Visuo-spatial neglect: qualitative differences and laterality of cerebral lesion.

From a large sample of patients who sustained a first stroke, 98 patients were selected with unilateral left brain damage and 92 with unilateral right brain damage. Examined on a visual search task (Star Cancellation) approximately four years after onset, we found a comparable incidence of visual inattention in the two groups. Despite this quantitative similarity, the qualitative pattern of performance was different in the two impaired samples. Patients with right brain damage showed a distinctive linear relationship whereby omission errors increased from right to left across the stimulus page. Within the left brain damaged sample, two subgroups could be discerned. As expected, one subgroup showed more contralesional than ipsilesional errors, but the other subgroup was comparable to the sample with right hemisphere damage. The reasons are discussed for these qualitative differences, drawing particular attention to the importance of motor/manual factors in the determination of performance on visual search tasks.