Single Unit Recordings in the Vestibular Nuclei of the Alert Monkey Related to the Vertical Vestibulo-Ocular Reflex (VVOR)

Abstract

Study of the vestibular system’s role in oculomotor function has concentrated on motion in horizontal planes parallel to earth to simplify experimental paradigms. Thus, the logic is that passive and active head rotations involving only events in the horizontal semicircular canals (SCC), exclusive of those for example in the vertical SCC and the otolith organs, need be correlated with the actions of only two of six extraocular muscles for one eye, i.e. the medial and lateral recti. As productive as this research has been in defining vestibulo-ocular relations, it is evident that head and eye movements in the horizontal plane are but a fraction of the overall eye and head motion. Involved here is the general problem of how head movement information, detected in the three dimensions of the SCC, is projected onto the oculomotor system, having only two dimensions of movement--if torsions are neglected. Analysis of premotor neurons has already revealed complex iso-frequency curves in two dimensional space (Henn, Hepp, 1981). To be more specific, then, it is necessary to determine how the vestibular system interfaces with such premotor neurons, and subsequently with oculo-motoneurons.