RETINOTOPIC AND DIRECTIONAL DEFECTS IN MOTION DISCRIMINATION IN HUMANS WITH CEREBRAL-LESIONS

We investigated the discrimination of motion direction in peripheral and central vision in 23 patients with unilateral cerebral hemispheric lesions on computed tomography or magnetic resonance imaging. We used random dot cinematograms that determined a percent coherence motion threshold for 16 points in the peripheral field and for four directions separately in central vision. We measured asymmetry of right- versus left-field peripheral discrimination (retinotopic defects) and asymmetry of central discrimination for rightward versus leftward motion (directional defects), compared with normal subjects. Five patients had directional asymmetries of foveal motion perception, all worse for motion toward the side of their lesions. One patient had a bidirectional defect for the perception of horizontal motion. For 3 of these 6, the average of all horizontal and vertical motion discrimination thresholds was also elevated. Two had contralateral retinotopic defects. One of these also had an ipsidirectional foveal defect, but the other did not. The remaining 5 patients with ipsidirectional foveal defects had hemianopias that precluded testing for coexistent retinotopic defects. The lesions of the 6 patients with ipsidirectional defects overlapped in white matter underlying the lateral temporo-occipital cortex, at the junction of Brodmann areas 19 and 37. In contrast, lesions of patients without directional defects spared this region.