Identifying acoustic-level and language-specific sensory processing mechanisms

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Speech perception is modulated by experiences with native language phonotactic patterns. Sensory processing of speech is fundamental to perception, language learning, and language comprehension however much is unknown about how neural signals become language-specific within the cortical information stream. Preliminary evidence suggests that language experience with phonotactic patterns modulates acoustic-level sensory processing at early cortical stages (<150 ms) through feedback within the low frequency bands of the electroencephalogram (EEG). However, there are conflicting reports on the timing of the modulatory effects, and few, if any, cross-linguistic investigations of native and non-native phonotactic patterns that examine the direction of information flow within cortical networks. For this project, we will analyze 96 EEG datasets, previously obtained from 24 native Polish and 24 native English-speaking adults as they listened to same and different spoken nonword pairs during two listening conditions, an Attend and Passive condition. Nonwords within the pairs contained the onset sequences /pt/, /pət/, /st/, and /sət/ that occur in the Polish and English languages, except for /pt/, which never occurs in English in the word onset position. Analysis of this dataset will test the hypothesis that language-specific sensory processing occurs early within the cortical information stream (<150 ms) through information flow directed to phonological processing regions in auditory cortex. Multiple methods of analysis including AEPs, measures of time-frequency from brain source-level channels, current source density, and measures of brain connectivity, including coherence and Granger causality-based connectivity will be used to carry out the specific aims. Aim 1 will determine whether sensory processing of spoken nonwords is language-specific within the context of selective attention at early cortical stages. Aim 2 will evaluate whether sensory processing of spoken nonwords is language-specific within the context of repeated phonological sequences at early cortical stages. Aim 3 will determine the spatial distribution of language-specific activity and the direction of information flow during sensory processing of native and non- native phonotactic patterns and within the contexts of attention and repetition suppression. The outcomes will clarify sensory processing mechanisms of speech perception.