Study of action control using vector analysis of surrounding space

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Tilting of the head during rotation produces strange sensation, body sways and nystagmus when examined in the dark. However, these phenomena are not evoked in the dark. The difference may be simply explained supposing a vector of surrounding outer world in the brain. The present study was done to answer following questions : a) whether the difference between vision and non-vision conditions hold good at fast rotations; b) how far adaptation proceeds by repetitive stimuli; c) whether training effects are different between vision and non-vision conditions; d) whether adaptation against Coriolis stimulation fits the hypothesis of vector analysis. In 1999, we modified a computer-controlled rotating chair into a rotating platform. In 2000, we investigated success rates of stance during Coriolis stimulation at different speeds. Although success rates differed between vision and non-vision conditions at 50 deg/s, they did not differ at 70 deg/s and faster speeds. In 2001, we studied training effects with (N=10) and without vision (N=10) on rotating velocities for successful stance and nature of acquired standing abilities. After daily 20-min-long training with Coriolis stimulation, more than half of the subjects could stand at 200 deg/s irrespective of visual condition. Reversed rotation after training degraded stance similarly as before training. In contrast, stance against lateral tilting was almost equal to forward tilting after training. We summarize the present study as follows, a) stance became quickly adapted itself to Coriolis stimulation; b) maximum rotation speed far exceeds 200 deg/s; c) vision does not influence training effect; d) adaptation of spatial orientation to Coriolis stimulation may be explained by a transfer of reference frame from stationary space to rotating space.