Catagorizing Parallel Human Auditory Pathways by Spatiotemporally Focused TMS

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DESCRIPTION (provided by applicant): The human brain interprets complex acoustic environments with astounding speed and ease. Although our understanding on the neuronal basis of sound processing has greatly advanced during the past decades, the parallel functional organization of cortical auditory pathways of the human brain is still elusive. This proposal aims to develop, test, and refine a new experimental approach for mapping parallel auditory pathways, by examining a theoretical model of dual pathways for spatial ("where") vs. identity ("what") of sound information. Our novel approach combines advanced spatiotemporal brain imaging techniques and behavioral measurements during transient non-invasive deactivation (i.e., "transient lesions") of individual regions of human auditory pathway. We will utilize anatomical and functional MRI, EEG, and magnetoencephalography (MEG) to identify the locations and time courses of brain activity during sound identification ("what") and localization ("where") tasks. Transcranial magnetic stimulation (TMS) will be utilized to modulate individual regions of auditory cortex that are activated during task performance. This will allow us to investigate whether spatiotemporally focused transient deactivations in the putative parallel auditory pathways result in a double dissociation of behavioral effects. We will measure EEG simultaneously with TMS, to investigate modulation of auditory evoked responses by transient deactivation of different auditory cortex areas. The proposed studies will use advanced neuroimaging methods to study how the human brain processes auditory information. The spatiotemporally focused TMS approach applies anatomically and temporally focused interference pulses non-invasively and completely safely into the human brain. The anatomical and temporal foci of interference will be obtained from spatiotemporal brain imaging movies, based on combined fMRI/MEG/EEG. This multimodal approach allows us to test the specific behavioral effects of transient deactivation in the different foci of cortical auditory pathway, providing a unique way to verify theories suggested by animal models, human lesion studies, and neuroimaging research. Our research will lead to a better understanding of the neuronal pathways and circuits involved in the processing of sound information in the human brain. Although our current focus is in basic research, greater understanding of the neuronal basis of auditory perception may ultimately benefit investigation of hearing impairments and learning disabilities, as well as development of hearing aids and prosthetics. PUBLIC HEALTH RELEVANCE: We use advanced brain imaging and behavioral methods for mapping of parallel cortical auditory pathways in humans, by specifically testing a hypothesis of distinct "what" and "where" streams. This research may also advance investigation of various disorders with auditory abnormalities.