Irregular speech rate dissociates auditory cortical entrainment, evoked responses, and frontal alpha

Kayser, S. J., Ince, R. A. A. , Gross, J. and Kayser, C. (2015) Irregular speech rate dissociates auditory cortical entrainment, evoked responses, and frontal alpha. Journal of Neuroscience, 35(44), pp. 14691-14701. (doi: 10.1523/JNEUROSCI.2243-15.2015) (PMID:26538641) (PMCID:PMC4635123)

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The entrainment of slow rhythmic auditory cortical activity to the temporal regularities in speech is considered to be a central mechanism underlying auditory perception. Previous work has shown that entrainment is reduced when the quality of the acoustic input is degraded, but has also linked rhythmic activity at similar time scales to the encoding of temporal expectations. To understand these bottom-up and top-down contributions to rhythmic entrainment, we manipulated the temporal predictive structure of speech by parametrically altering the distribution of pauses between syllables or words, thereby rendering the local speech rate irregular while preserving intelligibility and the envelope fluctuations of the acoustic signal. Recording EEG activity in human participants, we found that this manipulation did not alter neural processes reflecting the encoding of individual sound transients, such as evoked potentials. However, the manipulation significantly reduced the fidelity of auditory delta (but not theta) band entrainment to the speech envelope. It also reduced left frontal alpha power and this alpha reduction was predictive of the reduced delta entrainment across participants. Our results show that rhythmic auditory entrainment in delta and theta bands reflect functionally distinct processes. Furthermore, they reveal that delta entrainment is under top-down control and likely reflects prefrontal processes that are sensitive to acoustical regularities rather than the bottom-up encoding of acoustic features.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Kayser, Professor Christoph and Gross, Professor Joachim and Kayser, Dr Stephanie and Ince, Dr Robin
Authors: Kayser, S. J., Ince, R. A. A., Gross, J., and Kayser, C.
College/School:College of Medical Veterinary and Life Sciences > School of Psychology & Neuroscience
Journal Name:Journal of Neuroscience
Publisher:Society for Neuroscience
ISSN (Online):1529-2401
Copyright Holders:Copyright © 2015 Kayser et al.
First Published:First published in Journal of Neuroscience 34(44):14691-14701
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
658701Pathways and mechanisms underlying the visual enhancement of hearing in challenging environments.Christoph KayserBiotechnology and Biological Sciences Research Council (BBSRC)BB/L027534/1INP - CENTRE FOR COGNITIVE NEUROIMAGING
597051Natural and modulated neural communication: State-dependent decoding and driving of human Brain Oscillations.Joachim GrossWellcome Trust (WELLCOME)098433/Z/12/ZINP - CENTRE FOR COGNITIVE NEUROIMAGING