Phonetic Feature Encoding in Human Superior Temporal Gyrus

TLDR

Speech perception extracts consonants and vowels from complex acoustic signals, yet the STG’s role in encoding phonetic information remains poorly understood. The study aimed to reveal how the STG represents the full English phonetic inventory using high‑density direct cortical recordings during natural speech listening. High‑density direct cortical surface recordings were employed while participants listened to natural continuous speech to map STG representations of the English phonetic inventory. Single electrodes showed selectivity to distinct phonetic features, with distributed population responses linking acoustic properties to spectrotemporal cues, some encoded nonlinearly or via cue integration, demonstrating the acoustic‑phonetic representation of speech in the human STG.

Abstract

During speech perception, linguistic elements such as consonants and vowels are extracted from a complex acoustic speech signal. The superior temporal gyrus (STG) participates in high-order auditory processing of speech, but how it encodes phonetic information is poorly understood. We used high-density direct cortical surface recordings in humans while they listened to natural, continuous speech to reveal the STG representation of the entire English phonetic inventory. At single electrodes, we found response selectivity to distinct phonetic features. Encoding of acoustic properties was mediated by a distributed population response. Phonetic features could be directly related to tuning for spectrotemporal acoustic cues, some of which were encoded in a nonlinear fashion or by integration of multiple cues. These findings demonstrate the acoustic-phonetic representation of speech in human STG.