A MOTION AREA IN HUMAN VISUAL-CORTEX

We have localized an area in the human brain involved in the processin g of contours defined by motion differences (kinetic contours) by comp aring with positron emission tomography the regional cerebral blood fl ow in tasks performed with kinetic and luminance defined gratings. The se tasks included passive viewing, counting the total number of gratin g stimuli, and counting the number of gratings of a given orientation. Comparison between the counting tasks and passive viewing with a give n type of contour revealed a set of active areas that were similar for both luminance-defined and kinetic contours. Comparisons between thes e two types of contours revealed a single focus in the right hemispher e that did not overlap with the many regions activated by uniform moti on. In particular this ''kinetic focus'' was clearly separated from th e area previously defined as the human homologue of V5/middle temporal . Activity in this kinetic focus was stronger when orientation had to be processed than in the other two tasks. These results and control ex periments with uniformly moving random dot patterns suggest the existe nce of an area in the human visual system that is activated much more by kinetic contours than by luminance contours or uniformly moving ran dom dots. Up to now, such an area has not been described in the monkey visual system.