The long-term goal of this research is to understand the neural substrates underlying certain forms of complex visual behavior and other higher cortical functions. To this end, a combined anatomical and physiological approach will be used to study multimodal sensory cortex in the superior temporal sulcus (STS) of the rhesus monkey. This region, termed the Superior Temporal Polymodal area (STP), contains cells that respond predominantly to visual, but also to somatic sensory and auditory, stimuli as well as to stimulfation in more than one sensory modality. Anatomical studies gave shown that cortex in the region of STP receives converging inputs from visual, somatic sensory, and auditory areas. Since it is likely to be homologous to areas of the human brain that subsetve such functions as visuospatial ability, language, and directed attention, an analysis of STP cortex in monkeys may contribute to understanding their neural bases. Disruption of these areas by focal or diffuse disease cause devastating symptoms such as visual agnosia, aphasia, and neglect. Anatomical studies have parcellated the STP region into several cytoarchitectonic/connectional areas. More recent studies suggest that one of these, architectonic area TPO, can be further subdivided into four different interconnecting units along the rostrocaudal axis of the STS. Caudal sectors of area TPO have markedly different extrinsic connections from those of rostral TPO. This suggests possible funcrional differences betwen rostral and caudal divisions, As a first step toward understanding the funcrional organization of the STP region, therefore, the proposed studies will determine the location, extent, and internal organization of the caudal subregion cSTP. Neurophysiological mapping techniques will be used to examine clustering of unimodal and multimodal responses within cSTP and its overall visual and somatosensory topography, and to identify physiological distinctions from adjoining areas of cortex. The physiological demarcations within the STS will be compared with patterns of cortical cyto-and myeloarchitectonics. In the same experiments, conventional neuroanatomical tracers will be injected into physiologically identified sites in cSTP, and the relationship of response clusters to patterns of intrinsic and extrinsic cortical connections will be examined.
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