Clinical Neurophysiology Laboratories, Department of Neurology, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.
J Neurosci. 2011 Feb 9;31(6):1944-8. doi: 10.1523/JNEUROSCI.0056-10.2011.
During simultaneous generation of static and dynamic forces, motor cortical signals only predict the dynamic components, suggesting a key role in the coding of force changes. However, such a role is obscured by uncertainties regarding the representation of dynamic force signals in corticospinal outputs. We used transcranial magnetic stimulation (TMS) of the motor cortex in humans during a task that dissociated the direction of instantaneous net force and that of force derivative. The direction of TMS-evoked force outputs was closely associated with that of the force derivative, and had no relationship with that of the net force generated simultaneously, even though the magnitude of the instantaneous net force largely exceeded that of the force derivative. This observation supports the hypothesis that during dynamic force generation, the motor cortex and the corticospinal system assume a pivotal role in coding the direction of force changes, through selective recruitment of spinal motoneurons.
在同时产生静态和动态力时，运动皮层信号仅预测动态分量，这表明其在力变化的编码中起着关键作用。然而，由于皮质脊髓输出中动态力信号的表示存在不确定性，这种作用被掩盖了。我们在人类进行一项任务时使用经颅磁刺激（TMS）刺激运动皮层，该任务将瞬时净力的方向与力导数的方向分开。TMS 诱发的力输出的方向与力导数的方向密切相关，而与同时产生的净力的方向无关，尽管瞬时净力的大小大大超过力导数的大小。这一观察结果支持了这样一种假设，即在产生动态力时，运动皮层和皮质脊髓系统通过选择性募集脊髓运动神经元，在编码力变化的方向方面起着关键作用。
