Zhou Tao, Solnik Stanislaw, Wu Yen-Hsun, Latash Mark L
Department of Kinesiology, Rec.Hall-267, The Pennsylvania State University, University Park, PA, 16802, USA.
Exp Brain Res. 2014 Dec;232(12):3847-59. doi: 10.1007/s00221-014-4059-x. Epub 2014 Aug 24.
We tested several predictions of a recent theory that combines the ideas of control with referent configurations, hierarchical control, and the uncontrolled manifold (UCM) hypothesis. In particular, we tested a hypothesis that unintentional changes in hand coordinate can happen following a long-lasting transient perturbation. The subjects grasped a handle with the right hand, occupied an initial position against a bias force produced by the HapticMaster robot, and then tried not to react to changes in the robot-produced force. Changes in the force were smooth and transient; they always ended with the same force as the bias force. The force-change amplitude and the time the force was kept at the new level (dwell time) varied across conditions. After the transient force change was over, the handle rested in a position that differed significantly from the initial position. The amplitude of this unintentional movement increased with the amplitude of transient force change and with the dwell time. In the new position, the across-trials joint configuration variance was mostly confined to a subspace compatible with the average handle coordinate and orientation (the UCMs for these variables). We view these results as the first experimental support for the hypothesis on back-coupling between the referent and actual body configurations during multi-joint actions. The results suggest that even under the instruction "not to react to transient force changes," the subjects may be unable to prevent unintentional drift of the referent configuration. The structure of joint configuration variance after such movements was similar to that in earlier reports on joint configuration variance after intentional movements. We conclude that the intentional and unintentional movements are products of a single neural system that can lead to intentional and unintentional shifts of the referent body configuration.
我们对最近一种理论的几个预测进行了测试，该理论将控制概念与参考构型、层次控制和非控制流形（UCM）假设相结合。具体而言，我们测试了一个假设，即长时间的瞬态扰动后，手部坐标可能会发生无意的变化。受试者用右手握住一个手柄，在触觉主机器人产生的偏置力作用下占据初始位置，然后试图不对手臂产生的力的变化做出反应。力的变化是平滑且瞬态的；它们总是以与偏置力相同的力结束。力变化的幅度以及力保持在新水平的时间（停留时间）在不同条件下有所不同。瞬态力变化结束后，手柄停留在与初始位置显著不同的位置。这种无意运动的幅度随着瞬态力变化的幅度和停留时间的增加而增加。在新位置，试验间关节构型方差大多局限于与平均手柄坐标和方向兼容的子空间（这些变量的UCM）。我们将这些结果视为对多关节动作期间参考构型与实际身体构型之间反向耦合假设的首个实验支持。结果表明，即使在“不对手臂产生的力的变化做出反应”的指令下，受试者可能也无法防止参考构型的无意漂移。这种运动后关节构型方差的结构与早期关于有意运动后关节构型方差的报告相似。我们得出结论，有意和无意运动是单一神经系统的产物，该系统可导致参考身体构型的有意和无意偏移。
