空間識・シリーズ教育講座 １３．トレーニングと空間識

Abstract

To confirm that stance is adaptive to high-speed Coriolis stimulation, we stimulated 20 healthy volunteers on 9 consecutive days, with or without vision. They stood on a rotating platform and at 1-min intervals tilted the head forward and returned it upright. We determined the initial maximum rotation speed for each individual and performed 20-min stimulation at that speed on day 1. Beginning on day 2, rotation speed was increased by 20°/s up to a maximum of 200°/s. Mean maximum speeds on the first and ninth days were 84°/s and 193°/s, respectively, in the vision group and 57°/s and 186°/s, respectively, in the non-vision group. Maximum speeds in the vision group were significantly greater than those in the non-vision group, but vision did not influence the increase to maximum speed during the 9-days training period. After the training period, both groups showed similar response to side-to-side head tiliting as they showed to forward tilting. However, on day 11, the groups did not respond similarly to a reversal in the rotation direction. Maximum rotation speed on day 11 was close to that of day 1. The results from the present study suggest that stance stability was attained by temporary adaptation of spatial orientation to the rotating environment. Vector analysis indicates that once a rotating space, instead of a stationary space, is represented as a spatial framework, inertial inputs at head tilting are canceled by fusion with the velocity vector of the new reference frame.