Cerebellar lesions impair rapid saccade amplitude adaptation

This study investigated whether the cerebellum is essential for rapid sacca de adaptation. Saccade adaptation was elicited by 30% backward target steps during the primary saccade. Patients with cerebellar lesions adapted less than normal subjects, but saccade adaptation was most impaired in the group of patients with cerebellar degeneration. As the variability of the saccad e gain in patients with cerebellar degeneration did not significantly diffe r from that in the other patients, the increased variability in motor perfo rmance due to a cerebellar lesion cannot alone explain this impaired adapta tion.