Mattos D, Schöner G, Zatsiorsky V M, Latash M L
Biomechanics and Movement Science Program, University of Delaware, Newark, DE, United States; Program in Occupational Therapy, Washington University, Saint Louis, MO, United States; Department of Kinesiology, The Pennsylvania State University, University Park, PA, United States.
Institut für Neuroinformatik, Rühr University Bochum, Bochum, Germany.
Neuroscience. 2015 Dec 3;310:600-15. doi: 10.1016/j.neuroscience.2015.09.071. Epub 2015 Oct 3.
Our main goal was to test a hypothesis that transient changes in performance of a steady-state task would result in motor equivalence. We also estimated effects of visual feedback on the amount of reorganization of motor elements. Healthy subjects performed two variations of a four-finger pressing task requiring accurate production of total pressing force (F TOT) and total moment of force (M TOT). In the Jumping-Target task, a sequence of target jumps required transient changes in either F TOT or M TOT. In the Step-Perturbation task, the index finger was lifted by 1cm for 0.5s leading to a change in both F TOT and M TOT. Visual feedback could have been frozen for one of these two variables in both tasks. Deviations in the space of finger modes (hypothetical commands to individual fingers) were quantified in directions of unchanged F TOT and M TOT (motor equivalent - ME) and in directions that changed F TOT and M TOT (non-motor equivalence - nME). Both the ME and nME components increased when the performance changed. After transient target jumps leading to the same combination of F TOT and M TOT, the changes in finger modes had a large residual ME component with only a very small nME component. Without visual feedback, an increase in the nME component was observed without consistent changes in the ME component. Results from the Step-Perturbation task were qualitatively similar. These findings suggest that both external perturbations and purposeful changes in performance trigger a reorganization of elements of an abundant system, leading to large ME change. These results are consistent with the principle of motor abundance corroborating the idea that a family of solutions is facilitated to stabilize values of important performance variables.
我们的主要目标是检验一个假设，即稳态任务表现的短暂变化会导致运动等效性。我们还估计了视觉反馈对运动元素重组量的影响。健康受试者执行了一项四指按压任务的两种变体，要求精确产生总按压力（FTOT）和总力矩（MTOT）。在跳跃目标任务中，一系列目标跳跃要求FTOT或MTOT发生短暂变化。在阶跃扰动任务中，食指被抬起1厘米持续0.5秒，导致FTOT和MTOT都发生变化。在这两项任务中，视觉反馈可能针对这两个变量之一被冻结。在FTOT和MTOT不变的方向（运动等效 - ME）以及FTOT和MTOT发生变化的方向（非运动等效 - nME）上，对手指模式空间（对各个手指的假设指令）中的偏差进行了量化。当表现发生变化时，ME和nME分量都会增加。在导致相同FTOT和MTOT组合的短暂目标跳跃之后，手指模式的变化具有很大的残余ME分量，只有非常小的nME分量。在没有视觉反馈的情况下，观察到nME分量增加，而ME分量没有一致的变化。阶跃扰动任务的结果在定性上相似。这些发现表明，外部扰动和表现的有意变化都会触发丰富系统元素的重组，导致ME发生很大变化。这些结果与运动丰富性原则一致，证实了这样一种观点，即有助于稳定重要表现变量值的一系列解决方案。
