HYPOMETRIC PRIMARY SACCADES OF SCHIZOPHRENICS IN A DELAYED-RESPONSE TASK

In this study, the execution of delayed saccades in 15 DSM-III-R-schiz ophrenic patients and 15 normal subjects was investigated. While looki ng at a central fixation cross, a peripheral target was randomly prese nted at 10 degrees eccentricity. Subjects were instructed to saccade t o the target when the fixation cross was switched off after 500 ms. Tw o experiments were conducted: (a) a delayed-saccade task and, (b) a me mory-guided saccade task, that is, the peripheral target was switched off together with the fixation cross. In the delayed-saccade-task, amp litudes of regular saccades did not differ between schizophrenic patie nts and normals. In the memory-guided saccade task: schizophrenic subj ects showed marked hypometric saccades. Incorrect delayed saccades (wh ile the fixation cross was on) were also hypometric in schizophrenics, but not in normal controls. The final eye position, i.e., the positio n reached after the execution of correction saccades, however, did not differ between patients and controls. This means that schizophrenics show a deficit in the programming of primary saccades, if the fixation point and the peripheral target are (a) both visually presented or (b ) both memorized. The results support the hypothesis that these saccad es are the result of an averaging effect between the fixation point an d the peripheral target. It is further hypothesized that these deficit s might be explained by a lack of prefrontal inhibition of ocular fixa tion areas.