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Vacation placement projects - 2010
1 Individual differences in cognitive control to food reward
2 Barking up the right tree in the absence of attention?
3 The influence of facial expression and individual differences on sensitivity to the perception of eye gaze.
4 Visual short-term memory and intelligence
5 Proposal for summer placement project "Optimal stimulus selection for neuroimaging experiments on semantic word variables"
6Individual differences in rhythm perception
1) Individual differences in cognitive control to food reward
Elisabeth von dem Hagen, Raliza Stoyanova, Luca Passamonti, Andy Calder
Recent data indicate that neural responses to rewarding visual food cues differ based not only on physiological states such as hunger (e.g., LaBar et al., 2001) but also based on self-reported sensitivity to reward (Beaver et al., 2007), sensitivity to the sight and smell of food (Passamonti et al., in prep) and dietary restraint (delParigi et al., 2007). Previous research from our lab (Beaver et al., 2007) has reported that individual differences in reward drive predict the degree of activation to appetizing stimuli in fronto-striatal-amygdala-midbrain network, and more recently Passamonti et al. (in preparation) has found that individuals high in sensitivity to the sight and smell of food show heightened negative connectivity between the anterior cingulate cortex and the nucleus accumbens indicating that they experience more conflict and/or exert poor cognitive control when faced with appetizing food cues. In the study proposed here, we are interested in further investigating the degree to which subjects can adjust cognitive control in the presence of rewarding food stimuli, as well as examining the degree to which individual difference measures in personality modulate performance. To this end, we will use a modified version of the emotional Stroop task. Previous research has shown that behaviourally individuals respond faster and more accurately on an incongruent Stroop trial if it has been preceded by an incongruent trial as compared to a congruent one, and that this effect may result from greater cognitive control due to the high conflict in the preceding incongruent trial (Kerns et al., 2004). In our proposed study, participants will be presented images of appetizing, disgusting or bland foods which they are asked to ignore while deciding the valence (positive/negative/neutral) of words overlaid on the images. These words may be emotionally congruent with the images (i.e., a positive word on an appetizing image or an aversive word on a disgusting image), emotionally incongruent (i.e., a positive word over a disgusting image or an aversive word over an appetizing image) or neutral (neutral words over bland food images). This work will inform an important aspect of a larger project on eating and cognitive control, currently underway in the E1 group, and will be the basis for subsequent functional imaging studies.
The visiting student will be expected to play a role in the design of the experiment (e.g. selection of appropriate images and words, timing of the experiment, e-prime scripting, etc) as well as running the experiment (recruiting and testing subjects) and carrying out data analysis (including discussion of these results at group meetings). The benefits to the student will include first-hand experience in carrying out a scientific experiment from its inception through to the analysis and dissemination of results. In addition to regular meetings and discussions specific to this project, the student will also benefit from attendance at E1 and Emotion group meetings and exposure to the wider research occurring at the CBU. The student will also be directly exposed and involved in other research within the E1 group including the opportunity to participate in functional imaging studies.
2) Barking up the right tree in the absence of attention?
Matt Davis, Bob Carlyon, Adrian Owen, Ingrid Johnsrude, Jenni Rodd
Functional imaging in healthy, awake volunteers shows additional activation in bilateral inferior frontal and left inferior temporal regions during comprehension of sentences containing ambiguous words such as bark or rain/reign (Rodd, Davis & Johnsrude, 2005). This neural correlate of semantic processing of speech has been used as a marker of intact sentence comprehension in vegetative state patients (Coleman, et al., 2007). Convergent evidence from participants sedated with an anaesthetic drug (Propofol), similarly suggests that ambiguity resolution is a high-level cognitive process that depends on conscious awareness (Davis, et al., 2007). However, since this hypothesis has not yet been tested in healthy, awake volunteers the generality of this finding remains in doubt. We therefore propose to combine the sentence materials developed by Rodd et al. (2005) with manipulations of attention similar to those used in recent studies of speech perception and attention (e.g. Pulvermuller et al., 2008). We will use fMRI to assess activation differences between high and low ambiguity sentences in the presence and absence of directed attention to those sentences. We will also collect post-scan sentence recognition scores so as to relate neuroimaging activity to subsequent memory for attended and unattended sentences.
The student will:
- Divide an existing set of ambiguous and unambiguous sentences (Rodd et al., 2005) into matched sets to appear in "attended" and "unattended" conditions.
- Use existing Praat scripts to convert certain of these sentences into non-speech, signal correlated buzzes and noises.
- Conduct pilot tests to assess the impact of different competing auditory and/or visual tasks on sentence comprehension and recognition memory
- Generate DMDX files to present attended and unattended stimuli in the scanner, derived from existing scripts
- Work with others to collect fMRI data from a group of volunteers (n =18)
- Preprocess and analyze fMRI data using SPM5 and modifications of existing Matlab scripts
We anticipate that by the end of the placement, summer student will have generated group activation maps for contrasts between speech and non-speech, high and low ambiguity sentences during directed and diverted attention. Results of these contrasts will provide an initial indication of which neural correlates of speech perception and comprehension depend on attention.
The dataset collected during this project will also support further correlation analyses relating between-item and between-participant variation in sentence memory and directed attention to neural activity. These will be conducted by the senior scientist and collaborators after the end of the summer placement.
References:
Coleman M.R., Rodd J.M., Davis M.H., Johnsrude I. S., Menon D.K. Owen A.M. (2007) Do vegetative patients retain aspects of language comprehension? Evidence from fMRI. Brain, 130, 2494-2507
Davis M.H., Coleman M.R., Absalom A.R., Rodd J.M., Johnsrude I. S., Matta B. F., Owen A.M., Menon D.K. (2007) Dissociating speech perception and comprehension at reduced levels of awareness. Proceedings of the National Academy of Sciences of the USA, 104(41), 16032-16037.
Pulvermüller, F., Shtyrov, Y., Hasting, A. S. and Carlyon, R.P. (2008) Syntax as a reflex: Neurophysiological evidence for early automaticity of grammatical processing, Brain and Language, 104(3), 244-253.
Rodd, J. M., Davis, M.H. & Johnsrude, I.S. (2005) Neural mechanisms of speech comprehension: fMRI studies of semantic ambiguity. Cerebral Cortex, 15(8), 1261-1269
3) The influence of facial expression and individual differences on sensitivity to the perception of eye gaze.
Michael Ewbank, Andy Calder
Individual responses to facial expressions vary across subjects. For example, some individuals may perceive an angry face as threatening, eliciting anxiety, while others may perceive it as a hostile challenge, provoking an aggressive response. Furthermore, whether one is the subject of another individual's gaze or not is a crucial factor in interpreting the meaning underlying the expression. Our recent research has shown that the neural response to angry and fearful faces is dependent upon individual differences in anxiety and spatial attention (Ewbank et al., submitted). Previous research from the group also indicated that differences in BAS-drive (or reward sensitivity) modulate the amygdala and prefrontal response to angry faces (Beaver et al., 2007).
Eye gaze has also been shown to influence the perception of facial expression; with direct gaze facilitating the recognition of angry faces, and averted gaze enhancing the perception of fearful faces (Adams & Kleck, 2003). Our recent imaging work also indicates that the amygdala response to facial expressions is modulated by the direction of gaze, and that this relationship is correlated with individual levels of anxiety (Ewbank et al., in prep). However, little research has investigated how emotional expressions can modulate the perception of gaze, with the exception of one study; showing increased perception of mutual gaze with happy expressions (Martin & Rovira, 1982). Recent work has identified individual thresholds in the perception of another's gaze; termed the 'cone of gaze' i.e. the distance between which left and right gaze is perceived as looking directly at the observer (Gamer & Hecht, 2007). Our study intends to investigate how facial expression and personality traits modulate this cone of gaze. The influence of personality has important implications for understanding how disorders such as social anxiety and aggressive behaviour impact on social interactions.
In our proposed study subjects will view a series of faces, displaying either a neutral, fearful or angry expression, while the eye gaze of each face will be parametrically modulated. Subjects will be required to determine whether the gaze is directed towards them, or to the left or right, enabling us to measure individual sensitivity to gaze direction (cone of gaze) across different expressions. Individual measures in anxiety, BAS (reward sensitivity) and social anxiety will also be taken.
The visiting student will be provided with the relevant background literature enabling them to be actively involved in the design, implementation and analysis of the study. They will be expected to participate in E1 group meetings as well as emotion group meetings, and will have the opportunity to present their results to other members of the group. The student will also be expected to write up a methods and results section, giving them an understanding of the processes involved in composing journal articles. It is our intention that this project will enable the student to develop both an understanding of the relevant literature, as well as experience of the scientific process. This work will form an integral part of the ongoing research being carried out in the E1 group.
4) Visual short-term memory and intelligence
Rhodri Cusack
We only attend to a small part of the visual environment at any one time, yet we are able to form a bigger picture of what is around us. How do we combine the small parts together to form a stable representation at a larger scale? The answer is a robust form of memory, called "visual short-term memory" (VSTM) that allows us to accurately maintain a few objects for seconds or minutes while the scene is interpreted.
It has been influentially claimed that the limit of capacity of VSTM is determined by a central limit that restricts not just how many visual objects we can remember, but also how many items we can remember while we perform the complex mental operations required for intelligence tests and other measures of cognitive aptitude such as scholastic performance. These claims have been made on the basis of the finding that across different people, there is a clear correlation between individual differences in VSTM & intelligence.
However, recent work from our laboratory has shown that while some measures of VSTM (like those used previously) correlate with performance on intelligence tests, other good measures of VSTM do not. This suggests that some other factor contaminates performance on classic VSTM tasks, and it is this other contaminating factor that correlates with intelligence, not VSTM itself.
The aim of this project is to understand this critical contaminating factor. Two initial experiments will test whether the strategy used to encode visual information varies with intelligence, studying specifically the degree to which resources are focussed on a few of the items to be remembered versus distributed across all of them. The first experiment to be conducted by the post-holder will evaluate two ways of manipulating strategy: through instruction (while keeping the task matched); and by changing the task. In a second experiment, the most effective manipulation will be run on a wider group of volunteers varying broadly in intelligence.
The post-holder will recruit and test participants from the CBU volunteer panel. The experiments will be implemented by modifying existing programs, and some experience in programming would be advantageous but not essential. The post-holder will read background material and contribute to the experimental design where appropriate. The key experience gained will be a basic grounding in the cognitive neuroscience of visual short-term memory, and in the design and implementation of experiments to investigate it. If it suited the candidate's interests, it might be possible to include an FMRI neuroimaging component.
Please contact rhodri.cusack@mrc-cbu.cam.ac.uk if you would like to informally discuss this project.
5) Proposal for summer placement project "Optimal stimulus selection for neuroimaging experiments on semantic word variables"
Olaf Hauk, Friedemann Pulvermüller
Reading and word recognition are affected by a large number of psycholinguistic variables which are highly intercorrelated. Knowledge of this intercorrelation pattern and ways of dealing with it are crucial for successful neuroscientific research into language. In this summer project, the student would analyse a large stimulus set with respect to its suitability for factorial and parametric experimental designs. This would involve the use, for example, of recent methodological developments for stimulus selection at the CBU ("Mix&Match tools" by Maarten van Casteren). A particularly important question for our future research is: How many psycholinguistic variables, each tapping into a different psycholinguistic process, can be implemented in a single experiment, using factorial and parametric designs?
The student would be made familiar with the basic concepts of factorial and parametric experimental designs. He/she would learn how to use psycholinguistic databases, and how to analyse results with respect to matching and intercorrelation of variables. The project might also involve obtaining rating scores for a subset of stimuli (e.g. famiarity, imageability, action-relatedness etc.), which would offer the student experience with experimental psycholinguistic work. He/she will also be given the unique opportunity to assist in data acquisition in EEG/MEG/fMRI experiments.
We would like to give the student the opportunity to develop their own ideas, but we hope that their work will mainly benefit further EEG/MEG and fMRI experiments semantic word categories. For example, in one of our next experiments we would like to present action-words (and possibly words from other semantic categories) subliminally using a masked priming paradigm. The results might clarify whether previously reported somatotopic activation to different types of action-words ("pick-kick-lick") requires conscious perception of the word, or can be elicited without explicit attention directed towards the meaning of visually presented words.
The work of the summer student would involve working with Excel spread sheets, text files, searching databases, internet searches, contacting volunteers by phone and e-mail, possibly running simple behavioural experiments and possibly subject preparation and data acquisition in neuroimaging experiments under supervision.
6)Individual differences in rhythm perception (to commence after July 7th)
Jessica Grahn
While tapping to the beat in musical rhythm feels like a natural activity to most of us, there are several anecdotal reports of people who can't 'feel the beat'. The proposed project will investigate individual differences in rhythmic ability and how humans find a beat in rhythm. No musical background is required (though it may be helpful)
The goal of the project is to examine how individuals perform on simple rhythm tasks, comparing auditorily versus visually presented rhythms. One goal of the project is to examine how performance on auditory timing tasks influences subsequent visual rhythm perception. Another goal is to look at how rhythm perception is influenced by music or dance experience. It is hoped that we can select some participants for MRI testing based on their suitability and performance on the behavioural rhythm tasks
The student role involves recruiting and behavioural testing of musicians and non-musicians, analysing data on a computer (with supervision), and helping prepare the data for publication. The student would engage in introductory reading and discussions about rhythm perception and the regions of the brain that are involved in rhythm processing. He or she will also learn about experimental design considerations, informed consent and related ethical issues, behavioural testing procedures, and statistical techniques for data analysis. There will be opportunities to observe MRI scanning experiments.