Effects of a visual-vestibular stimulus on the vestibulo-ocular reflex

Exposure before flight to an environment that provides altered visual-vestibular relationships similar to those seen in weightlessness might facilitate adaptation to spaceflight. Fifteen normal subjects were exposed for 0, 5, and 20 min to an abnormal visual-vestibular environment in which the vestibular sensation of lateral tilt was associated with the visual impression of lateral translation. Lateral eye movement elicited by similar tilt in darkness was measured before and at intervals after the exposure. Of the 15 subjects, 12 showed increased VOR amplitude following the exposure, but this increase appeared unrelated to the duration of exposure to the visual stimulus and may be an effect of the VOR measurement procedure. Most subjects showed little shift in the phase relationship between tilt and eye motion. Three subjects showed changes in VOR and five reported changes in perception of motion which appear clearly related to the visual-vestibular exposure.