Aflalo Tyson N, Graziano Michael S A
Department of Psychology, Princeton University, Princeton, New Jersey 08544-1010, USA.
J Neurosci. 2007 Mar 14;27(11):2760-80. doi: 10.1523/JNEUROSCI.3147-06.2007.
The activity of single neurons in the monkey motor cortex was studied during semi-naturalistic, unstructured arm movements made spontaneously by the monkey and measured with a high resolution three-dimensional tracking system. We asked how much of the total neuronal variance could be explained by various models of neuronal tuning to movement. On average, tuning to the speed of the hand accounted for 1% of the total variance in neuronal activity, tuning to the direction of the hand in space accounted for 8%, a more complex model of direction tuning, in which the preferred direction of the neuron rotated with the starting position of the arm, accounted for 13%, tuning to the final position of the hand in Cartesian space accounted for 22%, and tuning to the final multijoint posture of the arm accounted for 36%. One interpretation is that motor cortex neurons are significantly tuned to many control parameters important in the animal's repertoire, but that different control parameters are represented in different proportion, perhaps reflecting their prominence in everyday action. The final posture of a movement is an especially prominent control parameter although not the only one. A common mode of action of the monkey arm is to maintain a relatively stable overall posture while making local adjustments in direction during performance of a task. One speculation is that neurons in motor cortex reflect this pattern in which direction tuning predominates in local regions of space and postural tuning predominates over the larger workspace.
在猴子进行半自然、无结构的自发手臂运动期间，研究了其运动皮层单个神经元的活动，并使用高分辨率三维跟踪系统进行测量。我们探讨了神经元对运动的各种调谐模型能够解释神经元总方差的多少。平均而言，对手部速度的调谐占神经元活动总方差的1%，对空间中手部方向的调谐占8%，一种更复杂的方向调谐模型（其中神经元的偏好方向随手臂起始位置旋转）占13%，对笛卡尔空间中手部最终位置的调谐占22%，对手臂最终多关节姿势的调谐占36%。一种解释是，运动皮层神经元显著调谐于动物行为中许多重要的控制参数，但不同的控制参数以不同比例呈现，这可能反映了它们在日常动作中的突出程度。运动的最终姿势是一个特别突出的控制参数，尽管不是唯一的。猴子手臂的一种常见动作模式是在执行任务期间保持相对稳定的整体姿势，同时在方向上进行局部调整。一种推测是，运动皮层中的神经元反映了这种模式，即方向调谐在局部空间区域占主导，而姿势调谐在更大的工作空间中占主导。
