Guiding multiple muscles and joints without redundancy problems: the principle of minimal interaction

这项研究计划的目的是缩小对神经系统以连贯和特定于任务的方式控制多个肌肉和身体自由度的能力的基本原理的理解上的差距。在前期NSERC资助研究的基础上，成功验证并进一步发展了电机控制的门限控制理论。这一理论应用于涉及全身的动作，认为多个骨骼肌的肌电活动是通过比较身体的实际构型(Q)和大脑根据任务需求修改的内部几何图像或参照物(R)构型而产生的。这些构型之间的差异可以被认为是影响人体所有骨骼肌肌电活动的一个全球性因素。局部生物力学和神经生理学因素(例如，自体和异源反射)与全球因素相结合，使肌肉EMG模式多样化。还假设，为了产生运动动作，神经系统移动适当效应器(例如手)的阈值(虚拟)位置。作为回应，新出现的神经和肌肉活动倾向于在由内部和外部约束定义的限制内，最小化效应器的实际位置和虚拟位置之间的差异。神经肌肉系统的每个元素可能参与也可能不参与动作，这取决于它缩小效应器虚拟位置和实际位置之间差异的能力(S)。这些想法为控制多个肌肉和身体部分的不适定冗余问题提供了解决方案。目前的研究方案旨在测试这些新想法的适用性，首先是不同的手腕手势，其次是与从坐到站和走路的转变相关的一系列动作。测试将包括对这些动作的实验分析和数学建模。该项目不仅有助于理解运动控制的基本原理，还有助于设计假肢和机器人中的多关节假肢。

The aim of this research program is to diminish the gap in the understanding of the basic principles underlying the ability of the nervous system to control multiple muscles and degrees of freedom of the body in a coherent and task-specific way. Based on the previous research funded by NSERC, we successfully verified and further developed the threshold control theory of motor control. Applied to actions involving the whole body, this theory suggests that the electromyographic (EMG) activity of multiple skeletal muscles emerges from the comparison of the actual configuration (Q) of the body with its internal geometric image or referent (R) configuration modified by the brain according to task demands. The difference between these configurations can be considered as a global factor influencing the EMG activity of all skeletal muscles of the body. Local biomechanical and neurophysiological factors (e.g., autogenic and heterogenic reflexes) combined with the global factor diversify muscular EMG patterns. It was also assumed that, to produce a motor action, the nervous system shifts the threshold (virtual) position of an appropriate effector (e.g. the hand). In response, the emerging neural and muscular activity tends to minimize the difference between the actual and the virtual position of the effector, in the limits defined by internal and external constrains. Each element of the neuromuscular system may or may not be involved in the action depending on its ability to diminish the difference between the virtual and the actual position of the effector(s). These ideas offer a solution to the ill-posed redundancy problem in the control of multiple muscles and body segments. The present research proposal is designed to test the applicability of these new ideas to the production, first, of different hand-wrist gestures and, second, to a sequence of actions associated with the transition from sitting to standing and walking. Testing will involve both experimental analysis and mathematical modeling of these actions. The project may help not only in the understanding of the basic principles of motor control but also in designing muti-joint artificial limbs in prosthetics and robotics.