CRCNS: Cortical representation of phonetic, syntactic and semantic information during speech perception and language comprehension

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The overarching goal of this project is to discover how language-related information is represented and processed in the human brain. To address this issue we propose to use a novel computational modeling approach, voxel-wise modeling. Voxel-wise modeling draws from the principles of nonlinear system identification, and it provides an efficient method for using complex data sets collected under naturalistic conditions to test multiple hypotheses about language representation. The specific research plan is divided into three aims, each targeted at a different form of language-related information. Aim 1 will reveal how low-level features of speech, such as spectral power, spectral modulation and phonemic structure, are represented across human cortex. Subjects will passively listen to human speech while hemodynamic brain activity is recorded by functional MRI. Voxel-wise modeling will then be used to determine how each point in the brain (i.e., each voxel, or volumetric pixel) is tuned for these various features. Using analogous methods, Aim 2 will reveal how syntactic and semantic features are represented across cortex. Finally, Aim 3 will reveal how language-related information is represented when it is delivered by auditory versus visual modalities. In this case speech and video stimuli will be used. Separate models will be estimated for data recorded during auditory and visual stimulation, and voxel-wise tuning will be compared across modalities. The voxel-wise computational models developed under this proposal will reveal how these various types of language-related information are represented across the cortical surface. These models will also provide clear predictions about how the brain will respond to novel speech stimuli. The results of the proposed research will have broad impacts on clinical problems related to speech perception and production, and they could form the basis of powerful brain decoding device that would enable neurological patients to communicate by thought alone.