A Dynamical Moedl of Context Dependencies for the Vestibulo-Ocular Reflex

The vestibulo-ocular reflex (VOR) stabilizes images on the retina during rapid head motions. The gain of the VOR, i.e. the ratio of eye to head rotation velocity, measured with the eyes focused at a distance is typically around -1. However, to stabilize images accurately, the vestibulo-ocular reflex response must be modulated by the context in which the response takes place. The context studied in this paper includes eye position, eye vergence and head translation. We first describe a kinematic model of the vestibulo-ocular reflex response given rotational and translational information of the head motion. We then show how the model can be modified to rely solely on sensory information available from the semicircular canals (head rotation), the otoliths (head translation), and neural correlates of eye position and vergence angle. We then suggest a dynamical model and compare it to the eye velocity responses measured in monkeys (Snyder and King, 1992). The VOR response is nearly identical to an ideal theoretical response taking into account sensory input delays. The model captures the dynamical modulation of the VOR for this context. It defines which neural signals should be combined and suggests one possible way to perform the required computations in time. It therefore provides a theoretical explanation for the sensitivity of neurons to multiple inputs (head rotation and translation, eye position, etc.) in the pathways of the VOR.