Ajemian Robert, Green Andrea, Bullock Daniel, Sergio Lauren, Kalaska John, Grossberg Stephen
McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Neuron. 2008 May 8;58(3):414-28. doi: 10.1016/j.neuron.2008.02.033.
Do neurons in primary motor cortex encode the generative details of motor behavior, such as individual muscle activities, or do they encode high-level movement attributes? Resolving this question has proven difficult, in large part because of the sizeable uncertainty inherent in estimating or measuring the joint torques and muscle forces that underlie movements made by biological limbs. We circumvented this difficulty by considering single-neuron responses in an isometric task, where joint torques and muscle forces can be straightforwardly computed from limb geometry. The response for each neuron was modeled as a linear function of a "preferred" joint torque vector, and this model was fit to individual neural responses across variations in limb posture. The resulting goodness of fit suggests that neurons in motor cortex do encode the kinetics of motor behavior and that the neural response properties of "preferred direction" and "gain" are dual components of a unitary response vector.
初级运动皮层中的神经元是编码运动行为的生成细节，比如单个肌肉活动，还是编码高级运动属性？事实证明，解决这个问题很困难，很大程度上是因为在估计或测量生物肢体运动背后的关节扭矩和肌肉力量时存在相当大的不确定性。我们通过考虑等长任务中的单神经元反应规避了这一困难，在等长任务中，可以根据肢体几何结构直接计算关节扭矩和肌肉力量。每个神经元的反应被建模为一个“偏好”关节扭矩向量的线性函数，并且这个模型针对肢体姿势变化时的个体神经反应进行拟合。所得的拟合优度表明，运动皮层中的神经元确实编码了运动行为的动力学，并且“偏好方向”和“增益”的神经反应特性是单一反应向量的两个组成部分。
