1. Neuroscience
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Transformation of a temporal speech cue to a spatial neural code in human auditory cortex

  1. Neal P Fox
  2. Matthew Leonard
  3. Matthias J Sjerps
  4. Edward F Chang  Is a corresponding author
  1. University of California, San Francisco, United States
  2. Donders Institute for Brain, Cognition and Behaviour, Radboud University, Netherlands
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Cite this article as: eLife 2020;9:e53051 doi: 10.7554/eLife.53051

Abstract

In speech, listeners extract continuously-varying spectrotemporal cues from the acoustic signal to perceive discrete phonetic categories. Spectral cues are spatially encoded in the amplitude of responses in phonetically-tuned neural populations in auditory cortex. It remains unknown whether similar neurophysiological mechanisms encode temporal cues like voice-onset time (VOT), which distinguishes sounds like /b/-/p/. We used direct brain recordings in humans to investigate the neural encoding of temporal speech cues with a VOT continuum from /ba/ to /pa/. We found that distinct neural populations respond preferentially to VOTs from one phonetic category, and are also sensitive to sub-phonetic VOT differences within a population's preferred category. In a simple neural network model, simulated populations tuned to detect either temporal gaps or coincidences between spectral cues captured encoding patterns observed in real neural data. These results demonstrate that a spatial/amplitude neural code underlies the cortical representation of both spectral and temporal speech cues.

Article and author information

Author details

  1. Neal P Fox

    Neurological Surgery, University of California, San Francisco, San Francisco, United States
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0003-0298-3664
  2. Matthew Leonard

    Department of Neurological Surgery, University of California, San Francisco, San Francisco, United States
    Competing interests
    The authors declare that no competing interests exist.
  3. Matthias J Sjerps

    Centre for Cognitive Neuroimaging, Donders Institute for Brain, Cognition and Behaviour, Radboud University, Nijmegen, Netherlands
    Competing interests
    The authors declare that no competing interests exist.
  4. Edward F Chang

    Department of Neurological Surgery, University of California, San Francisco, San Francisco, United States
    For correspondence
    edward.chang@ucsf.edu
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0003-2480-4700

Funding

National Institutes of Health (R01-DC012379)

  • Edward F Chang

National Institutes of Health (F32-DC015966)

  • Neal P Fox

European Commission (FP7-623072)

  • Matthias J Sjerps

New York Stem Cell Foundation

  • Edward F Chang

William K. Bowes, Jr. Foundation

  • Edward F Chang

Howard Hughes Medical Institute

  • Edward F Chang

Shurl and Kay Curci Foundation

  • Edward F Chang

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Ethics

Human subjects: All participants gave their written informed consent before surgery and affirmed it at the start of each recording session. The study protocol was approved by the University of California, San Francisco Committee on Human Research. (Protocol number 10-03842: Task-evoked changes in the electrocorticogram in epilepsy patients undergoing invasive electrocorticography and cortical mapping for the surgical treatment of intractable seizures)

Reviewing Editor

  1. Jonathan Erik Peelle, Washington University in St. Louis, United States

Publication history

  1. Received: October 25, 2019
  2. Accepted: August 21, 2020
  3. Accepted Manuscript published: August 25, 2020 (version 1)
  4. Version of Record published: September 10, 2020 (version 2)

Copyright

© 2020, Fox et al.

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.

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