Properties of Eye and Head Movements Evoked by Electrical Stimulation of the Monkey Superior Colliculus

On monkeys and cats, microstimulation of the superior colliculus evokes gaze movements containing both eye and head movement components. The superficial layers of the superior colliculus in these species contain a simple point-to-point representation of the retina. This retinotopic map is parallel with a movement activity map in the intermediate layers produced by neurons that are stimulated before and during saccades of specific amplitude and direction. Early reports of electrical stimulation of the monkey's superior colliculus with the head restrained focused on the correspondence of sensory and motor maps, finding that the trajectories of saccadic eye movements evoked by electrical stimulation, depended mainly upon the location of the stimulation site, with the eyes' orbital position having only a very slight effect upon the amplitude and direction of the evoked eye movement.