Structured Variability of Muscle Activations Supports the Minimal Intervention Principle of Motor Control
Structured Variability of Muscle Activations Supports the Minimal Intervention Principle of Motor Control
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DOI：
10.1152/jn.90324.2008
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发表时间：
2009-07-01
影响因子：
2.5
通讯作者：
Todorov, Emanuel
中科院分区：
文献类型：
--
作者：
Valero-Cuevas, Francisco J.;Venkadesan, Madhusudhan;Todorov, Emanuel
[10]李晓梅，李晓梅，李晓梅.肌肉激活的结构性变化支持运动控制的最小干预原则。J Neurophysiol 102：59-68，2009.首次发表于2009年4月15日; doi：10.1152/jn.90324.2008。结构化运动变异的大量观察表明，感觉运动系统优先控制任务相关的参数，而允许任务无关的波动。优化模型表明，以这种方式控制冗余的肌肉骨骼系统满足任务需求，同时最大限度地减少控制工作。虽然这一系列的调查一直非常富有成效，但数据主要是行为的，没有直接的生理证据表明肌肉或神经活动的水平。此外，生物力学耦合、信号依赖性噪声和试验间变异性的替代原因混淆了行为研究。在这里，我们解决这些困惑，并提出证据表明，神经系统优先控制肌肉水平上的任务相关参数。我们要求受试者产生规定的恒定或随时间变化的幅度垂直指尖力矢量，同时保持恒定的手指姿势。在这项任务中，我们同时记录了所有七个食指肌肉的肌内肌电图（EMG）。实验设计和选择性的细钢丝肌肉记录允许我们解释给定EMG信号的指尖力的方差的91%的中位数。通过分析七维肌电信号空间中的肌肉协调性，我们发现任务相关子空间中的每维方差始终小于任务无关子空间。这第一个直接的生理证据上的肌肉水平优先控制的任务相关的参数强烈建议使用的神经控制策略兼容的原则，最小的干预。此外，在所有七个维度上，差异都是不可忽视的，这与肌肉激活模式由少量协同作用组成的观点不一致。
Valero-Cuevas FJ, Venkadesan M, Todorov E. Structured variability of muscle activations supports the minimal intervention principle of motor control. J Neurophysiol 102: 59-68, 2009. First published April 15, 2009; doi: 10.1152/jn.90324.2008. Numerous observations of structured motor variability indicate that the sensorimotor system preferentially controls task-relevant parameters while allowing task-irrelevant ones to fluctuate. Optimality models show that controlling a redundant musculo-skeletal system in this manner meets task demands while minimizing control effort. Although this line of inquiry has been very productive, the data are mostly behavioral with no direct physiological evidence on the level of muscle or neural activity. Furthermore, biomechanical coupling, signal-dependent noise, and alternative causes of trial-to-trial variability confound behavioral studies. Here we address those confounds and present evidence that the nervous system preferentially controls task-relevant parameters on the muscle level. We asked subjects to produce vertical fingertip force vectors of prescribed constant or time-varying magnitudes while maintaining a constant finger posture. We recorded intramuscular electromyograms (EMGs) simultaneously from all seven index finger muscles during this task. The experiment design and selective fine-wire muscle recordings allowed us to account for a median of 91% of the variance of fingertip forces given the EMG signals. By analyzing muscle coordination in the seven-dimensional EMG signal space, we find that variance-per-dimension is consistently smaller in the task-relevant subspace than in the task-irrelevant subspace. This first direct physiological evidence on the muscle level for preferential control of task-relevant parameters strongly suggest the use of a neural control strategy compatible with the principle of minimal intervention. Additionally, variance is nonnegligible in all seven dimensions, which is at odds with the view that muscle activation patterns are composed from a small number of synergies.