The influence of Coriolis cross-coupling stimulation on postural sway and eye movement

Coriolis cross-coupling stimulation evokes not only curious eye movements but also postural sway However, it has not been clear whether postural sways are subject to the same regularity found in eve movements. The purpose of this study was to compare postural sways with eye movements in Coriolis cross-coupling stimulation. Six normal subjects were asked to execute 30 degrees head tilting under vision and nonvision while standing on a force platform at the center of a turntable. The turntable was rotated in a clockwise direction at different velocities. The center of pressure was determined continuously. Eye movements were recorded simultaneously using an infrared CCD-video camera. Some subjects touched the handrail of the turntable at rotation velocities greater than 30 degrees/sec when their surroundings were blocked from view. In contrast, no subjects touched the handrail at any rotation velocity when they were able to see their surroundings at any rotation velocity. The center of pressure was markedly displaced by head tilting when the surroundings were blocked from view in the same may as torsional nystagmus was evoked, neither the center of pressure nor gaze were destabilized when the surroundings were visible. Postural sways and eve movements showed similar tendencies. These results can be explained theoretically by vector. analysis of the supposed internal framework in the brain representing the perceived outer world.