Walsh & Hoyt: Motion Perception Deficits with Unilateral Cerebral Lesions

Unilateral lesions of extrastriate cortex cause more subtle abnormalities of motion perception than cerebral akinetopsia. There are reports of contralateral hemifield defects for speed discrimination, for detection of boundaries between regions with different motion, and for discrimination of direction from backgrounds of motion noise. As in L.M. and A.F., motion detection and contrast thresholds for motion direction are normal in patients with these deficits, and lesions are located in lateral temporo-occipital cortex or the inferior parietal lobule, but only on one side of the brain. Hemiakinetopsia may not be commonly detected because of masking of the motion-perception deficits by a homonymous hemianopia caused by damage to the optic radiations or striate cortex.