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

Fox, N. P., Leonard, M., Sjerps, M. J., & Chang, E. F. (2020). Transformation of a temporal speech cue to a spatial neural code in human auditory cortex. eLife, 9: e53051. doi:10.7554/eLife.53051.
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/ and/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.
Supplementary material
Data and code
Publication type
Journal article
Publication date
2020

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