Desmurget M, Gréa H, Prablanc C
Emory University School of Medicine, Department of Neurology, Atlanta, GA 30322, USA.
Exp Brain Res. 1998 Apr;119(4):511-6. doi: 10.1007/s002210050367.
The question of knowing how the nervous system transforms a desired position and orientation of the hand into a set of arm and forearm angles has been widely addressed during the last few decades. Despite this fact, it still remains unclear as to whether a unique posture of the arm is associated with every location and orientation of the hand in space. The main objective of the present study a was to address this question. To this end, we studied a prehension task requiring human subjects to reach and grasp a cylindrical object presented at different locations, along variable orientations. In contrast to previous investigations, we considered the influence of the initial position of the hand. Results showed that the posture of the arm: (1) varied systematically as a function of the movement starting point; (2) was stereotyped for a particular subject given a configuration of the object and a movement starting location; (3) was altered at both the distal and proximal levels when the orientation of the object was changed; (4) was similarly influenced by the experimental factors in all the subjects, except one. When considered together, the previous results support three main conclusions: First, the nervous system solves the joint redundancy problem using fixed strategies. Second, these fixed strategies do not provide a single correspondence between hand configuration and arm posture. Third, the position and orientation of the hand in space are unlikely to be controlled through separate independent neural pathways.
在过去几十年里，神经系统如何将手部期望的位置和方向转化为一组手臂和前臂角度的问题已得到广泛探讨。尽管如此，手臂的独特姿势是否与手部在空间中的每个位置和方向相关，仍不清楚。本研究的主要目的是解决这个问题。为此，我们研究了一项抓握任务，要求人类受试者伸手去抓握放置在不同位置、具有不同方向的圆柱形物体。与之前的研究不同，我们考虑了手部初始位置的影响。结果表明，手臂的姿势：(1) 作为运动起始点的函数而系统地变化；(2) 对于给定物体配置和运动起始位置的特定受试者而言是刻板的；(3) 当物体方向改变时，在远端和近端水平都会发生改变；(4) 除一名受试者外，所有受试者的实验因素对其影响相似。综合考虑，先前的结果支持三个主要结论：第一，神经系统使用固定策略解决关节冗余问题。第二，这些固定策略并未在手部配置和手臂姿势之间提供单一对应关系。第三，手部在空间中的位置和方向不太可能通过单独独立的神经通路来控制。
