Stimulating the vestibular system for a certain period of time while changing the visual input using a reverse prism or lens is known to change the gain and phase of the vestibulo-ocular reflex (VOR); this phenomenon is known as VOR adaptation. The method for examining VOR adaptation involves addition of rotational stimuli and visual stimuli simultaneously in specific time units. Generally, black and white stripes are projected onto a circular screen when adding visual stimuli. When looking at the indicator moving on the circular screen, the subject perceives a circular vection (CV), as though it was turning in the opposite direction to the rotational direction of the visual stimulus. Conversely, the subject perceives a linear vection (LV) for a visual stimulus moving in a straight line, as though it was moving in the opposite direction to the linear of the visual stimulus. These results suggest that even if the indicator patterns are the same in the brain, rotational and linear movements may be processed as stimuli of different modalities. In this study, we added continuous rotational stimuli while projecting visual stimuli onto a flat screen, instead of the circular screen that is normally used for this test, to ascertain the effect of differences in the modality of movement of visual stimuli on VOR adaptation. We used two types of visual stimuli as the visual stimuli, namely, -1 stimulus, which is a visual stimulus in the same direction as the rotary chair, and the X2 stimulus, which is a stimulus in the opposite direction. There were no significant changes in gain for either pattern. Visual stimuli on a flat screen are perceived as linear stimuli, therefore, rotational stimuli are processed as inappropriate sensory information for VOR; thus, there is, no change in gain.
