Research Project for Motor Control, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-ku, Tokyo, Japan.
Cerebellum. 2012 Jun;11(2):426-33. doi: 10.1007/s12311-012-0370-x.
We propose a new method to provide a functional interpretation of motor commands (i.e., muscle activities) and their relationship to movement kinematics. We evaluated our method by analyzing the motor commands of normal controls and patients with cerebellar disorders for visually guided tracking movement of the wrist joint. Six control subjects and six patients with cerebellar disorders participated in this study. We asked the subjects to perform visually guided smooth tracking movement of the wrist joint with a manipulandum, and recorded the movements of the wrist joint and activities of the four wrist prime movers with surface electrodes. We found a symmetric relationship between the second-order linear equation of motion for the wrist joint and the linear sum of activities of the four wrist prime movers. The symmetric relationship determined a set of parameters to characterize the muscle activities and their similarity to the components of movement kinematics of the wrist joint. We found that muscle activities of the normal controls encoded both the velocity and the position of the moving target, resulting in precise tracking of the target. In contrast, muscle activities of the cerebellar patients were characterized by a severer impairment for velocity control and more dependence on position control, resulting in poor tracking of the smoothly moving target with many step-like awkward movements. Our results suggest that the cerebellum plays an important role in the generation of motor commands for smooth velocity and position control.
我们提出了一种新的方法，用于提供对运动指令（即肌肉活动）及其与运动运动学关系的功能解释。我们通过分析正常对照者和小脑障碍患者的运动指令来评估我们的方法，这些患者进行了视觉引导的腕关节跟踪运动。六名正常对照者和六名小脑障碍患者参加了这项研究。我们要求受试者用操纵器进行视觉引导的腕关节平滑跟踪运动，并使用表面电极记录腕关节的运动和四个腕部主要推动者的活动。我们发现腕关节二阶线性运动方程与四个腕部主要推动者活动的线性和之间存在对称关系。这种对称关系确定了一组参数，用于描述肌肉活动及其与腕关节运动运动学成分的相似性。我们发现，正常对照者的肌肉活动既编码了运动目标的速度，也编码了位置，从而实现了对目标的精确跟踪。相比之下，小脑障碍患者的肌肉活动在速度控制方面受到更严重的损害，对位置控制的依赖性更大，导致对平滑移动目标的跟踪效果不佳，出现许多步状笨拙运动。我们的结果表明，小脑在平滑速度和位置控制的运动指令产生中发挥着重要作用。
