The control of rapid limb movement in the cat. III. Agonist - antagonist coupling.
The control of rapid limb movement in the cat. III. Agonist - antagonist coupling.
复制标题
猫快速肢体运动的控制。
DOI：
10.1007/bf00235770
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发表时间：
1982
影响因子：
2
通讯作者：
Martin,JH
中科院分区：
文献类型：
--
作者：
Ghez,C;Martin,JH
与快速自主肢体运动相关的肌电图（EMG）活动表现出典型的“三爆发模式”。第一次爆发发生在激动肌（AG1），第二次发生在拮抗剂（ANT），第三次再次发生在激动肌（AG2）。本研究旨在确定ANT和AG2是否反映了肢体位移后的预编程命令或拉伸反应。为了回答这个问题，我们在执行跟踪任务的猫身上检查了激动剂和拮抗剂肌肉的肌电图活动。为了将中央编程的肌肉事件与其预期的机械后果分离开来，等长和非等长条件以可预测或不可预测的顺序呈现。采用力矩电机控制四肢运动轨迹并施加被动角位移。AG1在等长和非等长条件下都存在，而ANT和AG2则需要肢体位移，并且时间锁定在运动参数上。ANT在加速开始后15ms内发生。其大小与该参数成线性关系，与AG1成反比。对于给定的加速度，被动位移拉伸拮抗剂引起的反应具有相似的潜伏期和最大的幅度。AG2仅存在于欠阻尼运动中，伴有末端振荡，通常发生在位置达到峰值且速度再次过零时。它的大小是肢体减速和预期力的函数。数据表明，ANT和AG2都代表了对肌肉拉伸的反应，其振幅由下行命令调节。在脊柱水平运行的互惠机制可以解释拮抗剂反应作为预期力的功能的减少。在高预期力的激动剂中，后期拉伸反应的敏感性增加与张力下降命令的运动神经元促进是相容的。有人提出，拉伸诱发反应的作用是抑制肢体质量在肌肉和软组织弹性力作用下的快速位移所引起的末端振荡。
Electromyographic (EMG) activity associated with rapid voluntary limb movements exhibits a characteristic “three burst pattern”. The first burst is in the agonist muscle (AG1), the second is in the antagonist (ANT) and the third is again in the agonist (AG2). The present study was undertaken to determine whether ANT and AG2 reflect preprogrammed commands or responses to stretch consequent upon limb displacement. To answer this question EMG activity of agonist and antagonist muscles was examined in cats performing a tracking task. To dissociate centrally programmed muscular events from their intended mechanical consequences, isometric and anisometric conditions were presented in either a predictable or unpredictable sequence. A torque motor was used to control limb trajectory and to impose passive angular displacements.Whereas AG1 was present under both isometric and anisometric conditions, ANT and AG2 required limb displacement and were time locked to movement parameters. ANT occurred within 15 ms following the onset of acceleration. Its magnitude varied linearly with this parameter and inversely with AG1. Passive displacements stretching the antagonist elicited responses with similar latencies and greatest magnitude for a given acceleration. AG2 was only present in underdamped movements with terminal oscillations and typically occurred when the position reached its peak and the velocity recrossed zero. Its magnitude was a function of both limb deceleration and of intended force.The data indicate that both ANT and AG2 represent responses to muscles stretch whose amplitudes are modulated by descending commands. Reciprocal mechanisms operating at a spinal level could account for the reduction of the antagonist response as a function of intended force. The increased sensitivity of late stretch responses in the agonist with higher intended forces is compatible with motoneuron facilitation by tonic descending commands. It is proposed that the stretch evoked responses function to dampen terminal oscillations which ensue from rapid displacement of the mass of the limb against elastic forces of muscle and soft tissue.