title: Tracking cortical entrainment in neural activity: auditory processes in human temporal cortex.
abstract: A primary objective for cognitive neuroscience is to identify how features of the sensory environment are encoded in neural activity. Current auditory models of loudness perception can be used to make detailed predictions about the neural activity of the cortex as an individual listens to speech. We used two such models (loudness-sones and loudness-phons), varying in their psychophysiological realism, to predict the instantaneous loudness contours produced by 480 isolated words. These two sets of 480 contours were used to search for electrophysiological evidence of loudness processing in whole-brain recordings of electro- and magneto-encephalographic (EMEG) activity, recorded while subjects listened to the words. The technique identified a bilateral sequence of loudness processes, predicted by the more realistic loudness-sones model, that begin in auditory cortex at ~80 ms and subsequently reappear, tracking progressively down the superior temporal sulcus (STS) at lags from 230 to 330 ms. The technique was then extended to search for regions sensitive to the fundamental frequency (F0) of the voiced parts of the speech. It identified a bilateral F0 process in auditory cortex at a lag of ~90 ms, which was not followed by activity in STS. The results suggest that loudness information is being used to guide the analysis of the speech stream as it proceeds beyond auditory cortex down STS toward the temporal pole.
authors.affiliation: Neurolex Group, Department of Psychology, University of Cambridge Cambridge, UK ; MRC Cognition and Brain Sciences Unit Cambridge, UK.
authors.forename: Andrew
authors.initials: A
authors.lastname: Thwaites
authors.affiliation: MRC Cognition and Brain Sciences Unit Cambridge, UK.
authors.forename: Ian
authors.initials: I
authors.lastname: Nimmo-Smith
authors.affiliation: Neurolex Group, Department of Psychology, University of Cambridge Cambridge, UK ; MRC Cognition and Brain Sciences Unit Cambridge, UK.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Fonteneau
authors.affiliation: Department of Physiology, Development and Neuroscience, Centre for the Neural Basis of Hearing, University of Cambridge Cambridge, UK.
authors.forename: Roy D
authors.initials: RD
authors.lastname: Patterson
authors.affiliation: Department of Theoretical and Applied Linguistics, University of Cambridge Cambridge, UK.
authors.forename: Paula
authors.initials: P
authors.lastname: Buttery
authors.affiliation: Neurolex Group, Department of Psychology, University of Cambridge Cambridge, UK ; MRC Cognition and Brain Sciences Unit Cambridge, UK.
authors.forename: William D
authors.initials: WD
authors.lastname: Marslen-Wilson
keywords: MNE source space; fundamental frequency contour; information encoding; magnetoencephalography; model expression; neural computation; speech envelope