The basis of visual constructional disability in patients with unilateral cerebral lesions.

Patients with left and right unilateral hemispheric lesions were compared on the Form Assembly Task, a visual construction task requiring perceptual but not executive, motor, or verbal skills. Right lesioned patients were inferior to lefts and normals in both degree and frequency of impairment. Performances on the assembly task and two visual discrimination tasks were correlated among right but not left lesioned patients. Left lesioned patients took significantly longer to achieve maximum level of performance than either rights or normals. Neither sex nor duration of lesion affected Form Assembly performance. Results were consistent with the hypothesis that visual perceptual deficits underlie constructional difficulties among right but not left lesioned patients.