Forget R, Lamarre Y
Ecole de réadaptation, Faculté de médecine, Université de Montréal, PQ, Canada.
Can J Physiol Pharmacol. 1995 Feb;73(2):285-94. doi: 10.1139/y95-039.
Postural adjustments to imposed (passive) and voluntary (active) unloading conditions of the forearm were studied in normal subjects and a deafferented patient. The latency of the postural behaviour (deactivation of the biceps supporting the weight) was linearly related to the displacement amplitude of the unloaded forearm, independent of the unloading conditions. The postural behaviour consisted of an anticipatory postural adjustment (APA) occurring prior to active unloading (in both normals and the patient) and conversely in an unloading reflex response following passive unloading (only in the normals). In both the deafferented and the normal subjects, the amplitudes of the displacement during active unloadings were much smaller (3x) than in the passive conditions and an APA was present in both the deafferented and the normal subjects. The APA could not be triggered by some types of active movement and was absent when the movement was not directly producing the unloading. The EMG latencies of the APA and of the contralateral muscles used to unload were tightly coupled. However, the latency would sometimes be decoupled, particularly when a temporal delay was introduced between the active movement and the unloading in normal subjects. In contrast to the normal subjects, who were able to adapt quickly to an unusual unloading condition (produced by voluntary knee flexion), the deafferented patient did not show an APA in this task. It was concluded that, although the APA is of central origin, it cannot be generated only on the basis of internal timing cues and must rely on afferent information for its generation during unfamiliar unloading conditions.
在正常受试者和一名去传入神经的患者中，研究了前臂在施加的（被动）和自主的（主动）卸载条件下的姿势调整。姿势行为（支撑重量的肱二头肌失活）的潜伏期与卸载前臂的位移幅度呈线性相关，与卸载条件无关。姿势行为包括主动卸载之前（正常人和患者均如此）出现的预期姿势调整（APA），相反，在被动卸载后的卸载反射反应中（仅在正常人中）也存在。在去传入神经的受试者和正常受试者中，主动卸载期间的位移幅度比被动条件下小得多（3倍），并且去传入神经的受试者和正常受试者均存在APA。某些类型的主动运动无法触发APA，当运动未直接产生卸载时，APA不存在。APA和用于卸载的对侧肌肉的肌电图潜伏期紧密耦合。然而，潜伏期有时会解耦，特别是当在正常受试者的主动运动和卸载之间引入时间延迟时。与能够快速适应异常卸载条件（由自主屈膝产生）的正常受试者不同，去传入神经的患者在该任务中未表现出APA。得出的结论是，尽管APA起源于中枢，但它不能仅基于内部时间线索产生，在不熟悉的卸载条件下其产生必须依赖传入信息。
