Padoa-Schioppa Camillo, Li Chiang-Shan Ray, Bizzi Emilio
McGovern Institute for Brain Research, Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
J Neurophysiol. 2004 Jan;91(1):449-73. doi: 10.1152/jn.00876.2002. Epub 2003 Sep 10.
To execute visually guided reaching movements, the central nervous system (CNS) must transform a desired hand trajectory (kinematics) into appropriate muscle-related commands (dynamics). It has been suggested that the CNS might face this challenging computation by using internal forward models for the dynamics. Previous work in humans found that new internal models can be acquired through experience. In a series of studies in monkeys, we investigated how neurons in the motor areas of the frontal lobe reflect the movement dynamics and how their activity changes when monkeys learn a new internal model. Here we describe the results for the supplementary motor area (SMA-proper, or SMA). In the experiments, monkeys executed visually guided reaching movements and adapted to an external perturbing force field. The experimental design allowed dissociating the neuronal activity related to movement dynamics from that related to movement kinematics. It also allowed dissociating the changes related to motor learning from the activity related to motor performance (kinematics and dynamics). We show that neurons in SMA reflect the movement dynamics individually and as a population, and that their activity undergoes a variety of plastic changes when monkeys adapt to a new dynamic environment.
为了执行视觉引导的伸手动作，中枢神经系统（CNS）必须将期望的手部轨迹（运动学）转化为适当的与肌肉相关的指令（动力学）。有人提出，中枢神经系统可能通过使用动力学的内部前向模型来应对这一具有挑战性的计算。此前在人类身上的研究发现，新的内部模型可以通过经验习得。在一系列针对猴子的研究中，我们研究了额叶运动区域的神经元如何反映运动动力学，以及当猴子学习新的内部模型时它们的活动如何变化。在此，我们描述辅助运动区（真正的辅助运动区，或SMA）的研究结果。在实验中，猴子执行视觉引导的伸手动作并适应外部扰动力量场。实验设计使得能够将与运动动力学相关的神经元活动与与运动运动学相关的活动区分开来。它还使得能够将与运动学习相关的变化与与运动表现（运动学和动力学）相关的活动区分开来。我们表明，辅助运动区的神经元分别以及作为一个群体反映运动动力学，并且当猴子适应新的动态环境时，它们的活动会经历各种可塑性变化。
