The modification of saccade by an unilateral lesion of the anterior and posterior cerebrum

Abstract

Saccadic eye movements of patients with unilateral lesion of the cerebrum were quantitatively investigated. The subjects included twenty-seven patients with cerebrovascular accidents and four with brain tumor. The localization of the lesions was evaluated by CT scan and/or cerebral angiogram. Seventeen patients had lesions in the anterior cerebrum and ten in the posterior cerebrum. Saccadic eye movements were elicited by presenting a light spot in the right and left visual fields on the screen, five and ten degrees from the center and such were registered by an X-Y tracker. The amplitude and duration of the saccades as well as visual reaction time were measured. The predictive duration for 15 degrees saccade was obtained from the amplitude duration relationship in each patient.Duration of the saccade to the contralateral side of the lesion was longer than that to the ipsilateral side. However, the difference was statistically significant (p<0.05) only in the patients with lesions in the anterior cerebrum. The amplitude of the initial saccade to the contralateral side was significantly smaller (p<0.01) than that to the ipsilateral side regardless of the localization of the lesion. Visual reaction time for saccades showed no differences between the contralateral and ipsilateral sides. In only three of the twenty-seven patients was there an apparent slow saccade to the contralateral side.The characteristics of the saccade of the unilateral lesion in the cerebrum include : 1) Inaccuracy of the saccade which was usually hypometric, 2) Minimum slower saccade to the contralateral side in patients with lesions in the anterior cerebrum, and 3) No effect on visual oculomotor reaction time. The results suggest modulation of the saccade by the contralateral cerebrum.