Are complex control signals required for human arm movement?
Are complex control signals required for human arm movement?
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DOI：
10.1152/jn.1998.79.3.1409
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发表时间：
1998-03-01
影响因子：
2.5
通讯作者：
Laboissière, R
中科院分区：
文献类型：
--
作者：
Gribble, PL;Ostry, DJ;Laboissière, R
有人提出，自愿的人类手臂运动的控制信号有一个“复杂的”非单调的时变形式，并提供了一些实证研究结果，以支持这一想法。在本文中，我们解决了三个这样的调查结果使用模型的两个关节臂运动的基础上的lambda版本的平衡点假设。该模型包括六个单关节和双关节肌肉，反射，建模控制。信号、肌肉特性和肢体动力学。首先，我们解决的要求，“复杂”的平衡轨迹需要考虑到非单调的联合阻抗模式在多关节运动。使用恒定速率的变化，在神经指定的平衡的肢体和恒定的cocontraction命令，我们得到的模式，预测关节僵硬在模拟多关节运动，匹配的非单调模式的经验报告。然后，我们使用由Gomi和Kawato提出的算法，从模拟的刚度，粘度和肢体运动学计算一个假设的平衡轨迹。就像Gomi和Kawato报告的那样，所得到的轨迹是非单调的，首先领先然后滞后于肢体的位置。其次，我们解决的要求，高水平的刚度时，需要产生快速的单关节运动简单的平衡转移。我们比较经验测量的刚度在快速的单关节运动与预测刚度的运动产生的使用恒定速率的平衡位移和恒定的cocontraction命令。单关节运动模拟在一些速度，和程序使用的班尼特估计刚度如下。我们发现，当cocontraction命令的大小按比例缩放的运动速度，模拟关节刚度随运动速度的方式与班尼特报告的。第三，我们解决了相关的索赔，非单调平衡的转变需要产生快速的单关节运动。使用恒定速率的平衡转移和恒定的cocontraction命令，快速单关节运动的外部扭矩的存在下进行模拟。我们使用Latash和Gottlieb报告的程序来计算运动过程中模拟扭矩和角度测量的假设平衡轨迹。正如在Latash和Gottlieb，一个非单调的功能，即使在模拟中使用的控制信号是恒定速率的变化，在平衡位置的肢体。本论文提出的“简单”平衡轨迹与Gomi和Kawato以及Latash和Gottlieb使用的程序所得出的平衡轨迹之间的差异来自于他们使用的简化的力生成模型。
It has been proposed that the control signals underlying voluntary human arm movement have a "complex" nonmonotonic time-varying form, and a number of empirical findings have been offered in support of this idea. In this paper, we address three such findings using a model of two-joint arm motion based on the lambda version of the equilibrium-point hypothesis. The model includes six one-and two-joint muscles, reflexes, modeled control. signals, muscle properties, and limb dynamics. First, we address the claim that "complex" equilibrium trajectories are required to account for nonmonotonic joint impedance patterns observed during multijoint movement. Using constant-rate shifts in the neurally specified equilibrium of the limb and constant cocontraction commands, we obtain patterns of predicted joint stiffness during simulated multijoint movements that match the nonmonotonic patterns reported empirically. We then use the algorithm proposed by Gomi and Kawato to compute a hypothetical equilibrium trajectory from simulated stiffness, viscosity, and Limb kinematics. Like that reported by Gomi and Kawato, the resulting trajectory was nonmonotonic, first leading then lagging the position of the limb. Second, we address the claim that high levels of stiffness are required to generate rapid single-joint movements when simple equilibrium shifts are used. We compare empirical measurements of stiffness during rapid single-joint movements with the predicted stiffness of movements generated using constant-rate equilibrium shifts and constant cocontraction commands. Single-joint movements are simulated at a number of speeds, and the procedure used by Bennett to estimate stiffness is followed. We show that when the magnitude of the cocontraction command is scaled in proportion to movement speed, simulated joint stiffness varies with movement speed in a manner comparable with that reported by Bennett. Third, we address the related claim that nonmonotonic equilibrium shifts are required to generate rapid single-joint movements. Using constant-rate equilibrium shifts and constant cocontraction commands, rapid single-joint movements are simulated in the presence of external torques. We use the procedure reported by Latash and Gottlieb to compute hypothetical equilibrium trajectories from simulated torque and angle measurements during movement. As in Latash and Gottlieb, a nonmonotonic function is obtained even though the control signals used in the simulations are constant-rate changes in the equilibrium position of the limb. Differences between the "simple" equilibrium trajectory proposed in the present paper and those that are derived from the procedures used by Gomi and Kawato and Latash and Gottlieb arise from their use of simplified models of force generation.