The visual and frontal cortices.

Abstract

The saccadic system uses a muscular apparatus and motor programs that evolved long before the cerebral cortex assumed the dominant role in the generation of behavior that it occupies in the primate. The cortical role in eye movements therefore is to contribute aspects of sophisticated processing to the basic apparatus for rapid eye movements. Thus visual cortex is necessary for the integration of visual motion information into the saccadic system, because the superior colliculus in the primate cannot do adequate motion processing. Similarly, frontal cortex is necessary for performing saccades to remembered stimulus positions, whereas visually driven saccades can be performed by the colliculus alone. To generate saccade-related information, the cortex has activity that reflects all levels of processing, from the registration of the stimulus and the selection of a stimulus for a saccade, to the elaboration of the motor command for the saccade. Presumably the cortex also contains the decision mechanism, whereby a primate decides to make a saccade to a certain stimulus. How, and where that decision is made, or even if the decision occurs at a single place, is totally unknown.