Startling stimuli increase maximal motor unit discharge rate and rate of force development in humans.
Startling stimuli increase maximal motor unit discharge rate and rate of force development in humans.
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DOI：
10.1152/jn.00115.2022
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发表时间：
2022-09-01
影响因子：
2.5
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中科院分区：
文献类型：
--
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成人的最大力量发展速率是由最大运动单元放电速率决定的，然而，潜在的突触输入的起源尚不清楚。在这里，我们测试了一个假设，即最大运动单位放电率会随着一个惊人的提示而增加，一个刺激据称会激活桥脑髓网状形成神经元，通过快速传导轴突与运动神经元建立单突触和双突触连接。22名男性被要求在休息时“尽可能快、尽可能硬”地产生等距膝关节伸肌力，达到最大自主力的75%，以响应视觉（VC）、视觉-听觉（VAC; 80 dB）或视觉-惊吓提示（VSC; 110 dB）。通过分解股外侧肌和内侧肌的高密度表面肌电图记录来估计运动神经元的活动。与VAC和VC相比，VSC的反应时间显著缩短。VSC进一步引发了更快的神经力学反应，包括每运动单位每秒更多的放电次数和更大的最大力发展速度，在VAC和VC之间没有差异。我们首次提供了证据，表明对运动神经元的突触输入会随着令人吃惊的提示而增加，这表明皮层下通路对人类最大运动神经元输出的贡献。新的和值得注意的运动单元放电特性是人类力发展速度的关键决定因素，但支撑这种输出的神经基质仍然未知。通过高密度肌电图的分解，我们发现在惊人的听觉刺激后，每运动单位每秒的放电次数和力的发展速度都更快。这些观察结果表明，皮层下可能对成年人体内最大运动单位放电率有贡献。
Maximal rate of force development in adult humans is determined by the maximal motor unit discharge rate, however, the origin of the underlying synaptic inputs remains unclear. Here, we tested a hypothesis that the maximal motor unit discharge rate will increase in response to a startling cue, a stimulus that purportedly activates the pontomedullary reticular formation neurons that make mono- and disynaptic connections to motoneurons via fast-conducting axons. Twenty-two men were required to produce isometric knee extensor forces “as fast and as hard” as possible from rest to 75% of maximal voluntary force, in response to visual (VC), visual-auditory (VAC; 80 dB), or visual-startling cue (VSC; 110 dB). Motoneuron activity was estimated via decomposition of high-density surface electromyogram recordings over the vastus lateralis and medialis muscles. Reaction time was significantly shorter in response to VSC compared with VAC and VC. The VSC further elicited faster neuromechanical responses including a greater number of discharges per motor unit per second and greater maximal rate of force development, with no differences between VAC and VC. We provide evidence, for the first time, that the synaptic input to motoneurons increases in response to a startling cue, suggesting a contribution of subcortical pathways to maximal motoneuron output in humans. NEW & NOTEWORTHY Motor unit discharge characteristics are a key determinant of rate of force development in humans, but the neural substrate(s) underpinning such output remains unknown. Using decomposition of high-density electromyogram, we show greater number of discharges per motor unit per second and greater rate of force development after a startling auditory stimulus. These observations suggest a possible subcortical contribution to maximal in vivo motor unit discharge rate in adult humans.
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影响因子：
2
作者：
Buford, JA;Davidson, AG
通讯作者：
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