| Research Abstract |
Since the first study reported by Holzman (1973), the disturbance of smooth pursuit eye movement in schizophrenia has been confirmed by many reseachers. To investigate the role of the frontal eye field (FEF) on the eye movement disorders in schizophrenics, we conducted the following animal experiments. Two head fixed Japanese monkeys were trained for tracking a target spot that moved smoothly (pursuit task) or stepwise (saccade task) with or without sinusoidal rotation of the whole body in either the pitch or yaw plane. Cells that showed modulation in their activity during these tasks were recorded in the arcuate sulcus and its close vicinity particularly in the caudal part. The activity of the great majority of pursuit-related cells was modulated by whole body rotation when the monkeys suppressed the vestibulo-ocular reflex (VOR) by fixating the target that rotated with them, suggesting that they may carry a gaze related signal. Some of these cells responded to vestibular stimulation in complete darkness. We also recorded saccade-related cells, but they rarely responded to vestibular stimulation.
Chemical deactivation of the FEF by infusion of a GABA agonist, muscimol, into the pursuit-related areas resulted in a decrease of gain (eye/stimulus) of the smooth pursuit eye movement with an increase of the number of catch-up saccades. VOR suppression was also impaired particularly at higher stimulus frequencies. In the visually guided saccade task, gains of saccades decreased and latencies increased. These results suggest that the eye movement disturbances observed in schizophrenic patients could possibly be explained by dysfunction of the frontal lobe including the FEF.
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