The objective of the proposed research is to study brainstem and cerebellar nuclei which are part of or modulate pathways to oculomotoneurons. Threee major projects will be undertaken. First, the behavior of neurons in the brainstem of alert monkey and cat will be recorded while the animal is executing saccadic eye movements. Eye position will be accurately measured by an elctromagnetic technique and the animal will be rewarded for tracking a moving light spot. Correlations between the various parameters describing the saccadic trajectory and parameters describing unit discharge should reveal the role of different brainstem neurons in the production of a saccade. Second, units will be recorded in the vestibular nuclei of a monkey trained to track a moving target while simultaneously undergoing vertical head oscillations about a horizontal axis. By using various combinations of target and head rotations, it will be possible to determine the discharge characteristics of units with combined eye and head movement sensitivity so that the participation of these units in the vertical vestibuloocular relex (VOR) can be ascertained. Third, unit recordings will be obtained from the cerebellar flocculus of monkeys subjected to combined target and vestibular stimuli to test the role of the flocculus in short term modification of the vertical VOR. Visual pathways to the flocculus will be traced by electrophysiological and anatomical techniques.