The top-down descending roles from higher cortical areas to lower areas is a big unsolved problem in systems neuroscience.In the visual system,the dorsal stream and the ventral stream are two the major parallel streams carrying and processing distinctly different types of motion and form information along the visual pathways in the cats and monkey brain.To study the functional effects of higher-order visual cortical area on the lower-order area in the visual information processing,we examined the influence of signals descending from cortical areas of 21a and the posteromedial lateral suprasylvian (PMLS) on the orientation and direction selectivity and their functional organization in cat area 17 revealed by intrinsic signal optical imaging combined with local drug application in 21a and PMLS.