Control of voluntary and reflexive saccades in Parkinson's disease.

Eight patients with idiopathic Parkinson's disease (PD) were compared with a group of age-matched controls on both reflexive saccade and antisaccade tasks. While reflexive, visually guided saccades led to equivalent performance in both groups, PD patients were slower, made more errors, and showed reduced gain on antisaccades (AS). This is consistent with previous results showing that PD patients have no difficulty with reflexive saccades but show deficiencies in a number of voluntary saccade paradigms. Moreover, visual information in the form of landmarks improves AS performance more for PD patients than controls, a finding analogous to results seen with other motor acts such as target-directed pointing. Results are discussed in terms of a two-process model of attention and eye movements.