Long-term adaptive changes in primate vestibuloocular reflex. III. Electrophysiological observations in flocculus of normal monkeys.

Abstract

The discharge characteristics of 1239 single units recorded in the flocculus of alert monkeys (Macaca mulatta) were studied in relation to visual, vestibular and oculomotor events in a variety of paradigms. Animals were trained to fixate small target lights and required to perform various tracking tasks designed to facilitate the quantitative analysis of associated unit discharges. Units were subdivided into 3 groups: granular layer input elements, interneurons, and Purkinje output cells (P-cell). Apparently the gaze velocity P-cells have an important role in improving ocular pursuit. A model is proposed which incorporates the gaze velocity P-cells into the pursuit system and the vestibuloocular reflex; the eye velocity component of P-cell discharge is an efferent copy signal configured to provide positive feedback support for ocular pursuit; and the head velocity component is part of an inhibitory side loop of the vestibuloocular pathway operating to offset the loss of eye velocity positive feedback support during combined eye-head tracking.