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Hearing and Donuts (Brain and Bagels) Seminar
October 21, 2022 @ 8:30 am - 9:30 am
Nike Gnanateja, Ph.D.
Visiting Assistant Professor
Communication Sciences and Disorders
University of Wisconsin-Madison
Topic: Cortical Encoding of Discrete Prosodic Patterns in Continuous Speech
Prosodic patterns carry crucial information for disambiguating the linguistic and affective cues to convey a coherent structure of the talker’s intended message to the listener. These prosodic patterns provide important contextual cues and help bind information across different segmental speech units for efficient perception. Prior neuroimaging work using intracerebral recordings shows that diffuse sites in the superior temporal gyrus (STG) and middle temporal gyrus (MTG) encode intonational categories at sentential levels. However, the larger sentential level prosody consists of short timescale pitch inflections operating at pre-lexical levels tied to the stressed syllables that form discrete prosodic categories of pitch accents, and shift the attentional focus of a sentence and cue salience and contrastive information. These pitch accents are fundamental components of prosody in languages such as English. We leveraged the high spatio-temporal resolution of intracerebral recordings in 8(2 female) human participants to study the cortical encoding of pitch accents in continuous speech. Cortical activity at electrodes in the bilateral Heschl’s gyrus selectively represented the pitch accents. The encoding of the pitch accents could not be explained only by the spectrotemporal acoustic cues, suggesting a higher order abstract representation of the pitch accents in the brain. The representation of pitch accents showed spatial dissociation from the representation of segmental speech features along the superior temporal plane, suggesting distinct neural mechanisms underlying encoding of prosodic and phonetic speech features. The cortical locus of pitch accent processing in the hierarchically earlier regions is consistent with their pre-lexical role of forming attentional focus potentially facilitating subsequent lexical processing at higher levels in the system.