Further analysis of the control of voluntary saccadic eye movements in schizophrenic patients.

Many schizophrenic patients reveal abnormalities in the antisaccade task. To better understand the nature of these abnormalities, in the present study we have assigned to schizophrenics the no-saccade task (subjects were required to remain fixated without being disturbed by a reflexive saccade) and memory-saccade task (subjects were required to look at a remembered target) in addition to the antisaccade and saccade tasks used previously. Many schizophrenics revealed higher error rates in the no-saccade task, and latencies of saccades to a memorized target were significantly longer than controls in the memory-saccade task. Peak velocities of saccades of large amplitudes in the memory-saccade and antisaccade tasks (but not in the saccade task) were significantly slower and durations of such saccades were longer than normal controls despite the similarity between the distributions of amplitudes of such saccades between the patients and controls. These results suggest that many schizophrenics have difficulty suppressing reflexive saccades and initiating and executing appropriate volitional saccades when the goal for the movements is known but not visible.