Bizzi E, Accornero N, Chapple W, Hogan N
J Neurosci. 1984 Nov;4(11):2738-44. doi: 10.1523/JNEUROSCI.04-11-02738.1984.
One hypothesis for the generation of spatially oriented arm movements by the central nervous system is that a desired joint position is determined by the ratio of the tensions of agonist and antagonist muscles. According to this hypothesis, the transition between equilibrium states should be solely a function of the contraction time of the motor units and the mechanical properties of the arm. We tested this hypothesis in intact and deafferented rhesus monkeys by holding the forearm and measuring the accelerative transient after release of the forearm and by directly measuring the time course of the increase in torque during the movement. Both methods indicated an average time of 400 msec for attaining peak torque in a movement with a duration of 700 msec. In addition, by displacing the arm from its normal trajectory during the movement, we observed that the arm returned neither to the initial nor to the final equilibrium positions, but to points intermediate between them. We conclude that the processes underlying trajectory formation must be more complex than a simple switch between one equilibrium position and another.
中枢神经系统产生空间定向手臂运动的一种假设是，期望的关节位置由主动肌和拮抗肌的张力比决定。根据这一假设，平衡状态之间的转换应该仅仅是运动单位收缩时间和手臂力学特性的函数。我们通过握住前臂并测量前臂释放后的加速瞬变，以及直接测量运动过程中扭矩增加的时间进程，在完整和去传入神经的恒河猴身上测试了这一假设。两种方法都表明，在持续700毫秒的运动中，达到峰值扭矩的平均时间为400毫秒。此外，通过在运动过程中将手臂从其正常轨迹上移开，我们观察到手臂既没有回到初始平衡位置，也没有回到最终平衡位置，而是回到了它们之间的中间点。我们得出结论，轨迹形成背后的过程一定比一个平衡位置和另一个平衡位置之间的简单切换更为复杂。
