The long term goal of this research is to understand the neural substrates of certain forms of complex visual behavior and other higher cortical functions. To this end, the proposed studies will examine the functional organization of the superior temporal polysensory area (STP) in the superior temporal sulcus (STS) of the rhesus monkey. The STP area is likely to be homologous to human brain regions subserving complex visuospatial functions and directed attention. In humans, damage to homologous cortical areas causes devastating symptoms such as hemineglect. Both neuroanatomical and physiological studies indicate that STP cortex corresponds largely to architectonic area TPO and contains distinct subdivisions, [suggesting functional specialization within STP]. As a starting point for analysis of the different contributions of STP subdivisions to visual function, the proposed experiments will examine the relationship of STP areas to the dorsal and ventral cortical visual streams, associated with motion and form processing, respectively. Two sets of combined morphological- physiological experiments are proposed. The first strategy will examine the differential connections of subdivisions of area TPO with better known, and functionally different, eye movement related portions of the frontal lobe. Microstimulation mapping will be used to identify [the frontal eye field, supplemental eye field, and the frontal ventral area; then different anterograde tracers will be injected into 2-3 different, physiologically defined sites.] Laminar and areal termination patterns will identify separate areas within STP cortex, and show which STP areas relate to subsystems of the dorsal visual stream concerned with directing eye movements. Comparison in the same hemisphere of projections from the [2-3] frontal areas will provide important information on how different eye movement related inputs are integrated within STP cortex. The second strategy will be to identify physiological zones within rSTP, inject them with tracers, and then to study the cortical and subcortical (pulvinar) connections and architectonic characteristics of functionally defined sites. These experiments will provide the first direct correlations of physiologically defined rSTP with the morphology of STP cortex, and place the injected zones within the model framework of dorsal, ventral, or both streams of visual processing. Together, these studies will elucidate possible specialization of different STP areas for visuospatial or polysensory integration.
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