Coordinating movement at two joints: A principle of linear covariance
Coordinating movement at two joints: A principle of linear covariance
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DOI：
10.1152/jn.1996.75.4.1760
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发表时间：
1996-04-01
影响因子：
2.5
通讯作者：
Corcos, D
中科院分区：
文献类型：
--
作者：
Gottlieb, GL;Song, QL;Corcos, D
1.六名受试者在矢状面上，在三个角度距离内快速完成肘部或肩部的单关节屈曲。运动终点的定位只需要屈曲一个单一的“焦点”关节，对另一个“非焦点”关节没有任何外部的机械约束。三名受试者在两个目标之间进行了另一系列的运动，同时沿着不同的路径移动，其中两个关节都是弯曲的。我们比较了两个关节产生的扭矩模式。对于单关节运动，它们都是双相脉冲，先加速后减速。在整个运动过程中，单个关节运动的非焦点关节处的扭矩与焦点关节处的扭矩非常接近线性成正比。肘部扭矩和肩部扭矩相差一个线性比例常数，几乎同时经历极值和过零点。相比之下，在受试者被明确指示使用他们不会自然使用的手部路径的运动中，线性关节间扭矩比例规则不适用。这表明，当我们希望沿着两个目标之间的路径移动时，该路径不是由线性扭矩共同变化产生的，我们能够随意修改该规则。我们推测，两个关节上扭矩模式的线性、动态协变可能是减少神经系统在自然选择的路径上执行无约束肢体运动时必须独立控制的自由度的重要原则。
1. Six subjects performed fast, ''single-joint'' flexions of either the elbow or shoulder over three angular distances in a sagittal plane. Movement endpoints were located to require flexion of only a single, ''focal'' joint, without any external, mechanical constraint on the other, ''nonfocal'' joint. Three subjects performed another series of movements between two targets while moving along different paths and in which both joints were flexed.2. We compared the torque patterns that were produced at the two joints. For single-joint movements, they were both biphasic pulses that accelerated and then decelerated the limb.3. The torque at the nonfocal joint of a single joint movement was very close to linearly proportional to that at the focal joint throughout the movement. Elbow and shoulder torques differed by a linear scaling constant and went through extrema and zero crossings almost simultaneously.4. in contrast, during movements in which subjects were explicitly instructed to use a hand path they would not naturally use, the linear interjoint torque scaling rule did not apply. This demonstrated that when we wish to move along a path between two targets that is not produced by linear torque covariation, we are able to modify that rule at will.5. We speculate that linear, dynamic covariation of the torque patterns across two joints may be an important principle for reducing the number of degrees of freedom that the nervous system must independently control in performing unconstrained limb movements over naturally chosen paths.