Smooth pursuit performance in families with multiple occurrence of schizophrenia and nonpsychotic families

Background: Eye tracking dysfunction (ETD) has been put forward as a trait marker for biological susceptibility to schizophrenia with the hope of identifying a link to specific cerebral lesions. Methods: Eye movements were recorded using infrared oculography in 8 families (67 members) showing multiple occurrence of schizophrenia and in 9 nonpsychotic families (80 members). Triangle wave stimuli at 15°/s and 30°/s were used and gains (eye velocity/target velocity), rates and amplitudes of different saccade categories (catch-up, back-up, anticipatory saccades, and square-wave-jerks) were determined. Results: In the relatives, the same deficit in maintenance of smooth pursuit performance was found as was seen in the schizophrenic patients. This deficit, which was not observed in the nonpsychotic families, consisted of lower gains for leftward as compared to rightward pursuit. This was emphasized most clearly at 30°/s and was associated with an excess of catch-up saccades in the schizophrenic patients, whereas in the relatives a tendency to exhibit more and larger anticipatory saccades was observed. Conclusions: The results confirm the hypothesis that eye-tracking dysfunction is a phenotypic marker for genetic liability to schizophrenia. Neurophysiologically, a cerebral dysfunction which includes one or more of the oculomotor centers can be assumed in subjects who carry a genetic susceptibility to schizophrenia