Joint Representation of Spatial and Phonetic Features in the Human Core Auditory Cortex

• Published in: Cell reports (Cambridge) Vol. 24; no. 8; pp. 2051 - 2062.e2
• Main Authors: Patel, Prachi, Long, Laura K., Herrero, Jose L., Mehta, Ashesh D., Mesgarani, Nima
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 21-08-2018
• Subjects: Acoustic Stimulation - methods; auditory cortex; Auditory Cortex - physiology; Auditory Perception - physiology; binaural sound; electrocorticography; Humans; Phonetics; sound localization; speech; electrocorticography; auditory cortex; binaural sound; sound localization; speech
• ISSN: 2211-1247; 2211-1247
• DOI: 10.1016/j.celrep.2018.07.076

The human auditory cortex simultaneously processes speech and determines the location of a speaker in space. Neuroimaging studies in humans have implicated core auditory areas in processing the spectrotemporal and the spatial content of sound; however, how these features are represented together is unclear. We recorded directly from human subjects implanted bilaterally with depth electrodes in core auditory areas as they listened to speech from different directions. We found local and joint selectivity to spatial and spectrotemporal speech features, where the spatial and spectrotemporal features are organized independently of each other. This representation enables successful decoding of both spatial and phonetic information. Furthermore, we found that the location of the speaker does not change the spectrotemporal tuning of the electrodes but, rather, modulates their mean response level. Our findings contribute to defining the functional organization of responses in the human auditory cortex, with implications for more accurate neurophysiological models of speech processing.
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•Direct recording from human auditory cortex reveals selectivity to speech direction•Spatial and spectrotemporal speech features are independently and jointly encoded•Neural population responses enable successful decoding of spatial and phonetic features•Speech direction modulates the mean neural response to spectrotemporal speech features
Using invasive recordings from the human core auditory cortex, Patel et al. show direct evidence for neural selectivity to the direction of the speaker relative to the listener. The direction of speech is jointly and independently represented with the speech phonetic features in the same region. Speech direction modulates the mean of the neural response to spectrotemporal features of speech.