Development of moving visual stimulation method for linear acceleration experiment using a virtual reality graphic display

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The otolith organ in the inner ear perceives both the gravity and linear acceleration, so it is susceptible to the change of body position. Information of the body position gets also according to visual system together with the vestibular one. We developed an optokinetic stimulation pattern which was drawn up by a virtual reality computer graphics (CG), and intended to combine visual and vestibular stimulation using a linear acceleration equipment (sled) installed at Nagoya University. (1) From 1995 through 1996, main research subject was to accomplish the virtual reality stimulation patterns, which acted in cooperation with movement of the sled. (2) During preparing CG by a soft-ware maker, the other subject was proceeded, so that it was to examine an effect of linear acceleration on the postural readjustment response. When the sled was driven with a sinusoidal motion of fore and back to subject body swayd in proportion to a magnitude of driven acceleration. (3) It was clarified that … More two types of the postural control were distinguished between 0.04G and 0.06G.Namely, in 0.02G to 0.04G the postural readjustment was controlled by an ankle strategy, and in 0.06G to 0.08G a hip strategy was dominated. Head movement was fixed and stabilized at the higher G above 0.06G.(4) These phenomena were also proved by the muscle activities of the neck and under extremity muscles. As a possible explanation, the vestibulo-collic as well as the vestibulo-spinal reflexes were discussed. (5) The next experiment performed in 1996 to 1997 was to study effects of optokinetic stimulation produced by the CG on the standing posture. The optokinetic stimulation caused a self-motion perception (vection) to the subject, and simultaneously provoked a body sway corresponded with the visual stimulation. (6) It was defined that the vection produced firstly head movement and then the body sway which was triggered by the head movement. (7) Unfortunately, during the term of this project we could not conduct the sled experiment by using a newly developed virtual reality optokinetic stimulation experiment owing to severe restriction of utilization of the sled of Nagoya University. Less