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 re-engaged onto both hemispheres to successfully cancel the complete bimanual response. However, when the stop cue signalled partial cancellation (stopping of one digit only), inhibition was re-engaged 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 non-dominant, 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 non-selective 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.

中文翻译：

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半球间交流在完全和部分取消双手反应过程中的作用

响应外部刺激精确控制上肢运动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初级运动皮层 (M1s) 之间精心编排的半球间通信。然而，在准备好的双手运动突然取消期间，对半球间通信的作用知之甚少。目前的研究调查了半球间相互作用在双手运动完全和部分取消过程中的作用。在两个实验中，健康的年轻人类参与者在双手反应抑制任务期间接受了对两个 M1 的经颅磁刺激。预期双手运动的皮质运动兴奋性增加伴随着两个 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整的双手反应。然而，当停止提示发出部分取消信号（仅停止一位数字）时，对取消的数字重新进行抑制，但有助于响应数字表示。在更困难的条件下，当非优势手（而不是优势手）仍在响应时，M1 之间的半球间通信的这种分叉发生在 75 毫秒后。我们的结果表明，一旦准备好双手反应，半球间的交流对于反应抑制是不可或缺的。有趣的是，M1-M1 半球间电路似乎并不负责非选择性抑制在部分抵消期间观察到的所有运动分量。