School of Sport, Exercise and Rehabilitation Sciences, Centre for Human Brain Health, University of Birmingham, Birmingham, United Kingdom.
Faculty of Physical Therapy and Sports Medicine, Rangsit University, Pathumthani, Thailand.
J Neurophysiol. 2021 Mar 1;125(3):875-886. doi: 10.1152/jn.00688.2020. Epub 2021 Feb 10.
Precise control of upper limb movements in response to external stimuli is vital to effectively interact with the environment. Accurate execution of bimanual movement is known to rely on finely orchestrated interhemispheric communication between the primary motor cortices (M1s). However, relatively little is known about the role of interhemispheric communication during sudden cancellation of prepared bimanual movement. The current study investigated the role of interhemispheric interactions during complete and partial cancellation of bimanual movement. In two experiments, healthy young human participants received transcranial magnetic stimulation to both M1s during a bimanual response inhibition task. The increased corticomotor excitability in anticipation of bimanual movement was accompanied by a release of inhibition from both M1s. After a stop cue, inhibition was reengaged onto both hemispheres to successfully cancel the complete bimanual response. However, when the stop cue signaled partial cancellation (stopping of one digit only), inhibition was reengaged with regard to the cancelled digit, but the responding digit representation was facilitated. This bifurcation in interhemispheric communication between M1s occurred 75 ms later in the more difficult condition when the nondominant, as opposed to dominant, hand was still responding. Our results demonstrate that interhemispheric communication is integral to response inhibition once a bimanual response has been prepared. Interestingly, M1-M1 interhemispheric circuitry does not appear to be responsible for the nonselective suppression of all movement components that has been observed during partial cancellation. Instead such interhemispheric communication enables uncoupling of bimanual response components and facilitates the selective initiation of just the required unimanual movement. We provide the first evidence that interhemispheric communication plays an important role during sudden movement cancellation of two-handed responses. Simultaneously increased inhibition onto both hemispheres assists with two-handed movement cancellation. However, this network is not responsible for the widespread suppression of motor activity observed when only one of the two hands is cancelled. Instead, communication between hemispheres enables the separation of motor activity for the two hands and helps to execute the required one-handed response.
精确控制上肢运动以响应外部刺激对于有效地与环境互动至关重要。众所周知，双手运动的准确执行依赖于大脑初级运动皮层（M1）之间精细协调的半球间通讯。然而，对于在准备好的双手运动突然取消期间半球间通讯的作用，我们知之甚少。本研究调查了在双手运动的完全和部分取消期间半球间相互作用的作用。在两项实验中，健康的年轻人类参与者在双手反应抑制任务期间接受了双侧 M1 的经颅磁刺激。在双手运动预期中，皮质运动兴奋性增加伴随着来自两个 M1 的抑制释放。在停止提示后，抑制重新作用于两个半球以成功取消完全的双手反应。然而，当停止提示信号指示部分取消（仅停止一个数字）时，抑制重新作用于取消的数字，但响应的数字表示被促进。在更困难的情况下，当非主导手（相对于主导手）仍在响应时，M1 之间的半球间通讯以 75 毫秒的延迟发生了这种分叉。我们的结果表明，一旦准备好双手反应，半球间通讯对于反应抑制是必不可少的。有趣的是，M1-M1 半球间电路似乎不是负责在部分取消期间观察到的所有运动成分的非选择性抑制的原因。相反，这种半球间通讯使双手反应成分解耦，并促进仅需要的单手运动的选择性启动。我们提供了第一个证据，证明半球间通讯在双手反应的突然运动取消期间起着重要作用。同时增加对两个半球的抑制有助于双手运动的取消。然而，该网络并不是负责观察到的两个手之一取消时观察到的广泛抑制运动活动的原因。相反，半球之间的通讯使双手的运动活动分离，并有助于执行所需的单手反应。
