Pozzo T, Papaxanthis C, Stapley P, Berthoz A
Groupe Analyse du Mouvement (G.A.M), U.F.R. S.T.A.P.S., Campus Universitaire, Université de Bourgogne, B.P. 138, 21004, Dijon, France.
Brain Res Brain Res Rev. 1998 Nov;28(1-2):92-101. doi: 10.1016/s0165-0173(98)00030-7.
In order to demonstrate that gravity is not only a load acting locally and continuously on the body limbs, but is also used by higher levels of the nervous system as a dynamic orienting reference for the elaboration of the motor act, a review of several experiments conducted both in 1 g and 0 g are presented. During various locomotor tasks, the strategy that consists of stabilizing the head with respect to gravity illustrates one of the solutions used by the CNS to optimize the control of dynamic equilibrium. A question which remains to be solved when considering experimental results obtained in weightlessness concerns, however, the maintenance of motor schema that has evolved under normal gravity. Results have suggested that the concept of conservative processes, that would adapt postural control to weightlessness by using previously learned innate strategies, must be reconsidered during goal-oriented tasks. In fact, it is proposed that when conservative processes and existing solutions derived from a repertoire of terrestrial postural strategies do not provide efficient output, the CNS has to create novel strategies through a slow learning process. As with the study of postural control, three-dimensional arm reaching movements also illustrate the central representation of gravity. Indeed, gravity can be regarded as either initiating or braking arm movements and, consequently, may be represented in the motor command at the planning level. Finally, from a prospective point of view, there is a need to determine new experimental paradigms in order to study the specific motor control of man in space. It is suggested that the formulation of experimental paradigms should not consider man in space simply as a terrestrial biped.
为了证明重力不仅是局部且持续作用于身体四肢的负荷，而且还被神经系统的高级层面用作运动行为精细调节的动态定向参考，本文对在1g和0g环境下进行的多项实验进行了综述。在各种运动任务中，相对于重力稳定头部的策略体现了中枢神经系统（CNS）用于优化动态平衡控制的一种解决方案。然而，在考虑失重环境下获得的实验结果时，一个有待解决的问题是在正常重力环境下演化而来的运动模式的维持。结果表明，在面向目标的任务中，必须重新考虑保守过程的概念，即通过使用先前习得的先天策略使姿势控制适应失重环境。事实上，有人提出，当保守过程和源自一系列地面姿势策略的现有解决方案无法提供有效输出时，中枢神经系统必须通过缓慢的学习过程来创建新的策略。与姿势控制的研究一样，三维手臂伸展运动也体现了重力的中枢表征。的确，重力既可以被视为手臂运动的启动因素，也可以被视为制动因素，因此，在运动指令的规划层面可能会有所体现。最后，从前瞻性的角度来看，有必要确定新的实验范式，以便研究人类在太空中的特定运动控制。有人建议，实验范式的制定不应简单地将太空中的人类视为地面双足动物。
