Identification of neural feedback for upright stance in humans: stabilization rather than sway minimization.
Identification of neural feedback for upright stance in humans: stabilization rather than sway minimization.
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DOI：
10.1523/jneurosci.1013-11.2011
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发表时间：
2011-10-19
期刊：
影响因子：
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通讯作者：
Jeka JJ
中科院分区：
文献类型：
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作者：
Kiemel T;Zhang Y;Jeka JJ
运动控制的一个基本问题是如何确定特定行为的任务目标。在这里，我们通过分别识别人体姿势控制回路的肌肉骨骼和反馈组件来解决这个问题。18名受试者受到两种机械干扰(腰部和肩部水平从后面轻轻拉动)和一种感觉干扰(虚拟视觉场景的移动)的干扰。身体运动学通过腿部和躯干在矢状面上的角度来描述。肌肉的激活由脚踝和臀部的肌电信号描述，每个肌电信号被计算为给定关节处多个肌肉的整流肌电信号的加权和。机械扰动被用来识别反馈，反馈定义为从两个分段角度到两个EMG信号的映射。感官摄动被用来估计植物的机械模型中的参数，该模型被定义为从两个肌电信号到两个分段角度的映射。利用被控对象模型和最优控制理论，我们对一系列成本函数的辨识反馈和最优反馈进行了比较。确定的反馈类似于以接近最低的肌肉激活来稳定直立姿势的反馈，但与显著增加肌肉激活以减少身体重心或压力中心运动的反馈不一致。结果表明，减少摇摆的常见假设可能不适用于天生不稳定的肌肉骨骼系统。
A fundamental issue in motor control is how to determine the task goals for a given behavior. Here we address this question by separately identifying the musculoskeletal and feedback components of the human postural control loop. Eighteen subjects were perturbed by two mechanical perturbations (gentle pulling from behind at waist and shoulder levels) and one sensory perturbation (movement of a virtual visual scene). Body kinematics were described by the leg and trunk segment angles in the sagittal plane. Muscle activations were described by ankle and hip EMG signals, with each EMG signal computed as a weighted sum of rectified EMG signals from multiple muscles at the given joint. The mechanical perturbations were used to identify feedback, defined as the mapping from the two segment angles to the two EMG signals. The sensory perturbation was used to estimate parameters in a mechanistic model of the plant, defined as the mapping from the two EMG signals to the two segment angles. Using the plant model and optimal control theory, we compared identified feedback to optimal feedback for a range of cost functions. Identified feedback was similar to feedback that stabilizes upright stance with near-minimum muscle activation, but was not consistent with feedback that substantially increases muscle activation in order to reduce movements of the body's center of mass or center of pressure. The results suggest that the common assumption of reducing sway may not apply to musculoskeletal systems that are inherently unstable.