Patterns of hypermetria and terminal cocontraction during point-to-point movements demonstrate independent action of trajectory and postural controllers.
Patterns of hypermetria and terminal cocontraction during point-to-point movements demonstrate independent action of trajectory and postural controllers.
复制标题
点对点运动期间的远视和终末收缩模式证明了轨迹和姿势控制器的独立作用。
DOI：
10.1152/jn.00763.2010
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发表时间：
2011
影响因子：
2.5
通讯作者：
Asnani,Supriya
中科院分区：
文献类型：
--
作者：
Scheidt,RobertA;Ghez,Claude;Asnani,Supriya
我们研究了肘部肌肉活动和运动学，以确定受试者如何结合联合收割机基本控制动作，在执行运动与一个和两个轨迹段。在达到，科目作出了快速肘关节屈曲到视觉目标，然后稳定的肢体与低或更高水平的肘屈肌/伸肌的共同活动（CoA），这是由目标直径提示。光标直径提供实际肌肉CoA的实时生物反馈。在反向时，肢体在目标内反向并以最小CoA返回原点。我们以前报道过，受试者在第一次学会准确到达同一目标后，在尝试逆转时会超过目标。在这里，我们测试的假设，这种hypermetria的结果，因为逆转co-opt从前面的训练达到的初始前馈控制动作，从而无法解释任务相关的肢体阻抗的变化引起的屈肌/伸肌协同活动的差异，作为目标的收购（更高的达到比逆转）。肘关节CoA的指示增加开始于中段，从而增加肘关节阻抗并减少低CoA运动中存在的瞬态振荡。运动开始时，屈肌肌电图单独增加。测试逆转纳入了先前达到的初始激动剂活性，但没有增加靶点的协同活性，从而导致过冲。此外，我们观察到升高的协同性反转后返回到原点，即使在达到的协同性是集中在目标。这些发现驳斥了大脑必然会调用不同的单一控制动作来达到和逆转同一目标的观点。相反，到达和反转共享一个共同的控制动作，启动朝向目标的轨迹，以及另一个稍后的控制动作，终止运动并使肢体稳定在其最终的休息姿势，这在两个任务中是不同的。
We examined elbow muscle activities and movement kinematics to determine how subjects combine elementary control actions in performing movements with one and two trajectory segments. In reaching, subjects made a rapid elbow flexion to a visual target before stabilizing the limb with either a low or a higher level of elbow flexor/extensor coactivity (CoA), which was cued by target diameter. Cursor diameter provided real-time biofeedback of actual muscle CoA. In reversing, the limb was to reverse direction within the target and return to the origin with minimal CoA. We previously reported that subjects overshoot the goal when attempting a reversal after first having learned to reach accurately to the same target. Here we test the hypothesis that this hypermetria results because reversals co-opt the initial feedforward control action from the preceding trained reach, thereby failing to account for task-dependent changes in limb impedance induced by differences in flexor/extensor coactivity as the target is acquired (higher in reaching than reversing). Instructed increases in elbow CoA began mid-reach, thus increasing elbow impedance and reducing transient oscillations present in low CoA movments. Flexor EMG alone increased at movement onset. Test reversals incorporated the initial agonist activity of previous reaches but not the increased coactivity at the target, thus leading to overshoot. Moreover, we observed elevated coactivity in reversals upon returning to the origin even though coactivity in reaching was centered at the goal target. These findings refute the idea that the brain necessarily invokes distinct unitary control actions for reaches and reversals made to the same target. Instead, reaches and reversals share a common control action that initiates trajectories toward their target and another later control action that terminates movement and stabilizes the limb about its final resting posture, which differs in the two tasks.