetative state revealed by functional imaging. Lancet, 352, 200.
Menon, D. K., OWEN, A. M., Williams, E. J., Kendall, I. V., Downey, S. P. M. J., Minhas, P. S., Allen, C. M. C., Boniface, S., Antoun, N., & Pickard, J. D. (1999). Reply To: Schiff, N. and Plum. Trends in Cognitive Sciences, 3, 44-46.
Micallef, S., Anderson, J., Anderson, V., ROBERTSON, I. H., & MANLY, T. (2001). Sustained and selective attnetion in children with attention deficit/hyperactivity disorder and specific learning disabilities. Clinical Neuropsychological Assessment, 2, 1-23.
MICHEYL, C., & CARLYON, R. P. (1998). Effects of temporal fringes on fundamental-frequency discrimination. Journal of the Acoustical Society of America, 104, 3006-3018.
MICHEYL, C., CARLYON, R. P., SHTYROV, Y., HAUK, O., DODSON, T., & PULVERMULLER, F. (in press). Neurophysiological correlates of a perceptual illusion: A mismatch negativity study. Journal of Cognitive Neuroscience.
MICHEYL, C., Maison, S., CARLYON, R. P., Andeol, G., & Collet, L. (1999). Contralateral suppression of transiently-evoked otoacoustic emissions by harmonic complex tones in humans. Journal of the Acoustical Society of America, 105, 293-305.
MICHEYL, C., Moore, B. C. J., & CARLYON, R. P. (1998). The role of excitation-pattern cues and temporal cues in the frequency and modulation-rate discrimination of amplitude-modulated tones. Journal of the Acoustical Society of America, 104, 1039-1050.
O'Connell, J. E., French, J. M., ROBERTSON, I. H., & Gray, C. S. (1998). Artrial fibrillation and cognitive function: a case control study. Journal of Neurology, Neurosurgery and Psychiatry, 65, 386-389.
OWEN, A. M. (1997a). The functional organization of working memory processes within human lateral frontal cortex: The contribution of functional neuroimaging. European Journal of Neuroscience, 9, 1329-1339.
OWEN, A.M. (1997b). Tuning in to the temporal dynamics of brain activation using functional magnetic resonance imaging (fMRI). Trends in Cognitive Sciences, 1, 123-125.
OWEN, A.M. (1997c). Cognitive planning in humans: neuropsychological, neuroanatomical and neuropharmacological perspectives. Progress in Neurobiology, 53, 431-450,
OWEN, A. M. (1998). Memory: dissociating multiple memory processes. Current Biology, 8, 23, R850-852.
OWEN, A. M. (2000). The role of the lateral frontal cortex in mnemonic processing; The contribution of functional neuroimaging. Experimental Brain Research, 133, 33043.
OWEN, A. M., Doyon, J., Dagher, A., & Evans, A. C. (1998a). Abnormal basal-ganglia outflow in Parkinson's disease identified with positron emission tomography: Implications for higher cortical functions. Brain, 121, 5.
OWEN, A. M., Doyon, J., Dagher, A., & Evans, A. C. (1999a). Abnormal basal-ganglia outflow in Parkinson's disease identified with positron emission tomography: Implications forhigher cortical functions. Focus on Parkinson's disease, pp18-19.
OWEN, A. M., Herrod, N. J., Menon, D. K., Clark, J. C., Downey, S. P. M. J., Carpenter, T. A., Minhas, P. S., Turkheimer, F. E., Williams, E. J., Robbins, T. W., Sahakian, B. J., Petrides, M., & Pickard, J. D. (1999b). Redefining the functional organisation of working memory processes within human lateral prefrontal cortex. European Journal of Neuroscience, 11, 567-574.
OWEN, A. M., Iddon, J. L., HODGES, J. R., & Robbins, T. W. (1997). Spatial and non-spatial working memory at different stages of Parkinson's disease. Neuropsychologia, 35, 519-532.
OWEN, A. M., LEE, A., & Williams, C. H. (2000). Dissociating aspects of verbal working memory within the human frontal lobe: Further evidence for a 'process-specific' model of lateral frontal organization. Psychobiology, 28, 146-155.
OWEN, A. M., Menon, D. K., JOHNSRUDE, I. S., BOR, D., SCOTT, S. K., MANLY, T., Williams E. J., Mummery, C., & Pickard, J. D. (in press). Detecting residual cognitive function in persistent vegetative state (PVS). Neurocase.
OWEN, A. M., Stern, C. E., Look, R. B., Tracey, I., Rosen, B. R., & Petrides, M. (1998b). Functional organisation of spatial and non-spatial working memory processes within the human lateral frontal cortex. Proceedings of the National Academy of the USA. 95, 7721-7726.
Pantelis, C., Barber, F. Z., Barnes, T. R. E., Nelson, H. E., OWEN, A. M., & Robbins, T. W. (1999). A comparison of set-shifting ability in patients with schizophrenia and frontal lobe damage. Schizophrenia Research, 37, 251-270.
Park, N. W., Moscovitch, M., & ROBERTSON, I. H. (1999). Divided attention impairments after traumatic brain injury. Neuropsychologia, 37, 1119-1133.
Robbins, T. W., James, M., OWEN, A. M., Sahakian, B. J., McInnes, L., & Rabbitt, P. (1998). A study of performance on tests from the CANTAB battery sensitive to frontal lobe dysfunction in a large sample of normal volunteers: implications for theories of executive function and cognitive ageing. Journal of the International Neuropsychological Society, 4, 474-490.
ROBERTSON, I. H. (1998a). Controlling what we see and do. Current Biology, 8, 232-234.
ROBERTSON, I. H. (1999a). Cognitive rehabilitation: attention and neglect. Trends in Cognitive Science, 3, 385-393.
ROBERTSON, I. H. (1999b). Setting goals for rehabilitation. Current Opinion in Neurology, 23, 703-708.
ROBERTSON, I. H. (2000). Compensations for brain deficits. British Journal of Psychiatry, 176, 412-413.
ROBERTSON, I. H., & HAWKINS, K. (1999). Limb activation and unilateral neglect. Neurocase, 5, 153-160.
ROBERTSON, I. H., Hogg, K., & McMillan, T. M. (1998a). Rehabilitation of Unilateral Neglect: Improving Function by Contralesional Limb Activation. Neuropsychological Rehabilitation, 8, 19-29.
ROBERTSON, I. H., MANLY, T., ANDRADE, J., BADDELEY, B. T., & YIEND, J. (1997a). 'Oops!': Performance correlates of everyday attentional failures in traumatic brain injured and normal subjects. Neuropsychologia, 35, 747-758.
ROBERTSON, I. H., MANLY, T., Beschin, N., Haeske-Dewick, H., Hömberg, V., Jehkonen, M., Pizzamiglio, L., SHIEL, A., Weber, E., & Zimmerman, P. (1997b). Auditory Sustained Attention is a Marker of Unilateral Spatial Neglect. Neuropsychologia, 35, 1527-1532.
ROBERTSON, I. H., MATTINGLEY, J. B., RORDEN, C., & DRIVER, J. (1998). Phasic alerting of neglect patients overcomes their spatial deficit in visual awareness. Nature, 395, 169-172.
ROBERTSON, I. H., & MURRE, J. M. J. (1999). Rehabilitation of brain damage: Brain plasticity and principles of guided recovery. Psychological Bulletin, 125, 544-575.
ROBERTSON, I. H., Nico, D., & Hood, B. (1997c). Believing what you feel: Using proprioceptive feedback to reduce unilateral neglect. Neuropsychology, 11, 53-58.
ROBERTSON, I. H., RIDGEWAY, V., GREENFIELD, E., & PARR, A. (1997d). Motor recovery after stroke depends on intact sustained attention: A 2-year follow-up study. Neuropsychology, 11, 290-295.
Rogers, R. D., OWEN, A. M., Middleton, H. C., Pickard, J. D., Sahakian, B. J., & Robbins, T. W. (1999). Decision-making in humans activates multiple sites within inferior and orbital prefrontal cortex. Journal of Neuroscience, 20, 9029-9038.
RORDEN, C., & Driver, J. (1999). Does auditory attention shift in the direction of an upcoming saccade? Neuropsychologia, 37, 357-377.
RORDEN, C., HEUTINK, J., GREENFIELD, E., & ROBERTSON, I. H. (1999). When a rubber hand 'feels' what the real hand cannot. NeuroReport, 10, 135-138.
RORDEN, C., MATTINGLEY, J. B., Karnath, H., & Driver, J. (1996). Visual extinction and prior entry: Impaired perception of temporal order with intact motion perception after unilateral parietal damage. Neuropsychologia, 35, 421-433.
Rowe, J. B., OWEN, A. M., JOHNSRUDE, I. S., & Passingham, R. E. (2001). Imaging the components of a planning task. Neuropsychologia, 39, 315-327.
Rushworth, M. F. S., & OWEN, A. M. (1998). The functional organisation of the lateral frontal cortex: conjuncture or conjecture in the electrophysiology literature? Trends in Cognitive Sciences, 2, 46-53.
Sheppard, D. M., DUNCAN, J., Shapiro, K. L., & Hillstrom, A. P. (2002). Objects and events in the attentional blink. Psychological Science, 13, 410-415.
SIMONS, J., GRAHAM, K. S., OWEN, A. M., PATTERSON, K., & HODGES, J. R. (2001). Perceptual and semantic components of memory for objects and faces: A PET study. Journal of Cognitive Neuroscience, 13, 430-443.
Stern, C. E., OWEN, A. M., Petrides, M., Look, R. B., Tracey, I., & Rosen, B. R. (2000). Activity in ventrolateral and mid-dorsolateral prefrontal cortex during non-spatial visual working memory processing: Evidence from functional magnetic resonance imaging. Neuroimage, 11, 392-399.
Vandenberghe, R., DUNCAN, J., ARNELL, K. M., BISHOP, S. J., Herrod, N. J., OWEN, A. M., Minhas, P. S., Dupont, P., Pickard, J. D., & Orban, G. A. (2000). Maintaining and shifting attention within left or right hemifield. Cerebral Cortex, 10, 706-713.
van Wieringen, A., CARLYON, R. P., LONG, C. J., & WOUTERS, J. (submitted). Pitch of amplitude-modulated irregular-rate stimuli in acoustic and electric hearing..
Wiegrebe, L., PATTERSON, R. D., CARLYON, R. P., & Demany, L. (1998). Temporal dynamics of pitch strength for regular-interval noises. Journal of the Acoustical Society of America, 104, 2307-2313.
WILSON, F. C., MANLY, T., Coyle, D., & ROBERTSON, I. H. (2000). The effect of contralesional limb activation training and sustained attention training for self-care programmes in unilateral spatial neglect. Restorative Neurology and Neuroscience, 16, 1-4.
Winocur, G., Palmer, H., Stuss, D. T., Alexander, M. P., Craik, F. I. M., Levine, B., Moscovitch, M., & ROBERTSON, I. H. (2000). Cognitive rehabilitation in clinical neuropsychology. Brain and Cognition, 42, 120-123.
Books
Bermúdez, J., MARCEL, A. J., & Eilan, N. (Eds.). (1995). The body and the self. Cambridge, Mass: MIT Press.
Harrison, J. E., & OWEN, A. M. (2001). Cognitive deficits in neurological disorders. London: Dunitz.
Humphreys, G. W., DUNCAN, J., & Treisman, A. M. (Eds.). (1999). Attention, space, and action: Studies in cognitive neuroscience. Oxford: Oxford University Press.
Kanwisher, N., & DUNCAN, J. (in press). Attention and performance XX: Functional brain imaging of visual cognition. Oxford: Oxford University Press.
ROBERTSON, I. H., & Halligan, P. W. (1999). Spatial neglect: A clinical handbook for diagnosis and treatment. Hove: Psychology Press.
Schneider, W. X., OWEN, A. M., & DUNCAN, J. (2000). Executive control and the frontal lobe: Current issues. Berlin: Springer-Verlag.
Stuss, D. T., Winocur, G., & ROBERTSON, I. H. (1999). Cognitive rehabilitation. Cambridge: Cambridge University Press.
Book Chapters and Contributions
CARLYON, R. P. (1998). The effects of resolvability on the encoding of fundamental frequency by the auditory system. In A. R. Palmer, A. Rees, A. Q. Summerfield & R. Meddis (Eds.), Psychophysical and physiological advances in hearing. London: Whurr.
CARLYON, R. P., CUSACK, R., Foxton, J. M., & ROBERTSON, I. H. (2001d). Effects of attention and of unilateral neglect on auditory streaming. In D. J. Brebart, A. J. M. Houtsma, A. Kohlrausch, V. F. Prijs & R. Schoonhoven (Eds.), Physiological and psychophysical bases of auditory function. Maaastricht: Shaker.
Cools, R., Swainson, R., OWEN A. M., & Robbins, T. W. (1999). Cognitive Function in Non-Demented Parkinson's Disease. In E. C. H. Wolters, P.H Cheltens & H. W. Berendse (Eds.), Mental dysfunction in Parkinson's disease. Utrecht, The Netherlands: Academic Pharmaceutical Productions.
DUNCAN, J. (1996). Cooperating brain systems in selective perception and action. In T. Inui & J. L. McClelland (Eds.), Attention and performance XVI (pp. 549-578). Cambridge, MA: MIT Press.
DUNCAN, J. (1999). Attention. In R. A. Wilson & F. C. Keil (Eds.), The MIT encyclopedia of the cognitive sciences (pp. 39-41). Cambridge, MA: MIT Press.
DUNCAN, J. (2000). Visual attention in mind and brain. In J. J. Bolhuis (Ed.), Brain, perception, memory. Advances in cognitive neuroscience (pp. 49-68). Oxford: Oxford University Press.
DUNCAN, J. (2001b). Frontal lobe function and the control of visual attention. In J. Braun, C. Koch & J. L. Davis (Eds.), Visual attention and cortical circuits. Cambridge, MA: MIT Press.
DUNCAN, J., & Miller, E. K. (2002). Cognitive focus through adaptive neural coding in the primate prefrontal cortex. In D. T. Stuss & R. T. Knight (Eds.), Principles of frontal lobe function (pp. 278-291). Oxford: Oxford University Press.
DUNCAN, J., & OWEN, A. M. (2000b). Dissociative methods in the study of frontal lobe function. In S. Monsell & J. Driver (Eds.), Control of cognitive processes: Attention and performance XVIII (pp. 567-576). Cambridge, MA: MIT Press.
DUNN, B. D., OWEN , A. M., & Sahakian, B. J. Neuropsychological assessment of dementia. In J. O' Brien, D. Ames & A. Burns (Eds.), Dementia. Arnold.
Eilan, N., MARCEL, A. J., & Bermúdez, J. (1995). Self-Consciousness and the Body. In J. Bermúdez, Marcel, A. J., & Eilan, N. (Eds.), The Body and the self. Cambridge, Mass: MIT Press.
GOCKEL, H., CARLYON, R. P., & MICHEYL, C. (1999). The effect of lateralized temporal fringes on fundamental frequency discrimination. In T. Dau, V. Hohmann & B. Kollmeier (Eds.), Psychophysics, physiology and models of hearing. Singapore: World Scientific.
Harrison, J. E., & OWEN, A. M. (2001). Cognitive deficits in neurological disorders: Methodological considerations. In J. E. Harrison & A. M. OWEN (Eds.), Cognitive deficits in neurological disorders. London: Dunitz.
Harrison, J. E., Stow, I., & OWEN A. M. (2001). Parkinson's disease. In J. E. Harrison & A. M. OWEN (Eds.), Cognitive deficits in neurological disorders. London: Dunitz.
LEE, A. C. H. OWEN, A. M., Rogers, R., Sahakian, B. J., & Robbins, T. W. (2000). Utility of the CANTAB battery in functional neuroimaging. In M. Ernst & J. M. Rumsey (Eds.), Functional neuroimaging in child psychiatry (pp. 366-378). Cambridge, UK: Cambridge University Press.
LYZENGA, L., & CARLYON, R. P. (1999). Interference of formant-frequency modulation detection (FMDI) by off-frequency formants presented in several binaural schemes. In T. Dau, V. Hohmann & B. Kollmeier (Eds.), Psychophysics, physiology and models of hearing. Singapore: World Scientific.
MANLY, T. (in press). The Cognitive Rehabilitation of Attention Disorders. In B. A. WILSON (Ed.), Neuropsychological Rehabilitation:Theory and Practice. Swets.
MANLY, T., & MATTINGLEY, J. B. (in press). Visuo-spatial and attentional disorders. In L. Goldstein & J. McNeil (Eds.), Clinical neuropsychology: Practical guide to assessment and management for clinicians. Hove: Psychology Press.
MANLY, T., & ROBERTSON, I. H. (1997). Sustained Attention and the Frontal Lobes. In P. Rabbitt (Ed.), Methodology of frontal and executive function (pp. 135-150). Hove: Psychology Press.
MANLY, T., & ROBERTSON, I. H. (in press). The Rehabilitation of Attention. In P. W. Halligan, U. Kischka, & J. C. Marshall (Eds.), Oxford handbook of clinical neuropsychology. Oxford: Oxford University Press.
MANLY, T., WARD, S., & ROBERTSON, I. H. (2002). The Rehabilitation of Attention. In P. J. Eslinger (Ed.), Neuropsychological interventions: Emerging treatment and management models for neuropsychological impairments.
MARCEL, A. J. (1994). What is relevant to the unity of consciousness? In C. Peacocke (Ed.), Objectivity, simulation and the unity of consciousness. Proceedings of the British Academy, 83, 79-88.
MARCEL, A. J. (in press-b). The sense of agency: Awareness and ownership of actions and intentions. In J. Roessler & N. Eilan (Eds.), Agency and self awareness. Oxford: Oxford University Press
OWEN, A. M. (1999). Functional neuroimaging: Recent contributions to neuropsychology, psychiatry and behavioural neurology. In Jose M. Olivares (Ed.), Investigation en psiquiatria. Spain.
OWEN, A. M. (2001). The Neuropsychological Sequelae of Frontal-Lobe damage. In J. E. Harrison and A. M. OWEN (Eds), Cognitive deficits in neurological disorders. London: Dunitz
OWEN A. M. (in press). Cognitive planning in humans: New insights from the Tower of London task. In R. G. Morris & G. Ward (Eds.), The psychological of planning: Cognitive and Neuropsychological Perspectives.
OWEN A. M., & Doyon, J. (1999c). The Cognitive neuropsychology of Parkinson's disease: A functional neuroimaging perspective. In G. Stern (Ed.), Parkinson's disease (advances in neurology) (pp 49-56). Lippincott-Raven Press.
OWEN, A. M., EPSTEIN, R., & JOHNSRUDE, I. S. (2001). fMRI: Applications to cognitive neuroscience. In P. Jezzard, P. M. Matthews & S. M. Smith (Eds.), Functional magnetic resonance imaging of the brain: Methods for neuroscience (pp. 311-327). Oxford: Oxford University Press.
OWEN A. M., & Robbins, T. W. (submitted). Attention and working memory in movement disorders. In M. Jahanshahi & R. Brown (Eds.), The neuropsychology of movement disorders.
OWEN A. M., Sahakian, B. J., & Robbins, T. W. (1998c). The role of executive deficits in memory disorders in neurodegenerative disease. In A. I. Troster (Ed.), Memory in neurodegenerative disease: Biological, cognitive and clinical perspectives. Cambridge: Cambridge University Press.
Robbins, T. W., James, M. OWEN, A. M., & Sahakian, B. J. (1997). A neural systems approach to the cognitive psychology of ageing:studies with CANTAB on large samples of the normal elderly population. In P. Rabbitt (Ed.), Methodology of frontal and executive function. Sussex: Lawrence Erlbaum Associates.
Robbins, T. W., OWEN, A. M., & Sahakian, B. J. (1998). The neuropsychology of basal ganglia disorders; An integrative cognitive and comparative approach. In M. Ron & A. David (Eds.), Disorders of brain and mind. Cambridge: Cambridge University Press, 1998.
ROBERTSON, I. H. (1998b). Theory-driven neuropsychological rehabilitation: the role of attention and competition in recovery of function after brain damage. In D. Gopher & A. Koriat (Eds.), Attention and performance XVII. Cambridge, MA: MIT Press.
ROBERTSON, I. H. (1999). The Rehabilitation of Attention. In D. T. Stuss, G. Winocur, & I. H. ROBERTSON (Eds.), Cognitive rehabilitation (pp. 302-313). Cambridge: Cambridge University Press.
ROBERTSON, I. H., & MANLY, T. (1999). Sustained Attention Deficits in Time and Space. In G. W. Humphreys, J. DUNCAN, & A. M. Treisman (Eds.), Attention, space, and action: Studies in cognitive neuroscience. Oxford: Oxford University Press.
TINSLEY, C. J., & EVERLING, S. (in press). Contribution of the primate prefrontal cortex to the gap effect. In D. Munoz (Ed.), The brain's eye: Neurobiological and clinical aspects of oculomotor research. Amsterdam: Elsevier.
Theses
BLACKWELL, A. (1999). Metaphor in diagrams.
BOR, D. (2002). The role of the prefrontal cortex in strategic processes, as revealed by spatial span.
BRIGHT, P. (1998). The control of action: An exploration of Spearman's general factor.
CLAPP, S. (1999). Attention and sensory processing for balance.
GREEN, H. (1999). The development, correlates and causes of negative priming.
PEERS, P. (2002). Categorisation of attentional deficits following unilateral brain lesions.

Conference Proceedings and Published Abstracts
Armilio, M. L., Picton, T. W., ROBERTSON, I. H., & Stuss, D. T. (1999). Electrophysiological correlates of response inhibition and error processing in traumatic brain injured and normal subjects. Journal of Cognitive Neuroscience, 11, Suppl, 65.
BOR, D., DUNCAN, J., Navaddat, N., Williams, E. J., Pickard, J. D., & OWEN, A. M. (1999). Dissociation of function within the human lateral frontal cortex. NeuroImage 9, S330.
BOR, D., DUNCAN, J., & OWEN, A. M. (2000). Lateral prefrontal cortex activity may be modulated by the configuration of stimuli in a spatial working memory task. Society for Neuroscience Abstracts, 26, 560.16.
BOR, D., DUNCAN, J., & OWEN, A.M. (2001). Organised working memory lists decrease task difficulty but increase activation in the lateral frontal cortex. Society for Neuroscience Abstracts, 27, 80.3.
BOR, D., OWEN, A.M., & DUNCAN, J. (2001). Prefrontal cortex activation increases in association with an easier variant of the spatial span task. NeuroImage 13, S301.
BRETT, M., Christoff, K. CUSACK, R., & Lancaster, J. (2001). Using the Talairach atlas with the MNI template. NeuroImage, 13, S85.
CARLYON, R. P. (1999). Auditory processing of coherent and incoherent frequency modulation (invited paper). Journal of the Acoustical Society of America, 105, part 2, 1188.
CARLYON, R. P., CUSACK, R., Foxton, J. M., Aikman, G. A., & ROBERTSON, I. H. (2000). Effects of attention on auditory stream segregation. British Journal of Audiology, 34, part 2, 12-113.
CARLYON, R. P., & DEEKS, J. M. (2001). Limits on rate discrimination: implications for acoustic and electric hearing, Association for Research in Otolaryngology, 24th Midwinter Research Meeting (ISSN-0742-3152), p 293. Also available at http://www.aro.org.
CARLYON, R. P., & DEEKS, J. M. (2001). Limits on temporal pitch perception: implications for acoustic and electric hearing. British Journal of Audiology, 35, 153-155.
CARLYON, R. P., & Demany, L. (1999). Competition between space and time in the auditory system. Journal of the Acoustical Society of America, 105, part 2, 1389.
CARLYON, R. P., & Demany, L. (1999). Competition between space and time in the auditory system. British Journal of Audiology, 33, 118-119.
CARLYON, R. P., Geurts, L., & Wouters, J. (1998). Across-channel sensitivity to temporal asynchrony in cochlear implantees. Proceedings of the 16th International Congress on Acoustics. Seattle, Washington: USA.
CARLYON, R. P., LONG, C. J., van Wieringen, A., WOUTERS, J., & Vanat, Z. (2002). Temporal pitch perception: measurements from acoustic and electric hearing. International Journal of Audiology, 41, part 4.
CARLYON, R. P., Plack, C. J., & CUSACK, R. (2001). Cross-modal and cognitive influences on the build-up of auditory streaming. British Journal of Audiology, 35, 139-140.
CARLYON, R. P., & Shamma, S. (2002). Monaural phase sensitivity: All in the ear?, Association for Research in Otolaryngology, 25th Midwinter Research Meeting (ISSN-0742-3152), p 195. Also available at http://www.aro.org.
CLAPP, S., MANLY, T., & WING, A. M. (1998). A case study of impaired balance during cognitive activity. Journal of Cognitive Neuroscience, 10, Suppl, 93.
Cools, R., Clark, L., OWEN, A. M., & Robbins, T. W. (2002). Defining the neural mechanisms of probabilistic reversal learning using event-related fMRI. Neuroimage, 16, 2218-2219.
Cools, R., Stefanova, E., Barker, R. A., Robbins, T. W., & OWEN, A. M. (2001a). Dopaminergic regulation of high-level cognition in Parkinson's disease through modulation of cortico-striatal circuitry revealed by PET. Society for Neuroscience Abstracts, 27, 540.4.
Cools, R., Stefanova, E., Barker, R. A., Robbins, T. W., & Owen, A. M. (2001b). Dopaminergic modulation of high-level cognition in Parkinson's disease. The role of prefrontal cortex and basal ganglia revealed by PET. Neuroimage , 13, S652.
COX, S. M. L., ANDRADE, A., & JOHNSRUDE, I. S. (in press). Functional imaging of conditioned preferences. Society for Neuroscience Abstracts.
CUSACK, R., & CARLYON, R. P. (2000). Auditory pop-out: Perceptual asymmetries in sequences of sounds. British Journal of Audiology, 34, part 2, p 112.
CUSACK, R., & CARLYON, R. P. (in press). Auditory feature extraction revealed by search asymmetries. Society for Neuroscience Abstracts.
CUSACK, R., CARLYON, R. P., JOHNSRUDE, I., & EPSTEIN, R. (2001). Functional interaction between left and right auditory pathways in or before auditory cortex demonstrated using fMRI. Society for Neuroscience Abstracts, 27, 512.11.
CUSACK, R., CARLYON, R. P., & ROBERTSON, I. H. (1999a). Comparisons between but not within sounds are impaired in stroke victims with unilateral neglect . Journal of the Acoustical Society of America, 105, part 2, 1236.
CUSACK, R., CARLYON, R. P., & ROBERTSON, I. H. (1999b). Neglect between but not within auditory objects, Proc. Cognitive Neuroscience Society Annual meeting. Journal of Cognitive Neuroscience, 11, Suppl, 58.
CUSACK, R., CARLYON, R. P., & ROBERTSON, I. H. (2000). Unilateral neglect affects the auditory domain in time more than space. Journal of Cognitive Neuroscience, 12, Suppl, 87.
CUSACK, R., Papadakis, N., Martin, K., & BRETT, M. (2001). A new robust 3d phase-unwrapping algorithm applied to fMRI field maps for the undistortion of EPIs. NeuroImage 13, S103.
DEEKS, J. M., CARLYON, R. P., NORRIS, D., & BUTTERFIELD, S. (2001). The continuity illusion and vowel identification. British Journal of Audiology, 35, 142-143.
DOBLER, V., MANLY, T., ROBERTSON, I. H., Polichroniadis, M., Verity, C., Goodyer, I., & WILSON, B. A. (2001). Modulation of hemispatial attention in a case of developmental unilateral neglect. Neurocase, 7, 186.
DOVE, A., EPSTEIN, R., GRAHAM, K. S., BRETT, M., OWEN, A. M. (2002). Encoding and retrieval of abstract paintings, faces and places: The role of intention. Neuroimage, 16, 614-615.
DOVE, A., Rowe, J. B., BRETT, M., & OWEN, A. M. (2001). Neural correlates of passive and active encoding and retrieval: A 3T fMRI study. NeuroImage, 13, S660.
DUNCAN, J. (2001). An adaptive coding model of prefrontal function. NeuroImage, 13, S1300.
DUNCAN, J., & OWEN, A. (1999). Common regions of the human frontal lobe recruited by diverse cognitive demands. Society for Neuroscience Abstracts, 25, 620.12.
DUNCAN, J., Seitz, R. J., KOLODNY, J., BOR, D., Herzog, H., AHMED, A., NEWELL, F., & EMSLIE, H. (2000). A neural basis for general intelligence. Society for Neuroscience Abstracts, 26, 201.12.
EPSTEIN, R., & Kanwisher, N. (2001). Mnemonic functions of the parahippocampal place area: An event-related fMRI study. NeuroImage, 13, S663.
EVERLING, S., TINSLEY, C. J., Gaffan, D., & DUNCAN, J. (2000). Neural activity in a focused attention task in monkey prefrontal cortex. Society for Neuroscience Abstracts, 26, 837.18.
GOCKEL, H., & CARLYON, R. P. (1999). Effects of lateralized fringes on fundamental-frequency discrimination. British Journal of Audiology, 33, 117-118.
GOCKEL, H., & CARLYON, R. P. (2001). Non-simultaneous FMDI. British Journal of Audiology, 35, 130-131.
GOCKEL, H., CARLYON, R. P., & Micheyl, C. (1999). Fundamental frequency discrimination: Influence of lateralized temporal fringes. Journal of the Acoustical Society of America, 105, part 2, 1388.
GOCKEL, H., CARLYON, R. P., & Moore, B. C. J. (2000). Pitch of asymmetrically frequency-modulated tones. British Journal of Audiology, 34, part 2, p 99.
JOHNSRUDE, I. S., CUSACK, R., Morosan, P., Hall, D., BRETT, M., Zilles, K., & Frackowiak, R. (2001). Cytoarchitectonic region-of-interest analysis of auditory imaging data. NeuroImage, 13, S897.
LEE, A. C. H., Manes, F. F., Bor, D., Robbins, R. W., & OWEN, A. M. (2000). Dissociating planning and working memory processes within the human lateral frontal cortex. Society for Neuroscience Abstracts, 26, 749.6.
LEE, A. C. H., Robbins, T. W., GRAHAM, K. S., & OWEN, A. M. (2001). Dissociation of semantic and episodic memory using positron emission tomography and a novel homophone task. Society for Neuroscience Abstracts, 27, 639.8.
LEE, A. C. H., Robbins, T. W., Pickard, J. D., & OWEN, A. M. (1999a). Asymmetric frontal activation during episodic memory: the effects of stimulus type on encoding and retrieval. NeuroImage, 9, S955.
LEE, A. C. H., Robbins, T. W., Pickard, J. D., & OWEN, A. M. (1999b). Episodic memory encoding and retrieval: a combined PET and functional MRI study. Society for Neuroscience Abstracts, 25, 259.4.
Lewis, S. J. G., DOVE, A., Cools, R., Robbins, T. W., Barker, R. A., & OWEN, A. M. (2001). Specifying The Executive Deficit In Parkinson's Disease; A Combined Behavioural And Event-Related fMRI Study. Society for Neuroscience Abstracts, 27, 311.13.
LONG, C. J., CARLYON, R. P., McKay, C. M., & Vanat, Z. (2002a). Temporal pitch perception: Examination of first-order intervals. International Journal of Audiology, 41, part 4.
LONG, C. J., CARLYON, R. P., van Wieringen, A., WOUTERS, J., McKay, C. M., DEEKS, J. M., & Vanat, Z. (2002b). Temporal pitch perception in acoustic and electric hearing, Association for Research in Otolaryngology, 25th Midwinter Research Meeting (ISSN-0742-3152), p 121. Also available at http:///www.aro.org
LYZENGA, J., & CARLYON, R. P. (1999). Direction discrimination for formant-frequency glides and modulation. Journal of the Acoustical Society of America, 105, part 2, 1153
MANLY T., DATTA A., HEUTINK J., HAWKINS K., CUSACK R., RORDEN C., & ROBERTSON I. H. (2000). An electophysiological predictor of imminent action error in humans. Journal of Cognitive Neuroscience, 12, Suppl, 111.
MANLY, T., HAWKINS, K., EVANS, J., & ROBERTSON, I. H. (2001a). Rehabilitation of Executive Function: Facilitation of effective goal management on complex tasks using periodic auditory alerts. Neurocase, 7.
MANLY, T., OWEN, A. M., DATTA, A., Lewis, G., SCOTT, S., RORDEN, C., Pickard, J., & ROBERTSON, I. H. (2001). Busy doing nothing?': Increased right frontal and parietal activation associated with self-sustained attention to an 'unchallenging' task. NeuroImage, 13, S331.
MANLY, T., & ROBERTSON, I. H. (1998). Sustained attention following traumatic brain injury. Journal of Cognitive Neuroscience, 10, Suppl, 67.
MARCEL, A. J. (2000). Actions are under a description: What you can do depends on what you intend. British Association for the Advancement of Science.
NIMMO-SMITH, I., & DUNCAN, J. (2001). Comparing regional distributions of activation in neuroimaging studies. NeuroImage, 13, S213.
OSSWALD, K., DUNCAN, J., Logan, G. D., & BRETT, M. (in press). Automatic response selection - functional imaging of practice effects. Society for Neuroscience Abstracts.
OWEN, A. M., Gould, R. L., Brown, R. G., DOVE, A., Ffytche, D. H., WOJCIULIK, E., & Howard, R. (2001). Object-Location Memory Examined Using Fmri; Contrasting Measures Of Difficulty And The Implications For Studies Of Patients. Society for Neuroscience Abstracts, 27, 74.3.
OWEN, A. M., Lewis, S. J. G., DOVE, A., Robbins, T. W., CUSACK., R., & Barker, R. A. (2002). Dissociating the effects of disease and behaviour in Parkinson's disease using event-related fMRI. Neuroimage, 16, 2336-2337.
OWEN, A. M., Menon, D. K., Williams, E. J., Minhas, P. S., JOHNSRUDE, I. S., SCOTT, S. K., Allen, C. M. C., Boniface, J., Kendall, I. V., Downey, S. P. M. J., Antoun, N., Clark, J., & Pickard, J. D. (1999a). Functional imaging in persistent vegitative state (PVS). NeuroImage 9, S581.
OWEN, A. M., Menon, D. K., Williams, E. J., Minhas, P. S., JOHNSRUDE, I. S., SCOTT, S. K., Allen, C. M. C., Boniface, S. J., Kendall, I. V., Downey, S. P. M. J., Antoun, N., Clark, J.C., MANLY, T., & Pickard, J. D. (1999b). Detecting residual cognitive function in persisitent vegetative state (PVS) using functional neuroimaging. Society for Neuroscience Abstracts, 25, 444.10.
PEERS, P., LUDWIG, C., RORDEN, C., CUSACK, C., Driver, J., Bundesen, C., DUNCAN, J. (2002). Using Bundesen's theory of visual attention to quantify attentional deficits following unilateral brain injury. Journal of Cognitive Neuroscience, 14, Suppl, 19.
Rice, C. D., Done, D. J., MANLY, T., & McKenna, P. J. (2002). Schizophrenic patients with symptoms show more impairment than those without symptoms on an ecologically valid test of executive function. Schizophrenia Research, 53, supplement, 133.
RODD, J. M., Davis, M. H., Johnsrude, I. S., & Owen, A. M. (2002). Am fMRI study of semantic ambiguity. Society for Neuroscience Abstracts.
Rowe, J. B., OWEN, A. M., JOHNSRUDE, I. S., & Passingham, R. (1999). Imaging the mental components of a planning task. Society for Neuroscience Abstracts, 25, 44.11.
Rypma, B., DUNCAN, J., Berger. J.S., McClintock, C. M., & D'Esposito, M. D. (2001). Neural correlates of individual differences in executive control: an event related fMRI study of processing speed and learning. Society for Neuroscience Abstracts, 27, 782,12.

TRANSFER TO HEALTH SERVICE

There has been a strong emphasis on the transfer of research findings relevant to rehabilitation and assessment to the NHS. Robertson and Manly have presented numerous workshops and clinical lectures to NHS professional groups in both community and hospital settings and have been active in training and post-graduate programmes of clinical psychologists. The ongoing programme of clinical workshops at the Oliver Zangwill Centre draws heavily upon the Unit's work. Assessment instruments for adults and children derived from studies in the Attention Group are now very widely used throughout the UK (and internationally). The work of Robertson and colleagues on limb activation therapy for unilateral neglect has now been widely adopted within stroke medicine services and the recent work of Robertson, Duncan and colleagues on Goal Management Training is having increasing influence on services, forming a central part, for example, of the programme for remediation and management of dysexecutive deficits at the Oliver Zangwill Centre.

EXTERNAL GRANTS

Carlyon, R. P. (1999-2001). Perceptual segregation and fusion of electrical stimulation by cochlear implant users. Defeating Deafness (The Hearing Research Trust). £9,127.
Carlyon, R. P., & Wouters, J. (1999-2001). The perception of electrical stimulation by cochlear implantees. The Royal Society. £4,020.
Carlyon, R. P. (1999-2003). Segregating concurrent sounds in acoustic and electric hearing. The Leverhulme Trust. £94, 630.
Carlyon, R. P., & Long, C. J. (2003-2006). Improving speech perception and localisation by cochlear implant users. Royal National Institute for Deaf People. £146,940.
Duncan, J., & Driver, J. (1996-1999). Psychoanatomical studies of extinction after brain injury: Attentional competition and integration. Wellcome Trust. £154,609.
Duncan, J. et al. (2001-2004). Neural basis of nonspatial visual attention: Objects, features and behaviour. Human Frontier Science Program. US$750,000.
Duncan, J., & Bobes-Leon, A. (2002). Neurophysiological basis of the attentional blink. Royal Society International Exchange Programme. £1,500.
Manly, T., & Robertson I. H. (1997-1999). Attentional problems following closed head injury. Pearl Assurance. £40,000.
Manly, T., Robertson, I. H., & Anderson, V. (1996-1998). Development of attentional skills in school age children. Australian Research Council. A$19,617.
Micheyl, C. (1998). Temporal processing in pitch perception. Centre National pour la Recherche Scientifique. £5,900.
Moore, B. C. J., & Carlyon, R. P. (2000-2003). Processing of dynamic frequency changes by the auditory system. Engineering and Physical Sciences Research Council. £131,155.
Plack, C. J., & Carlyon, R. P. (2002-2005). Mechanisms of pitch perception. Engineering and Physical Sciences Research Council. £201,016.
Robertson, I. H., & McMillan, T. (1995-1998). Attentional control training for closed head injury. NHS R & D Committee on Complex Disabilities. £134,000.
Robertson, I. H., & McMillan, T. (1995-1998). Neurophysical rehabilitation for neglect following stroke. NHS R & D Committee on Complex Disabilities. £125,000.
Robertson, I. H., & Mattingley, J. (1996-1998). Recovery of motor function following stroke: the role of attention. Stroke Assocation. £57,000.
Robertson, I. H. (1996-1998). Sustained attention training following right hemisphere damage. Stroke Association. £57,000.
Robertson, I. H., et al. (1997-1999). Rehabilitation of attention processes in TBI patients. Ontario Mental Health Foundation. C$41,310.
Robertson, I. H., & Monsell, S. (1998-2000). Impulsivity and preservation following stroke. Stroke Association. £81,000.
Robertson, I. H., Manly, T., & Picton, T. (1998-2000). Rehabilitation of attentional problems in traumatic brain injury. James McDonnell Foundation. US$60,000.
Robertson, I. H., et al. (1998-2001). Frontal lobes: fractionation, localization and rehabilitation of attentional disorders. C$756,510.
Robertson, I. H., Manly, T., et al. (1998-2002). Rehabilitation of frontal lobe disorders in focal lesions and normal ageing. James McDonnell Foundation. US$ 600,000.
Wouters, J., & Carlyon, R. P. (1999-2002). Perception of electrical stimulation via cochlear implants. Research Council of the Catholic University of Leuven. £131,255.

PRINCIPAL COLLABORATORS
Dr. V. Anderson, University of Melbourne, Melbourne
Dr. N. Antoun, Addenbrooke's Hospital, Cambridge
Mr. D. Baguley, Mr. P. Axon, Ms. Z. Vanat, Addenbrooke's Hospital, Cambridge
Dr. R. Barker, MRC Centre for Brain Repair, Cambridge
Professor J-C. Baron, Department of Medicine, University of Cambridge, Cambridge
Professor E. Bisiach , Universitá di Torino, Turin
Professor E. Bullmore, Department of Psychology, University of Cambridge, Cambridge
Dr. C. Bundesen, Copenhagen University, Copenhagen
Dr. L. Chelazzi, University of Verona, Verona
Dr. J. Cole, Poole Hospital, Southampton
Dr. R. Desimone, NIMH, Bethesda
Dr. G. DiGirolamo, Department of Experimental Psychology, University of Cambridge, Cambridge
Dr. C. Dobel, WW Universität Münster, Münster
Dr. J. Driver, University College, London
Dr. C. Fraser, Addenbrooke's Hospital, Cambridge
Professor I. Goodyer, Department of Developmental Psychiatry, University of Cambridge, Cambridge
Professor T. Holland. Department of Psychiatry, University of Cambridge, Cambridge
Dr. G. Humphreys, University of Birmingham, Birmingham
Dr. J Jolles, University of Maastricht, Maastricht
Dr. N. Kanwisher, MIT, Boston
Dr. R. Kentridge, University of Durham, Durham
Dr. S. Kirker, Addenbrooke's Hospital, Cambridge
Dr. E. Làdavas, Universitá di Bologna, Bologna
Dr. J. Lambie, Anglia Polytechnic University, Cambridge
Dr. S. Lewis, MRC Centre for Brain Repair, Cambridge
Professor P. M. Mathews, University of Oxford, Oxford.
Dr. C. McKay, Dr. H. McDermott, University of Melbourne, Melbourne
Dr. T. McMillan, Wolfson Rehabilitation Centre, London
Professor D. Menon, Department of Anaesthesia, University of Cambridge, Cambridge
Dr. E. Miller, MIT, Boston
Professor B C. J. Moore, Department of Experimental Psychology, University of Cambridge, Cambridge
Dr. D. Nico, Dr. G. Antonucci, Professor L. Pizzamiglio, Universitá di Roma La Sapienza, Rome
Dr. J. Parkinson, Department of Anatomy, University of Cambridge, Cambridge
Professor J. Pickard, Wolfson Brain Imaging Centre, University of Cambridge, Cambridge
Professor C. J. Plack, University of Essex, Colchester
Dr. A. C. Roberts, Department of Anatomy, University of Cambridge, Cambridge
Professor T. W. Robbins, Department of Experimental Psychology, University of Cambridge, Cambridge
Dr. J-P. Roll, Université de Provence, Marseille
Dr. R. Rogers, University of Oxford, Oxford
Dr. B. J. Sahakian, Department of Psychiatry, University of Cambridge, Cambridge
Professor S. Shamma, University of Maryland, Baltimore
Dr. S. Stern, Boston University, Boston
Dr. D. Stuss, Dr. T. Picton, Dr. B. Levine, Rotman Institute, Toronto
Dr. R. Tegnér, Karolinska Hospital, Stockholm
Dr. M. Valdes-Sosa, Cuban Center for Neuroscience, Havana
Professor G. Vallar, Universitá di Milano Bicocca, Milan
Dr. V. Walsh, University College, London
Dr. E. Warburton, Addenbrooke's Hospital, Cambridge
Professor A. Wing, University of Birmingham, Birmingham
Professor J. Wouters, Dr. A. van Wieringen, University of Leuven, Leuven.

Other sections in the 1998-2002 report

1. SUMMARY

2. ATTENTION GROUP

3. COGNITION AND EMOTION GROUP

4. LANGUAGE AND COMMUNICATION GROUP

5. MEMORY AND KNOWLEDGE GROUP: DMS SECTION

6. MEMORY AND KNOWLEDGE GROUP: REHABILITATION SECTION

7. METHODS RESEARCH AND INFRASTRUCTURE GROUP