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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Abstract
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 |
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Status: | Published |
Refereed: | Yes |
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: | 0270-6474 |
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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