SPEM impairment in drug-naive schizophrenic patients: evidence for a trait marker.

Smooth-pursuit eye movements (SPEM) were assessed in healthy subjects and in drug-naive, chronic, and residual schizophrenic patients. SPEM gain was found to be decreased in all the schizophrenic patients who also exhibited a significant increase in the rate of saccades. The frequency of square-wave jerks was the same in schizophrenic patients and normal controls, suggesting that the primary abnormality in schizophrenic patients was a low gain rather than a defect of the saccadic system. Patients were retested 1 month later, and stability of gain was high even in formerly drug-naive subjects who had been treated for 1 month with neuroleptic drugs. Altogether these results confirm the conclusions of most previous studies, extend them to drug-naive schizophrenic patients, and favor the hypothesis that SPEM impairment is a trait marker in schizophrenia.