Basic parameters of saccadic eye movements – differences between unmedicated schizophrenia and affective disorder patients

Background Smooth pursuit eye movement (SPEM) dysfunctions are considered a biological marker for schizophrenia and have been studied widely. In contrast, saccadic eye movements have received less attention, although disturbances have been described previously. Basic neurophysiologic parameters of saccades in schizophrenics, especially in unmedicated patients, have not been studied extensively. Methods Saccadic eye movements of 38 unmedicated schizophrenic patients, 32 patients with major depression and 42 non-psychiatric controls were examined using high-resolution infrared oculography. Two large-amplitude saccadic tasks were presented. The groups were compared on peak velocity, reaction time and accuracy. Results Peak velocity was significantly increased in schizophrenic patients. Depressive patients had a significantly longer reaction time. Both patient groups needed more corrective saccades to reach the target than controls. Conclusions Peak velocity distinguishes unmedicated schizophrenic patients from depressive patients and normal controls. This could be explained by deficits of the prefrontal cortex in the inhibitory control of saccades. Our findings suggest that schizophrenia affects not only SPEM but also saccadic eye movements.