Rapid adaptation of the vestibulo-ocular reflex and induced self-motion perception

Abstract

Directional asymmetries of vestibular induced self-motion perception and the vestibulo-ocular reflex (VOR) were observed in darkness following adaptation to unidirectional movement of a large textured visual field. Following short-term adaptation (1 min) to visual motion with the body stationary, observers reported that their sensitivity to body rotation in darkness was reduced in the same direction as the previous adapting stimulus and was enhanced in the opposite direction. The duration of this aftereffect was at least six times longer than those of aftereffects of circular vection when the observer remained stationary in darkness. The opposite distortion of self-motion perception was observed after long-term visual adaptation (15 min) in which sensitivity to body rotation in darkness was reduced in a direction opposite to the adapting drum rotation. Changes in self-motion perception resulted from interactions between visually induced illusions of self-motion (vection) and habituation of vestibular induced self-motion perception. The short- and long-term aftereffects were both accompanied by reductions of slow-phase gain of the VOR when the body rotated in the same direction in which self-motion perception was reduced. If the observer was stationary in darkness, there was also a motion-induced afternystagmus. Following short-term adaptation, afternystagmus was too brief to interact with the modified VOR; following long-term adaptation, however, a sustained inverted afternystagmus could have summed linearly with the vestibular responses and caused an apparent modification of the VOR. A pure visual stimulus is believed to produce rapid modification of the VOR so that it can anticipate head movements and maintain stability of the retinal image while the observer tracks a moving visual field. © 1986 Psychonomic Society, Inc.