Primate auditory cortex is composed of areas grouped in regions at 3 levels in a hierarchical order of core-belt- parabelt, and each region subdivides into multiple areas anatomically and physiologically. Auditory information processing proceeds through levels and through areas within every level. Still higher level regions in the temporal, frontal and parietal lobes, and the cortical areas within them, are hypothesized to be more heavily specialized for higher cognitive processes. Studies of core and belt regions have characterized auditory properties like spectral tuning and have suggested functional segregation of anterior """"""""what"""""""" and posterior """"""""where"""""""" pathways of information processing. Though the parabelt region is anatomically known to differentiate into caudal and rostral parabelt areas, the region has been barely explored physiologically. Our BROAD OBJECTIVE is to characterize the properties and functions of the parabelt areas in primates. Cognitive processes involving parabelt region are expected to require auditory attention. Higher order cognitive inputs and auditory inputs are predicted to differ in terms of their cortical laminar activation pattern. In tis study, we use behavioral tasks that require attentive processing using auditory stimuli optimized for basic characterization, electrophysiological methods that discern different types of inputs, as well as functional connections between parabelt regions, and anatomical techniques to define the fine microcircuit structure of actual connections between these regions.
SPECIFIC AIM 1 is to characterize auditory response properties of parabelt neurons.
SPECIFIC AIM 2 is to characterize the routes and dynamics of signal flow through parabelt regions, as well as the fine structure of underlying anatomical connections. Parabelt regions in humans are implicated in not only acoustic perception but also complex functions like speech communication. Delineating the physiological properties and functional/structural interconnections of parabelt region during attentive auditory performance will advance our basic understanding of auditory perception mechanisms that are of direct relevance to neuropsychiatric and communication disorders in humans.
Parabelt region of auditory cortex is considered as a high hierarchical stage of speech communication processing, and yet unexplored. Delineation of its physiological properties and behavioral roles will enhance our understanding of the speech perception and the mechanisms of several mental cognitive disorders including autism and schizophrenia, as those disorders are related to neurological abnormalities in cortices including the parabelt.
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