Investigation of the human visual system by phychophysical and fMRI experiments

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This research was aimed to investigate the human visual system by using psychophysical and fMRI experiments. In the psychophysical experiments, we used apparent self-motion, vection, elicited by viewing full-field motion presented by an evasive type virtual reality system (CAVE).1. Eye movements of the observers were recorded to examine the contribution of optokinetic nystagmus on the feeling of vection. Results indicated that the beating field during vection was found to displace to the perceived heading direction in proportion to the strength of vection. This displacement preceded the difference in the subjective estimation of the strength of vection between viewing conditions. Thus the strength of vection was estimated by measuring the beating field of optokinetic nystagmus even before the actual observation of the subjective estimation of vection.2. Each repertoire of the human senses has its specialty. While spatial superiority of vision over audition causes ventriloquism illusion, temporal superiority of audition over vision does cross-modal interactions that humans make a mistake in perceiving temporal characteristics of visual events with overlapped tones. We showed a phenomenon opposite to these biases; visual input modifies the perception of temporal characteristics of tones. In the experiment observers made a biased judgment of the temporal-order of two tones presented successively when they felt apparent self-motion (vection) by viewing full-field motion of a visual display presented by a virtual reality system. This result indicated that apparent self-motion plays an influential role in temporal perception.