Nashner L M
Exp Brain Res. 1976 Aug 27;26(1):59-72. doi: 10.1007/BF00235249.
Doubt about the role of stretch reflexes in movement and posture control has remained in part because the questions of reflex "usefulness" and the postural "set" have not been adequately considered in the design of experimental paradigms. The intent of this study was to discover the stabilizing role of stretch reflexes acting upon the ankle musculature while human subjects performed stance tasks requiring several different postural "sets". Task specific differences of reflex function were investigated by experiments in which the role of stretch reflexes to stabilize sway doing stance could be altered to be useful, of no use, or inappropriate. Because the system has available a number of alternate inputs to posture (e.g., vestibular and visual), stretch reflex responses were in themselves not necessary to prevent a loss of balance. Nevertheless, 5 out of 12 subjects in this study used long-latency (120 msec) stretch reflexes to help reduce postural sway. Following an unexpected change in the usefulness of stretch reflexes, the 5 subjects progressively altered reflex gain during the succeeding 3-5 trials. Adaptive changes in gain were always in the sense to reduce sway, and therefore could be attenuating or facilitating the reflex response. Comparing subjects using the reflex with those not during so, stretch reflex control resulted in less swaying when the task conditions were unchanging. However, the 5 subjects using reflex controls oftentimes swayed more during the first 3-5 trials after a change, when inappropriate responses were elicited. Four patients with clinically diagnosed cerebellar deficits were studied briefly. Among the stance tasks, their performance was similar to normal in some and significantly poorer in others. Their most significant deficit appeared to be the inability to adapt long-latency reflex gain following changes in the stance task. The study concludes with a discussion of the role of stretch reflexes within a hierarchy of controls ranging from muscle stiffness up to centrally initiated responses.
对牵张反射在运动和姿势控制中作用的怀疑一直存在，部分原因是在实验范式设计中，反射“有用性”和姿势“设定”的问题未得到充分考虑。本研究的目的是在人类受试者执行需要几种不同姿势“设定”的站立任务时，发现作用于踝关节肌肉的牵张反射的稳定作用。通过实验研究反射功能的任务特异性差异，在这些实验中，牵张反射在站立时稳定摆动的作用可以被改变为有用、无用或不适当。由于该系统有许多替代的姿势输入（如前庭和视觉），牵张反射本身对于防止失去平衡并非必要。然而，本研究中12名受试者中有5名使用长潜伏期（120毫秒）牵张反射来帮助减少姿势摆动。在牵张反射的有用性意外改变后，这5名受试者在随后的3 - 5次试验中逐渐改变反射增益。增益的适应性变化总是朝着减少摆动的方向，因此可能是减弱或增强反射反应。将使用反射的受试者与不使用反射的受试者进行比较，当任务条件不变时，牵张反射控制导致的摆动较少。然而，这5名使用反射控制的受试者在改变后的前3 - 5次试验中，当引发不适当反应时，往往摆动得更多。对4名临床诊断为小脑功能缺陷的患者进行了简要研究。在站立任务中，他们在某些方面的表现与正常人相似，而在其他方面则明显较差。他们最显著的缺陷似乎是在站立任务改变后无法适应长潜伏期反射增益。研究最后讨论了牵张反射在从肌肉僵硬度到中枢发起反应的控制层次中的作用。
