CEREBRAL CORTICAL MECHANISMS FOR EYE MOVEMENTS AND VISUAL ATTENTION

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The functional nature of the projection from the frontal eye field to the brain stem has been studied in the rhesus monkey. Like the frontotectal projection, the frontopontine projection contains cells which discharge in association with eye movements or visual fixation, but not cells which have exclusive peripheral visual responses. The nature of the visual stimuli evoking smooth pursuit were was studied using open-loop visual methods. Superimposition of open- loop position and velocity errors during pursuit maintenance resulted in the generation of eye velocities that indicated that stimulus position as well as stimulus velocity is an important stimulus for the maintenance of smooth pursuit. The time course and dynamics of uniocular saccadic adaptation were studied in monkeys who were made to adapt to a weakened eye. At first the weakened eye had a hysteresis in orbital position, and an orbital-position-dependent saccadic inaccuracy. Both the hysteresis and the orbital position dependent effects were compensated for in a point by point manner with experience. The results suggest that the oculomotor system has a complicated and sensitive corrective mechanisms for the non-linearity of orbital mechanics. Any physical derangement causes maladjustment of this compensation, which can be adapted in time.