PRESERVED LEFTWARD MOVEMENT IN LEFT UNILATERAL SPATIAL NEGLECT DUE TOFRONTAL LESIONS

Three patients with left unilateral spatial neglect after predominantl y frontal lobe lesions were asked to extend a horizontal line leftward s to double its original length. In this line extension task, they rea dily executed movements in or towards the contralesional left space. T hey performed the task in the left and right hemispaces as well as in the midline. The mean extension lengths did not differ significantly a mong these three spatial conditions. These results suggest that direct ional hypokinesia takes little part in left unilateral spatial neglect due to frontal lobe lesions. It is considered that the patients could execute leftward movements as the task oriented their attention suffi ciently to the left. Two of the three patients, like reported cases wi th frontal neglect, showed a typical exploratory deficit for the left space in the line cancellation test. Such a deficit found in the tradi tional tasks, however, does not mean the presence of directional hypok inesia. Ah three patients showed visual extinction on double simultane ous stimulation. An attentional mechanism seems to play a predominant part in unilateral spatial neglect due to frontal lesions.