Optimal control of redundant muscles in step-tracking wrist movements
Optimal control of redundant muscles in step-tracking wrist movements
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DOI：
10.1152/jn.00404.2005
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发表时间：
2005-12-01
影响因子：
2.5
通讯作者：
Wolpert, DM
中科院分区：
文献类型：
--
作者：
Haruno, M;Wolpert, DM
运动神经科学中的一个重要问题是神经系统如何控制冗余肌肉的时空激活模式以产生精确的运动。多余的肌肉不仅可能是我们动作灵活性的基础，而且还提出了一个具有挑战性的问题，即如何从大量可能的激活中选择特定的肌肉激活序列。在这里，我们建议，在确定冗余肌肉的最佳运动命令中，应考虑在运动命令中的噪声对任务完成的影响。我们提出了一个最佳控制模型的步骤跟踪手腕运动的冗余肌肉，最小化端点方差下的信号依赖性噪声。对人类和非人灵长类动物腕部运动的步迹跟踪为研究冗余肌肉运动的控制机制提供了详细的数据集。实验肌电数据可概括为两个显著特征：1）幅度分级肌电模式，即激动剂和拮抗剂爆发的活动时间随运动方向的改变而略有变化，只有活动幅度受到调制;和2）对激动剂和拮抗剂爆发所表现的运动方向的余弦调谐，以及肌肉激动剂的优选方向和其拉动方向之间的差异。此外，受试者经常超过目标也是一个重要的观察结果。我们证明，该模型不仅捕捉手腕肌肉的时空激活模式，但轨迹过冲。这表明，当招募多余的肌肉时，神经系统可能会优化肌肉之间的运动命令，以减少运动噪音的负面影响。
An important question in motor neuroscience is how the nervous system controls the spatiotemporal activation patterns of redundant muscles in generating accurate movements. The redundant muscles may not only underlie the flexibility of our movements but also pose the challenging problem of how to select a specific sequence of muscle activation from the huge number of possible activations. Here, we propose that noise in the motor command that has an influence on task achievement should be considered in determining the optimal motor commands over redundant muscles. We propose an optimal control model for step- tracking wrist movements with redundant muscles that minimizes the end- point variance under signal- dependent noise. Step- tracking wrist movements of human and nonhuman primates provide a detailed data set to investigate the control mechanisms in movements with redundant muscles. The experimental EMG data can be summarized by two eminent features: 1) amplitude- graded EMG pattern, where the timing of the activity of the agonist and antagonist bursts show slight variations with changes in movement directions, and only the amplitude of activity is modulated; and 2) cosine tuning for movement directions exhibited by the agonist and antagonist bursts, and the discrepancy found between a muscle's agonist preferred direction and its pulling direction. In addition, it is also an important observation that subjects often overshoot the target. We demonstrate that the proposed model captures not only the spatiotemporal activation patterns of wrist muscles but also trajectory overshooting. This suggests that when recruiting redundant muscles, the nervous system may optimize the motor commands across the muscles to reduce the negative effects of motor noise.