The object of this research is to determine how and where slow and rapid eye movements are generated. Specifically, we are working to localize the neural mechanism responsible for generating rapid eye movements in all directions. We postulate that this mechanism is located in the reticular formation of the rostral pons. We also are studying an integrator whose state or output is associated with the vestibular nuclei and the prepositus nucleus, to determine how it is utilized for the production of slow eye movements. This integrator appears to be a focus for the interaction between the visual and vestibular systems. Experiments are done in alert monkeys. The animals receive visual and vestibular stimulation before and after lesions. Vestibular stimuli consist of constant velocity and sinusoidal rotation about vertical and horizontal axes. These stimuli induce optokinetic nystagmus (OKN), optokinetic after-nystagmus (OKAN), and per and post rotatory nystagmus. Pursuit eye movements are elicited by sinusoidal movement of tracking targets. Extracellular unit activity and eye movements will be analyzed in the time and frequency domains and compared to predictions made from control systems models of the oculomotor system. Eye movements and unit activity before and after lesions will also be studied. This research should help elucidate the underlying organization of the oculomotor system for rapid eye movements in all planes. It should also lead to better understanding of the neurons in the brainstem that perform integration necessary to produce slow eye movements.