K Watanuki1, M Takahashi, T Ikeda. 1. Department of Otolaryngology, Yamaguchi University School of Medicine, Ube Japan. watanuki@po.cc.yamaguchi-u.ac.jp
Abstract
BACKGROUND: Motion sickness evokes not only discomfort but also marked equilibrium ataxia. However, its mechanism of ataxia remains unclear. HYPOTHESIS: We supposed that stance, gaze, and sensation may be uniformly controlled by the perception of the surrounding space. METHODS: Using Coriolis stimulation, we examined eight normal subjects and two patients with bilateral labyrinthine loss. They were asked to stand on a platform; then while being rotated clockwise 60 degrees x s(-1), they tilted their head 30 degrees. Displacement of the center of pressure and ocular movements were recorded using a force platform set on the device and an infrared CCD-video camera fixed to goggles, respectively. RESULTS: In normal subjects with eyes covered, tilting of the head resulted in shifts of the center of pressure and torsional or vertical nystagmus. When they could see the surroundings, they showed stable posture and optokinetic nystagmus regardless of head tilting status. In contrast, the two patients were not affected by head tilting when their eyes were covered, although they showed remarkable body swaying even while they were static. CONCLUSIONS: From the present study, it seems probable that posture, gaze, and sensation are absolutely controlled by the perception of surrounding space, which may be theoretically represented as a vector in the head.
BACKGROUND: Motion sickness evokes not only discomfort but also marked equilibrium ataxia. However, its mechanism of ataxia remains unclear. HYPOTHESIS: We supposed that stance, gaze, and sensation may be uniformly controlled by the perception of the surrounding space. METHODS: Using Coriolis stimulation, we examined eight normal subjects and two patients with bilateral labyrinthine loss. They were asked to stand on a platform; then while being rotated clockwise 60 degrees x s(-1), they tilted their head 30 degrees. Displacement of the center of pressure and ocular movements were recorded using a force platform set on the device and an infrared CCD-video camera fixed to goggles, respectively. RESULTS: In normal subjects with eyes covered, tilting of the head resulted in shifts of the center of pressure and torsional or vertical nystagmus. When they could see the surroundings, they showed stable posture and optokinetic nystagmus regardless of head tilting status. In contrast, the two patients were not affected by head tilting when their eyes were covered, although they showed remarkable body swaying even while they were static. CONCLUSIONS: From the present study, it seems probable that posture, gaze, and sensation are absolutely controlled by the perception of surrounding space, which may be theoretically represented as a vector in the head.