Section for Computational Sensomotorics, Department of Cognitive Neurology, Hertie Institute for Clinical Brain Research, Frondsbergstrasse 23, 72070, Tübingen, Germany.
Exp Brain Res. 2012 May;218(3):419-31. doi: 10.1007/s00221-012-3030-y. Epub 2012 Feb 25.
Previous investigations showed that kinematics and muscle activity associated with natural whole-body movements along the gravity direction present modular organizations encoding specific aspects relative to both the motor plans and the motor programmes underlying movement execution. It is, however, still unknown whether such modular structures characterize also the reverse movements, when the displacement of a large number of joints is required to take the whole body back to a standing initial posture. To study what motor patterns are conserved across the reversal of movement direction, principal component analysis and non-negative matrix factorization were therefore applied, respectively, to the time series describing the temporal evolution of the elevation angles associated with all the body links and to the electromyographic signals of both natural and reverse whole-body movements. Results revealed that elevation angles were highly co-varying in time and that despite some differences in the global parameters characterizing the different movements (indicating differences in high-level variable associated with the selected motor plans), the level of joint co-variation did not change across movement direction. In contrast, muscle organization of the forward whole-body pointing tasks was found to be different with respect to that characterizing the reverse movements. Such results agree with previous findings, according to which the central nervous system exploits, dependently on the direction of motion, different motor plans for the execution of whole-body movements. However, in addition, this study shows how such motor plans are translated into different muscle strategies that equivalently assure a high level of co-variation in the joint space.
先前的研究表明，与沿重力方向进行的自然全身运动相关的运动学和肌肉活动呈现出模块化组织，这些组织分别对运动执行的运动计划和运动程序的特定方面进行编码。然而，当需要大量关节的位移才能使整个身体回到初始站立姿势时，这种模块化结构是否也存在于反向运动中仍然未知。为了研究在运动方向反转时哪些运动模式是守恒的，因此分别对描述与所有身体关节相关的提升角度随时间的演变的时间序列以及自然和反向全身运动的肌电图信号进行了主成分分析和非负矩阵分解。结果表明，提升角度在时间上高度相关，尽管不同运动的全局参数（表示与所选运动计划相关的高级变量的差异）存在一些差异，但关节的协同变化程度并没有随着运动方向的改变而改变。相比之下，正向全身指向任务的肌肉组织与反向运动的肌肉组织不同。这些结果与之前的发现一致，根据这些发现，中枢神经系统根据运动方向，利用不同的运动计划来执行全身运动。然而，除此之外，这项研究还展示了这些运动计划如何转化为不同的肌肉策略，这些策略同样确保了关节空间的高度协同变化。
