Characteristics of remembered saccades in parkinson's disease

Abstract

Saccades to a remembered target use non-visual feedback and rely on a normal functioning of the projection from the caudate nucleus to the substantia nigra pars reticulata. The latter projection is known to be defective in Parkinson's disease and it seems therefore likely that remembered saccades are abnormal in such patients. In a series of three studies the characteristics of remembered saccades were compared with those of reflex saccades in patients with Parkinson's disease and normals. It was found that the remembered saccades of the patients were more hypometric than those of normals but that the final eye position was normal. Latency and peak velocity were normal as well. The patients exhibited an increased incidence of multistepping (“staircase saccades”). Using an inverse reconstruction technique, evidence was obtained for the presence of pulse doublets at the input of the oculomotor plant in such cases.