A lesion of cortical area V2 selectively impairs the perception of the direction of first-order visual motion.

Abstract

Lesions of area MT/V5 in monkeys and its presumed homologue, the motion area, in humans impair motion perception, including the discrimination of the direction of global motion in random dot kinematograms. Here we report the results of similar tests on patient TF, who has a discrete and very small, unilateral infarct in the medial superior part of the right occipital cortex. Structural MRI, co-registered in software with a standardized human brain atlas, reveals that the lesion involves area V2. The patient was impaired in his retinotopically corresponding left lower quadrant on several motion tasks including discrimination in random dot kinematograms of direction, speed and motion-defined discontinuity. He was also impaired on tasks selectively involving first-order motion based on luminance contrast but not on second-order motion based on texture contrast. The results show that even though area MT/V5 is intact, motion perception is abnormal and, in particular, his perception of first-order motion is impaired.