The Anatomy and Physiology of Primate Neurons that Control Rapid Eye Movements

Primates are frontal eyed animals possessing a sophisticated retina endowed with a highly differentiated foveal region with which the visual scene can be examined in detail. Vision is very important to these animals and is probably the predominant sensory modality with which they orient themselves and interact with the world. The relationship between the visual system and the motor system that moves the eyes (oculomotor) is intimate. Motion of the visual scene across the retina, particularly the fovea, can degrade visual acuity. Hence there is a necessity for accurate oculomotor control. Not surprisingly, a considerable portion of the brain� including the superior colliculus (sq, the frontal eye field (FEF), the thalamus, and the cerebellum as well as several brainstem nuclei, is entrusted with the control of eye movements (Hepp et al 1989). The most ubiquitous movements of the eyes are the rapid ones (also called saccadic) that reorient the eyes quickly toward interesting features of the surrounding world. During a saccade, two or more of six extraocular muscles