Regional cerebral correlates of global motion perception - Evidence from unilateral cerebral brain damage

The used a psychophysical task to measure sensitivity to motion direction i n 50 stroke patients with unilateral brain lesions and 85 control subjects. Subjects were asked to discriminate the overall direction of motion in dyn amic stochastic random dot displays in which only a variable proportion of the spots moved in a single direction while the remainder moved randomly, B ehavioural and neurophysiological evidence shows that the middle temporal ( MT/V5) and middle superior temporal (MST) areas in the macaque monkey are i ndispensably involved in the perception of this type of motion, In human su bjects too, lesions in the same region disrupt performance on this task. He re we assessed more extensively the correlation between direction sensitivi ty for global motion and the anatomical locus of the lesion, Thresholds for perceiving the direction of global motion were impaired in the visual fiel d contralateral to the lesion in patients with lesions in the occipitoparie tal and parietotemporal areas involving the human analogue of areas MT/V5 a nd MST, but not by lesions in the occipito-temporal or anterior frontal are as, Patients with lesions involving the anterior temporal or parietal lobes displayed poor performance for stimuli presented in either visual field, w hich is consistent with the large and bilateral receptive fields in these a reas in monkeys. The perception of global motion was also more impaired in the centripetal than the centrifugal direction in the hemifield contralater al to the MT/V5 lesion. Surprisingly, thresholds were normal in all patient s when the displays contained static but not dynamic visual noise, suggesti ng that their deficit reflects an inability to filter out dynamic noise, Al though frequent repeated testing of some patients whose lesion involved the human homologue of MT was accompanied by an improvement in performance, th is was no greater than in other patients who received training on different motion tasks.