Department of Organismal Biology and Anatomy, University of Chicago, Chicago, IL 60637, United States.
Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15213, United States.
Cereb Cortex. 2020 Sep 3;30(10):5400-5409. doi: 10.1093/cercor/bhaa120.
Motor commands for the arm and hand generally arise from the contralateral motor cortex, where most of the relevant corticospinal tract originates. However, the ipsilateral motor cortex shows activity related to arm movement despite the lack of direct connections. The extent to which the activity related to ipsilateral movement is independent from that related to contralateral movement is unclear based on conflicting conclusions in prior work. Here we investigate bilateral arm and hand movement tasks completed by two human subjects with intracortical microelectrode arrays implanted in the left hand and arm area of the motor cortex. Neural activity was recorded while they attempted to perform arm and hand movements in a virtual environment. This enabled us to quantify the strength and independence of motor cortical activity related to continuous movements of each arm. We also investigated the subjects' ability to control both arms through a brain-computer interface. Through a number of experiments, we found that ipsilateral arm movement was represented independently of, but more weakly than, contralateral arm movement. However, the representation of grasping was correlated between the two hands. This difference between hand and arm representation was unexpected and poses new questions about the different ways the motor cortex controls the hands and arms.
手臂和手部的运动指令通常来自对侧运动皮层，而大部分相关的皮质脊髓束起源于此。然而，尽管缺乏直接连接，同侧运动皮层仍显示出与手臂运动相关的活动。基于先前工作中相互矛盾的结论，同侧运动相关活动在多大程度上独立于对侧运动相关活动尚不清楚。在这里，我们研究了两位人类受试者在左手臂和手臂运动皮层区域植入颅内微电极阵列后完成的双侧手臂和手部运动任务。当他们试图在虚拟环境中进行手臂和手部运动时，记录了神经活动。这使我们能够量化与每个手臂的连续运动相关的运动皮层活动的强度和独立性。我们还研究了受试者通过脑机接口控制两只手臂的能力。通过一系列实验，我们发现，尽管同侧手臂运动的表现不如对侧手臂运动强，但它是独立于对侧手臂运动表现的。然而，双手的抓握表现是相关的。这种手和手臂表现之间的差异出人意料，提出了关于运动皮层控制手和手臂的不同方式的新问题。
