Simmons R W, Richardson C
Motor Performance Laboratory, San Diego State University, CA.
Brain Res. 1988 Nov 8;473(1):134-40. doi: 10.1016/0006-8993(88)90324-1.
Two experiments investigated whether unexpected and differential loading of a rapid, unsighted arm movement resulted in the central nervous system (CNS) regulating limb stiffness by modifying the associated neuromuscular activity. In Experiment 1, subjects completed multiple, spring-loaded training trials until a prespecified criterion of learning was attained. On selected trials, the spring load was unexpectedly replaced by an inertial load. Results indicated that to maintain positional accuracy during this inertial load trial, limb stiffness was increased by coactivating the antagonist muscles, i.e. by changing the associated neuromuscular activity from a predominantly triphasic pattern to one of coactivation. In Experiment 2, the sequence of loading was reversed producing a change in the required limb stiffness from a relatively high to low level. This change was observed as a pattern of coactivation being replaced by a triphasic activity pattern. These results support the notion that limb stiffness is regulated primarily through modification of the neuromuscular activity pattern prior to movement termination. It was also demonstrated that the size of the unexpected load did not affect the basic activation pattern selected by the CNS. It is proposed that the signal which triggers the CNS to regulate limb stiffness is based on peripheral information generated as a result of agonist activity occurring during the first part of the movement.
两项实验探究了快速、盲视的手臂运动中意外的和不同的负荷是否会导致中枢神经系统（CNS）通过改变相关的神经肌肉活动来调节肢体僵硬度。在实验1中，受试者完成多次弹簧加载的训练试验，直到达到预先设定的学习标准。在选定的试验中，弹簧负荷意外地被惯性负荷取代。结果表明，为了在该惯性负荷试验中保持位置准确性，通过共同激活拮抗肌增加了肢体僵硬度，即通过将相关的神经肌肉活动从主要的三相模式改变为共同激活模式。在实验2中，负荷顺序颠倒，导致所需肢体僵硬度从相对较高水平变为较低水平。这种变化表现为共同激活模式被三相活动模式取代。这些结果支持了这样一种观点，即肢体僵硬度主要是在运动终止前通过改变神经肌肉活动模式来调节的。还证明了意外负荷的大小不影响中枢神经系统选择的基本激活模式。有人提出，触发中枢神经系统调节肢体僵硬度的信号是基于运动第一部分中由于主动肌活动而产生的外周信息。
