Abstract
Ohmi & Howard (1986) reported that the magnitude of OKN induced by temporonasal motion input is stronger than that induced by nasotemporal motion. If OKN and vection had some common mechanisms, the magnitude of vection should also show the same tendency. We examined this issue by measuring vection for hemifield / monocular motion stimulations. Experiment 1: We presented temporonasal and nasotemporal (horizontal) motion stimuli that subtended only within a hemifield to the subjects who observed them monocularly. The magnitude of vection was measured by using a magnitude estimation method. The stimuli were sinusoidal vertical gratings (contrast = 10%, SF = 0.07 c/degree). The Stimulus velocity was 36 degree/sec. The stimulus was not projected to the central visual field. The duration was 20 sec. Subjects were 8 naive volunteers. Each eye had 10 trials. Results: Temporonasal motion induced stronger vections than nasotemporal motion. In addition, contralateral input induced stronger vections than ipsilateral input. Experiment 2: A similar experiment was conducted with downward (vertical) motion stimuli. Subjects were 7 naive volunteers. Results: There was no significant difference in the vecttion magnitude between ipsilateral and contralateral stimulations. Discussion: The magnitude of vection and OKN correlated each other well. The effectiveness of contralateral information to vection suggests possibilities that certain subcortical mechanisms are shared between OKN and vection. The results from Experiment 2 suggest that the mechanism subserving vertical and horizontal vection may be at least partially different.