Paloski W H, Black F O, Reschke M F, Calkins D S, Shupert C
KRUG Life Sciences, Houston, Texas.
Am J Otol. 1993 Jan;14(1):9-17.
Orbital spaceflight exposes astronauts to an environment in which gravity is reduced to negligible magnitudes of 10(-3) to 10(-6) G. Upon insertion into earth orbit, the abrupt loss of the constant linear acceleration provided by gravity removes the otolith stimulus for vestibular sensation of vertical orientation constantly present on Earth. Since the central nervous system (CNS) assesses spatial orientation by simultaneously interpreting sensory inputs from the vestibular, visual, and proprioceptive systems, loss of the otolith-mediated vertical reference input results in an incorrect estimation of spatial orientation, which, in turn, causes a degradation in movement control. Over time, however, the CNS adapts to the loss of gravitational signals. Upon return to Earth, the vertical reference provided by gravitational stimulation of the otolith organ reappears. As a result, a period of CNS readaptation must occur upon return to terrestrial environment. Among the physiological changes observed during the postflight CNS readaptation period is a disruption of postural equilibrium control. Using a dynamic posturography system (modified NeuroCom EquiTest), 16 astronauts were tested at 60, 30, and 10 days preflight and retested at 1 to 5 hours, and 8 days postflight. All astronauts tested demonstrated decreased postural stability immediately upon return to Earth. The most dramatic increases in postural sway occurred during those sensory conditions in which both the visual and proprioceptive feedback information used for postural control were altered by the dynamic posturography system, requiring reliance primarily upon vestibular function for control of upright stance. Less marked but statistically significant increases in sway were observed under those conditions in which visual and foot support surface inputs alone were altered.(ABSTRACT TRUNCATED AT 250 WORDS)
轨道航天使宇航员暴露于一种重力降至可忽略不计的环境，重力大小为10的负3次方至10的负6次方G。进入地球轨道后，重力提供的恒定线性加速度突然消失，消除了地球上持续存在的用于垂直方向前庭感觉的耳石刺激。由于中枢神经系统（CNS）通过同时解释来自前庭、视觉和本体感觉系统的感觉输入来评估空间定向，耳石介导的垂直参考输入的丧失导致对空间定向的错误估计，进而导致运动控制能力下降。然而，随着时间的推移，中枢神经系统会适应重力信号的丧失。返回地球后，耳石器官受重力刺激提供的垂直参考重新出现。因此，返回地面环境后必须经历一段中枢神经系统重新适应的时期。在飞行后中枢神经系统重新适应期观察到的生理变化中，有姿势平衡控制的紊乱。使用动态姿势描记系统（改良的NeuroCom EquiTest），对16名宇航员在飞行前60天、30天和10天进行测试，并在飞行后1至5小时和8天进行重新测试。所有接受测试的宇航员返回地球后立即表现出姿势稳定性下降。姿势摆动最显著的增加发生在那些感觉条件下，即用于姿势控制的视觉和本体感觉反馈信息都被动态姿势描记系统改变，需要主要依靠前庭功能来控制直立姿势。在仅视觉和足部支撑表面输入被改变的条件下，观察到摆动有不太明显但具有统计学意义的增加。（摘要截短于250字）
