Vision during angular oscillation: the dynamic interaction of visual and vestibular mechanisms.

A review is presented of the dynamic behaviour of two oculomotor control systems--the vestibulo-ocular and pursuit reflexes--responsible for the spatial and temporal stabilization of the image of an observed object on the fovea of the retina, and mathematical models adduced in which the contribution of physiological components of the systems can be identified. With angular oscillation of the head below 1-2 Hz, retinal information is used to maintain unity gain of the head/eye system, but at higher frequencies stabilization is determined primarily by vestibular inputs. When the observed target moves with the head, as in a head-mounted display, the suppression of inappropriate vestibulo-ocular responses is dependent upon the dynamic performance of the pursuit system. With such a display, impairment of visual acuity may be detected at frequencies of oscillation as low as 0.5 Hz.