Collins J J, De Luca C J, Pavlik A E, Roy S H, Emley M S
Neuromuscular Research Center, Boston University, MA 02215, USA.
Exp Brain Res. 1995;107(1):145-50. doi: 10.1007/BF00228026.
Stabilogram-diffusion analysis was used to examine how prolonged periods in microgravity affect the open-loop and closed-loop postural control mechanisms. It was hypothesized that following spaceflight: (1) the effective stochastic activity of the open-loop postural control schemes in astronauts is increased; (2) the effective stochastic activity and uncorrelated behavior, respectively, of the closed-loop postural control mechanisms in astronauts are increased; and (3) astronauts utilized open-loop postural controls schemes for shorter time intervals and smaller displacements. Four crew members and two alternates from the 14-day Spacelab Life Sciences 2 Mission were included in the study. Each subject was tested under eyes-open, quiet-standing conditions on multiple preflight and postflight days. The subjects' center-of-pressure trajectories were measured with a force platform and analyzed according to stabilogram-diffusion analysis. It was found that the effective stochastic activity of the open-loop postural control schemes in three of the four crew members was increased following spaceflight. This result is interpreted as an indication that there may be in-flight adaptations to higher-level descending postural control pathways, e.g., a postflight increase in the tonic activation of postural muscles. This change may also be the consequence of a compensatory (e.g., "stiffening") postural control strategy that is adopted by astronauts to account for general feeling of postflight unsteadiness. The crew members, as a group, did not exhibit any consistent preflight/postflight differences in the steady-state behavior of their closed-loop postural control mechanisms or in the functional interaction of their open-loop and closed-loop postural control mechanisms. These results are interpreted as indications that although there may be in-flight adaptations to the vestibular system and/or proprioceptive system, input from the visual system can compensate for such changes during undisturbed stance.
采用稳定图扩散分析来研究长时间处于微重力环境如何影响开环和闭环姿势控制机制。研究假设如下：在太空飞行后，（1）宇航员开环姿势控制方案的有效随机活动增加；（2）宇航员闭环姿势控制机制的有效随机活动和不相关行为分别增加；（3）宇航员使用开环姿势控制方案的时间间隔更短，位移更小。该研究纳入了执行14天太空实验室生命科学2任务的4名机组人员和2名候补人员。在多个飞行前和飞行后的日子里，让每个受试者在睁眼、安静站立的条件下进行测试。使用测力平台测量受试者的压力中心轨迹，并根据稳定图扩散分析进行分析。研究发现，4名机组人员中有3名在太空飞行后开环姿势控制方案的有效随机活动增加。这一结果被解释为表明飞行过程中可能对更高层次的下行姿势控制通路产生了适应性变化，例如飞行后姿势肌肉的紧张性激活增加。这种变化也可能是宇航员为应对飞行后普遍的不稳定感而采取的一种补偿性（如“僵硬”）姿势控制策略的结果。作为一个整体，机组人员在闭环姿势控制机制的稳态行为或开环与闭环姿势控制机制的功能相互作用方面，飞行前/飞行后没有表现出任何一致的差异。这些结果被解释为表明，尽管飞行过程中可能对前庭系统和/或本体感觉系统产生了适应性变化，但在安静站立时，视觉系统的输入可以补偿此类变化。
