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Cortical correlates of speech intelligibility measured using functional near-infrared spectroscopy (fNIRS)

Lawrence, Rachael J.; Wiggins, Ian M.; Anderson, Carly A.; Davies-Thompson, Jodie; Hartley, Douglas E.H.

Authors

Rachael J. Lawrence rachael.lawrence@nottingham.ac.uk

Carly A. Anderson

Jodie Davies-Thompson



Abstract

Functional neuroimaging has identified that the temporal, frontal and parietal cortex support core aspects of speech processing. An objective measure of speech intelligibility based on cortical activation in these brain regions would be extremely useful to speech communication and hearing device applications. In the current study, we used noise-vocoded speech to examine cortical correlates of speech intelligibility in normally-hearing listeners using functional near-infrared spectroscopy (fNIRS), a non-invasive, neuroimaging technique that is fully-compatible with hearing devices, including cochlear implants. In twenty-three normally-hearing adults we measured (1) activation in superior temporal, inferior frontal and inferior parietal cortex bilaterally and (2) behavioural speech intelligibility. Listeners heard noise-vocoded sentences targeting five equally spaced levels of intelligibility between 0 and 100% correct. Activation in superior temporal regions increased linearly with intelligibility. This relationship appears to have been driven in part by changing acoustic properties across stimulation conditions, rather than solely by intelligibility per se. Superior temporal activation was also predictive of individual differences in intelligibility in a challenging listening condition. Beyond superior temporal cortex, we identified regions in which activation varied non-linearly with intelligibility. For example, in left inferior frontal cortex, activation peaked in response to heavily degraded, yet still somewhat intelligible, speech. Activation in this region was linearly related to response time on a simultaneous behavioural task, suggesting it may contribute to decision making. Our results indicate that fNIRS has the potential to provide an objective measure of speech intelligibility in normally-hearing listeners. Should these results be found to apply similarly in the case of individuals listening through a cochlear implant, fNIRS would demonstrate potential for a clinically useful measure not only of speech intelligibility, but also of listening effort.

Journal Article Type Article
Publication Date Dec 28, 2018
Journal Hearing Research
Print ISSN 0378-5955
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 370
Pages 53-64
APA6 Citation Lawrence, R. J., Wiggins, I. M., Anderson, C. A., Davies-Thompson, J., & Hartley, D. E. (2018). Cortical correlates of speech intelligibility measured using functional near-infrared spectroscopy (fNIRS). Hearing Research, 370, 53-64. doi:10.1016/j.heares.2018.09.005
DOI https://doi.org/10.1016/j.heares.2018.09.005
Keywords Sensory Systems; Auditory cortex; Functional near-infrared spectroscopy; Neuroimaging; Speech comprehension; fNIRS
Additional Information This article is maintained by: Elsevier; Article Title: Cortical correlates of speech intelligibility measured using functional near-infrared spectroscopy (fNIRS); Journal Title: Hearing Research; CrossRef DOI link to publisher maintained version: https://doi.org/10.1016/j.heares.2018.09.005; Content Type: article; Copyright: Crown Copyright © 2018 Published by Elsevier B.V.
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