Neural control of foveal pursuit versus saccadic eye movements in primates — Single-unit data and models

A framework for two oculomotor subsystems, an electromechanical pursuit system and the saccadic system, is proposed on the basis of neurophysiological findings in alert monkeys. This model is arranged into a sequence of spatiotemporal translation, motor program generation, and neural integration. For the purpose of foveal pursuit movements, an eye velocity signal must be internally generated and updated according to the current position error on the retina. This design probably involves a recently discovered class of pursuit neurons. Saccadic eye movements are probably controlled by burst neurons. Based on striking similarities between the neural activity of these recently analyzed burst neurons and Renshaw cells, a detailed quantitative model for the generation of preprogrammed saccades, the Renshaw model, is proposed. Open and controversial questions in the literature concerning various strategies being used by the primate oculomotor system are mentioned.