Recent work supports a novel, predictive coding account of the cortical computations supporting speech perception and comprehension. Predictive mechanisms have been implicated in the optimal integration of prior knowledge with degraded speech signals (Sohoglu, et al., 2012; Wild et al., 2012). Furthermore, the time-course of STG responses during identification of newly-consolidated spoken words (e.g. formubo), and familiar/unfamiliar lexical neighbours (formula/formuti) is uniquely consistent with predictive coding (Gagnepain, Henson & Davis, 2012). In addition to lexical and phonological predictions that shape recognition of single words, we have argued for oscillatory neural processes that entrain to regular amplitude modulations in intelligible speech (Peelle et al., in press). These oscillatory processes may explain a range of perceptual phenomena indicative of rate dependence in spoken sentence comprehension (Peelle & Davis, 2012). We have used source localization to show good anatomical correspondence between neural generators of oscillations observed in MEG (Peelle et al., in press) and previous fMRI work which localised neural responses that correlate with sentence intelligibility to lateral temporal and frontal systems (Davis & Johnsrude, 2003; Davis et al., 2011).

Relevant publications

Davis, M.H. & Johnsrude, I. S. (2003) Hierarchical processing in spoken language comprehension. Journal of Neuroscience, 23(8), 3423-3431

Davis, M. H., Ford, M. A., Kherif, F., Johnsrude, I. S. (2011) Does semantic context benefit speech understanding through “top-down” processes? Evidence from time-resolved sparse fMRI. Journal of Cognitive Neuroscience, 23(12), 3914-3932.

Gagnepain, P., Henson, R.N., Davis, M.H. (2012) Temporal predictive codes for spoken words in human auditory cortex. Current Biology, 22(7), 615-621.

Peelle, J.E., Davis, M.H. (2012) Neural oscillations carry speech rhythm through to comprehension. Frontiers in Psychology, 3, 320.

Peelle, J., Gross, J., Davis, M.H. (in press) Phase-locked responses to speech in human auditory cortex are enhanced during comprehension. Cerebral Cortex

Sohoglu, E., Peelle, J.E., Carlyon, R.P., Davis, M.H. (2012) Predictive top-down intergration of prior knowledge during speech perception. Journal of Neuroscience, 32(25), 8443-8453.

Wild, C., Davis, M.H., Johnsrude, I.S. (2012) The perceptual clarity of speech modulates activity in primary auditory cortex: fMRI evidence of interactive processes in speech perception. NeuroImage, 60, 1490-1502.

One focus of research with Jenni Rodd (UCL) and others concerns resolving ambiguity in the form and meaning of spoken language. We’ve compared fMRI responses to high and low ambiguity sentence; showing that a frontal and temporal lobe network is involved in selecting the right meaning for words like bark or bank in spoken sentences (Rodd et al., 2005). This fMRI method provides a neural marker for hidden comprehension in vegetative patients (Coleman et al., 2009) and during sedation/anaesthesia (Davis et al., 2007). In more recent work, we have used a dual-task method to show that ambiguity resolution places a significant load on domain general frontal processes (Rodd et al, 2010), and that these processes also contribute to the appreciation of puns (Bekinschtein et al., 2011). We’ve further used a fast fMRI method to distinguish activation in response to ambiguous words from later responses contributing to disambiguation (Rodd et al., 2012). Neural processes linked to ambiguity resolution are further associated with long-lasting changes to meaning preferences for ambiguous words (Rodd et al., in press).

Relevant publications

Bekinschtein, T., Davis, M.H., Rodd, J.M., Owen, A.M. (2011) Why clowns taste funny: the relationship between humour and semantic ambiguity. Journal of Neuroscience 31(26), 9665-9671.

Coleman, M.R., Davis, M.H., Rodd J.M., Robson T., Ali A., Pickard J.D., Owen A,M. (2009) Towards the routine use of brain imaging to aid the clinical diagnosis of disorders of consciousness. Brain, 132, 2541-2552.

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.

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.

Rodd, J.M., Johnsrude, I.S. and Davis, M.H. (2012) Dissociating frontotemporal contributions to semantic ambiguity resolution in spoken sentences. Cerebral Cortex, 22(8), 1761-1773

Rodd, J.M., Lopez Cutin, B., Millar, A., Kirsh, H. and Davis, M.H. (in press) Long-term priming of the meanings of ambiguous words: Evidence for the top-down influence of sentential context on semantic representations. Journal of Memory and Language

An important focus of research over the last several years has been to understand how cognitive and neural interactions between perceptual and linguistic processes endow human speech perception with unmatched tolerance for background noise, intrinsic variability and extreme degradation in everyday listening (see Mattys, Davis, Bradlow & Scott, 2012, for a review). In laboratory studies, we have characterised processes of top-down perceptual adaptation to simulations of speech transduced by a cochlear implant (vocoded speech, cf. Davis et al., 2005; Hervais-Adelman et al., 2008; 2011). These effortful processes are associated with elevated activity in frontal and motor regions (Hervais-Adelman, et al, 2012; Wild et al., 2012), and plausibly linked to top-down predictive mechanisms (Sohoglu et al., 2012; Davis & Johnsrude, 2007).

Relevant publications

Davis, M.H., Johnsrude, I.S., Hervais-Adelman, A., Taylor, K. & McGettigan, C.M. (2005) Lexical information drives perceptual learning of distorted speech: Evidence from the comprehension of noise-vocoded sentences. Journal of Experimental Psychology: General, 134(2), 222-241

Davis, M.H., Johnsrude, I.S. (2007) Hearing speech sounds: Top-down influences on the interface between audition and speech perception. Hearing Research, 229(1-2), 132-147

Hervais-Adelman, A., Davis, M.H., Johnsrude, I.S., Carlyon, R.P (2008) “Perceptual learning of noise vocoded words: effects of feedback and lexicality.” Journal of Experimental Psychology: Human Perception and Performance, 34(2), 460-474.

Hervais-Adelman, A., Davis, M.H., Taylor, K., Johnsrude, I.S., Carlyon, R.P (2011) Generalization of perceptual learning of vocoded speech: Evidence for abstract pre-lexical representations. Journal of Experimental Psychology: Human Perception and Performance, 37(1), 283-295.

Hervais-Adelman, A. G., Carlyon, R. P., Johnsrude, I. S., Davis, M. H. (2012) Brain regions recruited for effortful comprehension of noise-vocoded words: evidence from fMRI. Language & Cognitive Processes, 27(7/8), 1145-1166.

Mattys, S. Davis, M.H., Bradlow, A., Scott, S.K. (2012) Speech reception in adverse conditions: A review. Language and Cognitive Processes, 27(7/8), 953-978.

Sohoglu, E., Peelle, J.E., Carlyon, R.P., Davis, M.H. (2012) Predictive top-down intergration of prior knowledge during speech perception. Journal of Neuroscience, 32(25), 8443-8453.

Wild, C.J., Yusuf, A., Wilson, D., Peelle, J.E., Davis, M.H., Johnsrude, I.S. (2012) Effortful listening: The processing of unattended speech depends critically on its acoustic clarity. Journal of Neuroscience 32(40), 14010-14021

Processes of short-term neural adaptation have largely failed to demonstrate neural evidence for stable representations of new spoken words (cf. Orfanidou et al, 2006). Motivated by these findings, and by behavioural evidence for offline consolidation processes we have proposed a novel complementary systems account of word learning (Davis & Gaskell, 2009). This proposal is supported by studies of spoken word learning that highlight a hippocampal system that encodes novel items (Davis et al., 2009). Processes of overnight consolidation are then required for training-induced changes to cortical responses to be observed. It is only on the day after learning that neural responses to novel spoken words come to resemble responses for existing, familiar words (Davis et al., 2009; Gagnepain et al., 2012). Similar mechanisms for consolidation may also be required before competition occurs between newly-learned and established meanings of familiar words (Rodd et al., 2012). We have further shown that offline consolidation is required if representations of newly learned morphemes are to support generalization in speeded language tasks (Tamminen et al., 2012). Similar mechanisms of learning and generalization are critical for forming associations between written letters and speech sounds in reading acquisition. A meta-analysis of functional imaging studies of adult reading shows parallel neural pathways for componential and whole-word reading consistent with cognitive accounts (Taylor et al., 2012). We are currently comparing learning processes for object-name and letter-sound associations so as to assess how neural systems for associative learning contribute to acquiring a laboratory model of literacy.

Relevant publications

Davis, M.H., Di Betta, A., Macdonald, M.J.E., Gaskell, M.G. (2009) Learning and consolidation of novel spoken words. Journal of Cognitive Neuroscience, 21(4), 803-820.

Davis, M.H., Gaskell, M.G. (2009) A complementary systems account of word learning: neural and behavioural evidence. Philosophical Transactions of the Royal Society B: Biological Sciences, 364(1536), 3773-3800.

Orfanidou, E., Marslen-Wilson, W.D., Davis, M.H. (2006) Neural response suppression predicts repetition priming of spoken words and pseudowords Journal of Cognitive Neuroscience, 18(8), 1232-1257

Rodd, J.M., Berriman, R., Landau, M., Lee, T., Ho, C., Gaskell, M.G., Davis, M.H. (2012) Learning new meanings for old words: effects of semantic relatedness. Memory & Cognition, 40(7), 1095-1108.

Tamminen, J., Davis, M.H., Merkx, M., Rastle, K. (2012) The role of memory consolidation in generalisation of new linguistic information. Cognition, 125(1), 107-112.

Taylor, J.S.H, Rastle, K., Davis, M.H. (in press) Can cognitive models explain brain activation during single-word reading? A meta-analysis of 36 neuroimaging studies. Psychological Bulletin

Matt Davis – Programme Leader

Sam Evans – Career Development Fellowship

Viktoria Havas – Visting student

Ediz Sohoglu – MRC Centennial Fund

Joanne Taylor – MRC/ESRC Fellowship and Newnham College