Society for Neuroscience Abstract 1995

A MODEL FOR HOW THE CEREBELLUM ANTICIPATES SENSORY INPUTS AND MODULATES THE VESTIBULO-OCULAR REFLEX (VOR).

Olivier J.M.D. Coenen and T.J. Sejnowski.

The gain of the VOR in monkeys is modulated by many inputs including eye position, target distance and otolith signals. We have developed a kinematic equation for the VOR that describes how the signals from the vestibular canals and otoliths can be combined with eye position and vergence angle signals to give the ideal VOR response for any head rotation and translation in three dimensions. By simulating head rotations for different locations of the axis of rotation, and by including delayed otolith and canal inputs, we obtain results which quantitatively match the VOR dynamics observed in monkeys (Snyder & King; J.Neurophys. 67:4,1992).

We have also developed a dynamic model for how the nonlinear modulation of the VOR could be learned. Snyder & King (Vision Res.32:3,1992) have shown that the gain of the VOR changes in anticipation of vergence movements and have suggested that a central command signal could drive the vergence system and the VOR response via the cerebellum. Our adaptive cerebellar model describes how such a central command signal can 1) become associated with the modulation of the VOR and 2) produce anticipatory modulation of the VOR to compensate for retinal slips which may occur hundreds of milliseconds later. The model is a dynamical neural network represented by a set of differential equations. Computer simulations of the model show how the cerebellum may construct predictive representations of the retinal slip signals which can modulate the gain of the VOR in anticipation of new behavioral conditions.