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 eye field (SEF) in eight hemispheres of five Cebus apella monkeys. Monkeys were immobilized during experiments with Telazol (tiletamine HCl and zolazepam HCl), a dissociative anesthetic agent that was demonstrated to have no significant effect on microstimulation-induced eye movement 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 microstimulation 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 long stimulus trains. The results strongly support the proposal that the SEF produces not only saccadic eye movements as previously reported but also slow (pursuit) eye movements.