SLOW AND SACCADIC EYE-MOVEMENTS EVOKED BY MICROSTIMULATION IN THE SUPPLEMENTARY EYE FIELD OF THE CEBUS MONKEY

1. Intracortical microstimulation was used to map the supplementary ey e field (SEF) in eight hemispheres of five Cebus apella monkeys. Monke ys were immobilized during experiments with Telazol (tiletamine HCl an d zolazepam HCl), a dissociative anesthetic agent that was demonstrate d to have no significant effect on microstimulation-induced eye moveme nt parameters compared with similar experiments in alert, behaviorally trained monkeys. The functional subregions were defined with the use of low-threshold current (less than or equal to 50 mu A). Electrically elicited eye movements were videotaped and quantified. Both slow and saccadic eye movements were reliably evoked at low threshold by micros timulation in each of eight hemispheres studied. The two types of eye movements were clearly distinguished by their significantly different duration and velocity (P < 0.0001) and their different responses to lo ng stimulus trains. The results strongly support the proposal that the SEF produces not only saccadic eye movements as previously reported b ut also slow (pursuit) eye movements.