Abstract
An antecedent potential (AP) and a positive spike (SP) potential that precede saccades have been described in normal human subjects using evoked potential techniques. These responses can be recorded over parietal cortex (P3, P4) with linked ear reference. The AP-SP was examined in two patients with progressive supranuclear palsy (PSP) and in two patients with congenital ocular motor apraxia. The response was grossly abnormal in both PSP patients and in one of the congenital ocular motor apraxia patients. This indicates that pre-saccadic cortical activity may be altered in these patients. Thus, these potentials may be of diagnostic value in the evaluation of supra-nuclear disorders of ocular motility.