The goal of the proposed work is to investigate a large region of extrastriate visual cortex in the cat, the Clare-Bishop area. Its internal organization will be studied, and its relationship with three other areas of visual cortex, areas 17, 18, and 19. The Clare-Bishop area is of particular interest because it might be considered the """"""""highest-order"""""""" of the 3 visual areas that receive input from areas 17. Its response properties bear the least resemblence to those of area 17; it is unique in having major input from a zone of thalamus connected to the superior colliculus; and it receives only weak input from the lateral geniculate nucleus. The Clare-Bishop area appears to differ from areas 17, 18, and 19 in another fundamental way. Its map of the upper visual field is complex and redundant. It is logical to ask whether Clare- Bishop's map of the lower visual field is similarly organized. If it also is redundant, one might suspect that this kind of mapping is characteristic of higher-order visual cortex, and will be found in other areas. Almost nothing is known about other kinds of functional organization present in the Clare-Bishop area. Thus a major goal is to investigate whether it is compartmentalized according to particular response properties. Some possibilities are orientation preference, selectivity for stimulus distance, and selectivity for movement in depth. The third focus of this proposal concerns the ordering of connections between the Clare-Bishop area and primary visual cortex. In tracer experiments, labeled cells in area 17 that send axons to Clare-Bishop tend to be clustered. The functional basis of this clustering will be examined. It might relate to functional compartmentalization within the Clare-Bishop area, such that matching compartments in area 17 and Clare-Bishop are connected, while ones with opposite response properties are not. Alternatively, clustering might be an intrinsic characteristic of the cell population in area 17 projecting to the Clare-Bishop area. If so, it is possible that the regions lacking projections to Clare- Bishop send axons instead to either area 18 or area 19. If such regions are found, the possibility that they also have distinctive response properties will be examined.
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