The interaction between cortex and muscles under hand motor with different force states has not been quantitatively investigated yet, which to some extent places the optimized movement tasks design for brain-computer interface (BCI) applications in hand motor rehabilitation under uncertainty. Converging evidence has suggested that both the descending corticospinal pathway and ascending sensory feedback pathway are involved in the generation of corticomuscular coupling. The present study aimed to explore the corticomuscular coupling during hand motor task with enhancing force and steady-state force. Twenty healthy subjects performed precision grip with enhancing and static force using the right hand with visual feedback of exerted force. Mutual information and Granger causal connectivity were assessed between electroencephalography (EEG) over primary motor cortex and electromyography (EMG) recordings, and statistically analyzed. The results showed that the mutual information value was significantly larger for static force in the beta and alpha frequency band than enhancing force state. Furthermore, compared with enhancing force, the Granger causal connectivity of descending pathways from cortex to muscle was significantly larger for static force in the beta and high alpha frequency band (10-20 Hz), indicating the connection between the primary motor cortex and muscle was strengthened for static force. In summary, the hand grip with static force resulted in an increasing corticomuscular coupling from EEG over the primary motor cortex to EMG compared with enhancing force, implying more attention was required in the static force state. These results have important implications toward motor rehabilitation therapy design for the recovery of impaired hand motor functions.

中文翻译：

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与增强力相比，静力握持过程中增强的降皮质肌肉耦合

手部运动在不同力状态下的皮层和肌肉之间的相互作用尚未得到定量研究，这在一定程度上将手部运动康复中脑机接口（BCI）应用的优化运动任务设计置于不确定性之下。综合证据表明，下行皮质脊髓通路和上行感觉反馈通路都参与了皮质肌肉耦合的产生。本研究旨在通过增强力和稳态力探索手部运动任务中的皮质肌肉耦合。20 名健康受试者使用右手和施加力的视觉反馈以增强力和静态力进行精确抓握。在初级运动皮层的脑电图 (EEG) 和肌电图 (EMG) 记录之间评估互信息和格兰杰因果连接，并进行统计分析。结果表明，β和α频段静力的互信息值显着大于增强力状态。此外，与增强力相比，β和高α频段（10-20Hz）静力从皮层到肌肉的下行通路的格兰杰因果连接显着更大，表明初级运动皮层和肌肉之间的联系是加强静力。总之，与增强力相比，静力握力导致从脑电图通过初级运动皮层到肌电图的皮质肌肉耦合增加，这意味着在静态力状态下需要更多的关注。这些结果对用于恢复受损手部运动功能的运动康复疗法设计具有重要意义。