TARGET ANTICIPATION AND IMPAIRMENT OF SMOOTH-PURSUIT EYE-MOVEMENTS INSCHIZOPHRENIA

A reduced gain of smooth pursuit eye velocity has frequently been repo rted in schizophrenic patients. With respect to predictable stimuli, t his could be due to a deficit in predicting the target path. To determ ine this contribution to smooth pursuit eye movement performance, we a nalyzed the ocular smooth pursuit response to a sinusoidally moving ta rget that was suddenly stopped after some cycles of regular movement. Horizontal eye movements were recorded with infrared reflection oculog raphy in a group of 17 schizophrenic in-patients and 16 age-matched he althy subjects for controls. The patients exhibited a reduced gain of smooth pursuit velocity, but phase lag was not different from the cont rol group. After the unpredictable stop of target movement, predictive sinusoidal smooth pursuit was maintained for 150 to 200 ms in both gr oups. The resulting maximal position and velocity error was larger in the patient group. In conclusion: schizophrenic patients were able to generate a normal anticipatory component of smooth pursuit and to swit ch it off in response to external demands. They showed, however, an in creased velocity of anticipatory pursuit, which might be used to compe nsate for the primary deficit of smooth pursuit velocity frequently fo und in schizophrenics.