Neurobiology of Auditory Language Perception

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We employ functional MRI and lesion methods to map cortical systems supporting the perception and comprehension of auditory language. The studies are theoretically guided on the broadest scale by our dorsal-ventral framework for the neural organization of language, which holds that the majority of computational systems supporting language comprehension (the ventral stream) are located in the temporal lobe. We target three broad computational systems: (1) phonological-level systems, (2) sentence-level systemss, and (3) lexical-semantic-level systems which are juxtaposed between, and interact with (1) & (2). Thus, the present proposal aims to map the large-scale landscape of language perception/comprehension systems. Aim 1: To map cortical regions supporting phonological-level processes, their interaction with lexical-semantic systems, and their relation to non-linguistic processes. A major goal is to distinguish systems supporting sublexical (segmental) and lexical (word) stages of phonological processing/representation. Experiments proposed in this section are guided by the following hypotheses, (i) Sublexical processes are computed on dorsal aspects of the superior temporal gyrus (STG) whereas lexical- level phonological processes involve ventral aspects of the STG. (ii)Neural structures in the posterior middle temporal gyrus (pMTG), interface lexical-phonological systems with widely distributed lexical- semantic networks, (iii)Phonological systems, both sublexical and lexical, are bilaterally organized, while the proposed phonological-semantic interface system is more left dominant. Aim 2: To map cortical regions supporting sentence-level processes, their interaction with lexical-semantic systems, and their interaction with non-linguistic processes. Experiments proposed in this section are guided by the following hypotheses, (i) Sentence-level processes involve fields in the anterior temporal lobe (ATL), and interacts with lexical- semantic networks via a posterior temporal lobe interface network, (ii)Processing phrasal prosody involves anterior portions of the STG, whereas syntactic processes involve more ventral anterior STS/MTG regions, (iii) Systems supporting the processing of phrasal prosody share neural territory with non-linguistic auditory processes (e.g..music), whereas syntactic processes are carried out in circumscribed and domain-specific brain regions.