Smooth pursuit in schizophrenia: abnormalities of open- and closed-loop responses

A sample of 29 schizophrenia patients and 27 nonpsychiatric subjects were tested on measures of open- and closed-loop smooth-pursuit performance. Rashbass step-ramps were used to measure pursuit latency and open-loop gain. Regular ramps were used to calculate frequency and amplitude of both catch-up saccades and square-wave jerks, frequency of anticipatory saccades, and steady-state gain. Schizophrenia patients demonstrated lower open-loop gain than did nonpsychiatric subjects, an effect that was accentuated at faster target velocities. They also showed reduced steady-state gain, but only to 30 degrees/s right-moving targets. There was no evidence of saccadic abnormalities during smooth pursuit among the schizophrenia patients. These patients generated fewer square-wave jerks than did nonpsychiatric subjects for 10 degrees /s left-moving targets. These results suggest an abnormality of smooth-pursuit initiation among patients with schizophrenia.