Smooth pursuit eye movement abnormalities in patients with schizophrenia and focal cortical lesions

Smooth pursuit eye movements have been widely used in clinical research in attempts to clarify the neural mechanism underlying various brain diseases. However, many of these studies are subject to two major weaknesses: a failure to control for neuropharmacological factors and an inadequately defined visual context against which the smooth pursuit tracking is measured. This paper addresses both of these issues in patients with schizophrenia or focal cortical lesions. In the first study we compared smooth pursuit eye movements in the dark in medicated and non-medicated patients fulfilling the DSM-IIIR criteria for schizophrenia, and a group of age-matched control subjects. Relative smooth pursuit eye velocity (i.e. gain) was reduced in both schizophrenic groups; however the effect was significantly greater in the neuroleptically medicated group. In the second study smooth pursuit, with and without a structured background, was compared in patients with discrete cortical lesions and normal subjects. The analysis revealed a cohort of patients manifesting a large inhibitory effect of a structured background on pursuit eye movements. Examination of CT scans showed that two regions are of particular importance in this effect: an area of parietal cortex lying within the architectonic boundaries of Brodmann's area 40 (Brodmann, 1909); and an area of white matter close to the lateral ventricles containing cortico-cortical connections. These data point strongly to the critical importance of neuropharmacological factors and the visual background conditions in studies of smooth pursuit eye movements