Abstract
Some previous studies have confirmed that vection is facilitated by adding random oscillation to a visual stimulus and that the magnitude of facilitation varies according to the frequency of the oscillation. Fernandez and Goldberg (1971, 1976) have found that the dynamics of the vestibular system of monkeys varies according to the frequency of the acceleration stimulus. We hypothesize that facilitation is related to the dynamics of the vestibular system. Hence, in the present study, we examined the effect of random or periodic oscillation added to a visual stimulus in relation to the dynamics of the vestibular system. A visual stimulus that simulated an ordinary mountain road was rendered in real time. The visual stimulus simulated forward self-motion by adding random or periodic oscillation with a head mounted display for a period of 90 s. The stimulus conditions comprised of combinations of ten types of frequency and four types of oscillation direction (horizontal & vertical, pitch, yaw, and roll). Forty young adults participated in the study were naïve as to the purpose of the experiment., and had normal or corrected-to-normal visual acuity. During the trials, at the time of experiencing vection, they continuously indicated the change in the strength of vection using a subjective response box to evaluate the perception of severity on a 5-point scale. When each types of low frequency-oscillation was added to the visual stimulus, the strength was greater and the duration was longer than those observed when no oscillation was added to the visual stimulus regardless of whether the oscillation was random or periodic.