Coordinate frames for neuronal activities in the supplementary motor area, the premotor area and the primary motor cortex.

我们记录了初级运动皮层（Ml）和腹侧前运动皮层（PMv）神经元的活动，在猴子训练执行任务，分离的三个主要坐标框架的手腕运动：肌肉，腕关节，和一个外在的坐标框架。我们在Ml和PMv中发现了三种主要类型的神经元。第一种类型被称为“类外源性”。“这些神经元的活动似乎编码了空间运动的方向，而不依赖于产生运动的手腕肌肉活动或关节运动的模式。第二种类型被称为“类外增益调制”。这些神经元的活动似乎编码了空间运动的方向，但神经元活动的幅度（增益）取决于前臂的姿势。第三种类型被称为“肌肉样”，因为它们的活动与肌肉活动共同变化。PMv中的绝大多数定向调谐神经元被归类为“类外”（48/59，81%）。一个较小的组被归类为“具有增益调制的外源性样”（7/59，12%）。在Ml中，三种类型的神经元更平等地代表。我们的研究结果提出了可能性，Ml和PMV之间的皮层处理可能有助于外部和内部坐标系之间的感觉运动转换。最近的建模研究已经证明了这样一个过程的计算能力。

We recorded the activity of neurons in primary motor cortex (Ml) and ventral premotor cortex (PMv) in a monkey trained to perform a task which dissociates three major coordinate frames of wrist movement: muscle, wrist joint, and an extrinsic coordinate frame. We found three major types of neurons in Ml and PMv. The first type was termed "extrinsic-like." The activity of these neurons appeared to encode the direction of movement in space independent of the patterns of wrist muscle activity or joint movement that produced the movements. The second type was termed "extrinsic-like with gain modulation". The activity of these neurons appeared to encode the direction of movement in space, but the magnitude (gain) of neuronal activity depended on the posture of the forearm. The third type was termed "muscle-like" since their activity co-varied with muscle activity. The great majority of the directionally-tuned neurons in the PMv were classified as "extrinsic-like" (48/59, 81 %). A smaller group was classified as "extrinsic-like with gain modulation" (7/59, 12%). In Ml, the three types of neurons were more equally represented. Our results raise the possibility that cortical processing between Ml and PMv may contribute to a sensorimotor transformation between extrinsic and intrinsic coordinate frames. Recent modeling studies have demonstrated the computational plausibility of such a process.