Firing behavior of single motor units of the tibialis anterior in human walking as non-invasively revealed by HDsEMG decomposition
Firing behavior of single motor units of the tibialis anterior in human walking as non-invasively revealed by HDsEMG decomposition
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DOI：
10.1088/1741-2552/aca71b
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发表时间：
2022-12-01
影响因子：
4
通讯作者：
Nakazawa，Kimitaka
中科院分区：
文献类型：
--
作者：
Yokoyama，Hikaru;Kaneko，Naotsugu;Nakazawa，Kimitaka
目的对运动单位 (MU) 的放电行为的研究提供了重要的神经肌肉控制信息，因为 MU 是神经肌肉系统的最小组织组成部分。人类婴儿腿部运动和啮齿动物运动期间激活的 MU 主要由脊髓中枢模式发生器 (CPG) 控制，表现出高度同步的放电。除了脊髓 CPG 之外，大脑皮层还参与成人行走过程中的神经肌肉控制。基于啮齿动物、人类婴儿和成人运动神经控制机制的差异，成人行走时的 MU 放电行为可能与其他人群有一些不同的特征。然而，到目前为止，由于技术问题，人类成人行走中 MU 的放电活动在很大程度上是未知的。方法最近的技术进步允许通过高密度表面肌电图 (HDsEMG) 分解对 MU 放电进行无创研究。我们通过 HDsEMG 分解研究了慢速行走期间胫骨前肌 (TA) 肌肉的 MU 放电行为。主要结果我们发现行走和稳定等长收缩之间 MU 的募集阈值调节。在行走过程中还观察到了双峰放电和步态阶段特定的放电。我们还发现在多种频率下行走时 MU 同步性很高，可能包括皮质和脊髓 CPG 相关成分。 MU 同步量在步态阶段和运动任务之间进行调节。这些结果表明，中枢神经系统在人类行走过程中灵活控制MU放电以产生适当的TA力量。意义本研究揭示了慢速行走时的MU行为，并证明了在动态运动任务中无创研究MU的可行性，这将为神经科学和生物医学工程领域的神经肌肉系统研究开辟新的前沿。
ObjectiveInvestigation of the firing behavior of motor units (MUs) provides essential neuromuscular control information because MUs are the smallest organizational component of the neuromuscular system. The MUs activated during human infants' leg movements and rodent locomotion, mainly controlled by the spinal central pattern generator (CPG), show highly synchronous firing. In addition to spinal CPGs, the cerebral cortex is involved in neuromuscular control during walking in human adults. Based on the difference in the neural control mechanisms of locomotion between rodent, human infants and adults, MU firing behavior during adult walking probably has some different features from the other populations. However, so far, the firing activity of MUs in human adult walking has been largely unknown due to technical issues.ApproachRecent technical advances allow noninvasive investigation of MU firing by high-density surface electromyogram (HDsEMG) decomposition. We investigated the MU firing behavior of the tibialis anterior (TA) muscle during walking at a slow speed by HDsEMG decomposition.Main resultsWe found recruitment threshold modulation of MU between walking and steady isometric contractions. Doublet firings, and gait phase-specific firings were also observed during walking. We also found high MU synchronization during walking over a wide range of frequencies, probably including cortical and spinal CPG-related components. The amount of MU synchronization was modulated between the gait phases and motor tasks. These results suggest that the central nervous system flexibly controls MU firing to generate appropriate force of TA during human walking.SignificanceThis study revealed the MU behavior during walking at a slow speed and demonstrated the feasibility of noninvasive investigation of MUs during dynamic locomotor tasks, which will open new frontiers for the study of neuromuscular systems in the fields of neuroscience and biomedical engineering.