The Forces Generated by Agonist Muscles during Isometric Contractions Arise from Motor Unit Synergies
The Forces Generated by Agonist Muscles during Isometric Contractions Arise from Motor Unit Synergies
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DOI：
10.1523/jneurosci.1265-22.2023
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发表时间：
2023-04-19
影响因子：
5.3
通讯作者：
Enoka, Roger M.
中科院分区：
文献类型：
--
作者：
Del Vecchio, Alessandro;Germer, Carina Marconi;Enoka, Roger M.
我们的研究的目的是确定低维的潜在成分，下文定义为运动单位模式，潜在的放电率的运动单位在两个膝伸肌（股内侧肌和外侧肌，8名男子）和两个手的肌肉（第一背侧骨间肌和鱼际，7名男子和1名女子）在次最大等长收缩。因子分析确定了两个独立的运动单位模式，捕获大部分的运动单位放电率的协方差。我们发现不同的分布的运动单位模式的手和vastii肌肉。平均而言，75%的大鱼际肌和第一背侧骨间肌的运动单位与它们所处的肌肉模块密切相关。相反，我们发现一个连续分布的运动单位模式跨越两个vastii肌肉模块。股内侧肌和股外侧肌的肌肉特异性运动单位模式的比例分别为60%和45%。其他运动单位要么与两个肌肉模块相关（共享输入），要么属于其他肌肉的模块（股外侧肌15%）。此外，一致性的运动单位池之间的放电率解释共享突触输入的存在。在模拟与480集成和消防神经元，我们证明了因子分析识别的运动单元模式具有高水平的准确性。我们的研究结果表明，相关的放电率的运动单位，包括运动单位的模式产生至少两个独立的来源，共同输入的运动神经元支配协同肌肉。
The purpose of our study was to identify the low-dimensional latent components, defined hereafter as motor unit modes, underlying the discharge rates of the motor units in two knee extensors (vastus medialis and lateralis, eight men) and two hand muscles (first dorsal interossei and thenars, seven men and one woman) during submaximal isometric contractions. Factor analysis identified two independent motor unit modes that captured most of the covariance of the motor unit discharge rates. We found divergent distributions of the motor unit modes for the hand and vastii muscles. On average, 75% of the motor units for the thenar muscles and first dorsal interosseus were strongly correlated with the module for the muscle in which they resided. In contrast, we found a continuous distribution of motor unit modes spanning the two vastii muscle modules. The proportion of the muscle-specific motor unit modes was 60% for vastus medialis and 45% for vastus lateralis. The other motor units were either correlated with both muscle modules (shared inputs) or belonged to the module for the other muscle (15% for vastus lateralis). Moreover, coherence of the discharge rates between motor unit pools was explained by the presence of shared synaptic inputs. In simulations with 480 integrate-and-fire neurons, we demonstrate that factor analysis identifies the motor unit modes with high levels of accuracy. Our results indicate that correlated discharge rates of motor units that comprise motor unit modes arise from at least two independent sources of common input among the motor neurons innervating synergistic muscles.