The focus of the proposed studies is upon analyzing the anatomical substrates of visual and oculomotor processing in striatum. Striatum is strongly implicated in visuomotor integration by evidence that it participates in sequencing complex volitional behaviors, and by specific evidence showing (i) extensive and specific interconnections with visual and oculomotor areas, (ii) striatal and nigral cells may discharge selectively preceding purposive saccades, and (iii) eye movement disorders are characteristic of basal ganglia disease. The striatum also exhibits a complex intrinsic organization consisting of a lattice-like arrangement of histochemically specific compartments which appear to form both the basis for integration within striatum and for segregation of its input-output connections. The proposed studies will employ direct electrophysiological mapping for visual representation, and intracranial microstimulation mapping for eye movement representation, combined with immunohistochemical methods to demonstrate striatal compartments, and anterograde and retrograde tracer methods to demonstrate striatal connections. The following specific aims will be addressed: (1) Determine how electrophysiologically defined representations of visual space are related to the immunohistochemical compartments of striatum; (2) Determine how representations of eye movement are related to immunohistochemically defined striatal compartments; (3) Determine whether interdigitation or overlap occurs between contiguous functionally defined visual and eye movement compartments in striatum: (4) Determine how the segregated output pathways which arise within striatum are related to specific electrophysiologically defined compartments and to immunohistochemically defined compartments. Successful execution of the specific aims of the project will shed new light on the specific contributions of striatum to oculomotor control, upon the details of neuronal circuitry which link visual areas with oculomotor structures via striatum, and upon the fundamental principles by which brain employs visual information for initiation and guidance of voluntary movement. The long term health related consequences of this work is expected to be an improvement in the methods for diagnosis and treatment of debilitating oculomotor disorders and visuomotor apraxias.
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