Direction and position factors in performance of line extension task by unilateral neglect subjects.

In this study was investigated the influence of direction and position in the performance of a line extension task by patients with unilateral neglect, with the aim of exploring the role of perceptual and premotor factors in this task. Twenty-three right brain damaged patients (14 patients with left unilateral neglect) were asked to extend horizontal lines both leftward and rightward; lines were presented in three different positions (left, right and central). Patients with neglect significantly overextended the lines in all conditions, but particularly toward the sagittal mid plane of the body and leftward when the line was presented on the right. The global overextension seem to be related to concomitant hemianopsia. A crucial finding in neglect group was that left extensions reduced progressively on passing from right through central to left presentation, particularly in patients with lesions involving frontal regions or the basal ganglia. The last finding supports the hypothesis that left overextension does not exclude the coexistence of both perceptual and premotor factors (causing directional hypometria) in left unilateral neglect.