PROJECT SUMMARY
Speech communication plays a crucial role in conveying our thoughts to others, maintaining social ties, and
supporting educational achievement. As a result, communication disorders that impact speech perception like
autism, dyslexia, and hearing loss can be costly to both individuals and society. Understanding the
neurobiological bases of speech processing is an important goal that has been hastened by invasive intracranial
electrophysiology in neurosurgical contexts. Yet, substantial behavioral evidence demonstrates dynamic, flexible
aspects of the mapping of speech input to phonemes that is not yet accounted for in neurobiological models.
This Exploratory/Developmental R21 project pursues the central hypothesis that listening context systematically
impacts cortical response to speech and therefore affects the diagnosticity of acoustic dimensions in signaling
phonemes. A newly established cross-disciplinary research team will use intracerebral recording via
stereoelectroencephalography (sEEG) obtained in a neurosurgical context to pursue this hypothesis. Like
electrocorticography (ECoG), sEEG offers high spatiotemporal resolution and can target the cortical surface,
including superior temporal gyrus (STG). Owing to the intracortical electrode placement, sEEG electrodes record
through the supratemporal plane, specifically targeting both deep sulcal and gyral grey matter including superior
temporal sulcus (STS) and Heschl’s gyrus (HG). Simultaneous scalp electroencephalography (EEG) will be
acquired to link these intracortical measures with noninvasive approaches appropriate in studies of healthy
listeners. Aim 1 will establish neural response to two acoustic-phonetic dimensions as a function of the perceptual
weight with which they signal phoneme identity. This will provide a baseline response for each participant for
comparison as experimental manipulations to listening context shift perceptual weights in Aim 2, and will
establish how individual differences in perceptual weighting strategies predict cortical electrophysiological
response. Aim 2 will introduce two well-established manipulations that, behaviorally, shift perceptual weights
relative to baseline: introduction of noise and introduction of an ‘accent’ for which the short-term speech input
deviates from distributional regularities of the native language. Examination of experimental manipulations
within-participant will provide a sensitive means by which to assay changes in neural response as a function of
changes in perceptual weights arising across listening contexts. Participants will be sampled across later
adolescence (15-25 years), a period during which perceptual weights provide informative heterogeneity. The
project will compound its impact by filling an important gap in understanding of speech processing, building a
bridge from invasive electrophysiological studies with patients to scalp EEG measures of human listeners
through combined sEEG+EEG, wedding classic and state-of-the-art computational approaches to inform
mechanisms, and delivering an understanding of the dynamic, flexible nature of speech processing with
substantial implications for communication disorders.