Sex- and Task-dependent Modulation of Spinal and Cortical Motor Neuron Excitability During Fatigue

疲劳期间脊髓和皮质运动神经元兴奋性的性别和任务依赖性调节

• 批准号: RGPIN-2020-04157
• 负责人: Kalmar, Jayne
• 金额: $ 2.91万
• 依托单位: Wilfrid Laurier University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=739710
• 关键词: Sex; Task; dependent; Modulation; Spinal

Muscle activation during fatiguing activity is modulated by supraspinal, spinal, and peripheral factors that contribute to or compensate for failure at multiple points along the pathway from brain to muscle. Two potential compensatory mechanisms include, i) increased gain of cortical motor neurons or "intracortical facilitation" (ICF), and ii) increased gain of spinal motor neurons via "persistent inward current" (PIC). It is unclear how these two compensatory mechanisms function together to maintain motor output and reduce sense of effort during fatigue. Earlier work suggests that cortical gain increases to offset failure as fatiguing activity continues. It is possible spinal motor neuron gain increases to offset fatigue, and that fatigue-resistance observed in females compared to males, may be due a compensatory increase in PIC. Caffeine is a central nervous system stimulant that can be used to assess central contributions to neuromuscular fatigue and could be used to assess the relationship between PIC and fatigue. However, very little is known about caffeine-induced changes in neuromuscular function and fatigue in females, and it is unclear how such effects might change across the menstrual cycle. These questions must be answered before caffeine can be used to investigate sex-dependent relationships between spinal motor neuron gain and subjective sense of fatigue. Finally, fatigue-induced changes in the gain of spinal motor neurons that control locomotion may be modulated by changing sensory information from the sole of the foot. To date, the role of plantar cutaneous afferents in the modulation of PIC is unknown. Work in this area advances slowly because estimates of motor neuron PIC in humans rely on invasive intramuscular recording methods that yield a small sample of data. New technologies are now emerging that extract a large sample of data via "decomposition" of a noninvasive surface recording. Although, this high-yield technology has the potential to be a game-changer in human neurophysiological research, work is required to validate the approach. The proposed program of research aims to, 1) demonstrate the role that cortical and spinal motor neuron gain play in offsetting fatigue in males and females, 2) investigate the relationship between fatigue-associated changes in PIC and force sensation using caffeine after establishing effects of caffeine on neuromuscular function across the menstrual cycle, and 3) explore the role of regionalized cutaneous afferent input that may contribute to the modulation of spinal MN PIC during functional movement using both conventional intramuscular recordings as well as high-yield decomposition.

疲劳活动期间的肌肉激活受到脊柱上、脊柱和外周因素的调节，这些因素有助于或补偿从大脑到肌肉的路径上多个点的衰竭。两种潜在的补偿机制包括，i）增加皮质运动神经元的增益或“皮质内促进”（ICF），以及 ii）通过“持续内向电流”（PIC）增加脊髓运动神经元的增益。目前尚不清楚这两种补偿机制如何共同发挥作用以维持运动输出并减少疲劳期间的努力感。早期的研究表明，随着疲劳活动的持续，皮质增益会增加以抵消失败。脊髓运动神经元增益的增加可能会抵消疲劳，并且与男性相比，女性观察到的抗疲劳性可能是由于 PIC 的补偿性增加所致。咖啡因是一种中枢神经系统兴奋剂，可用于评估中枢神经肌肉疲劳的贡献，并可用于评估 PIC 与疲劳之间的关系。然而，人们对咖啡因引起的女性神经肌肉功能和疲劳的变化知之甚少，也不清楚这种影响在整个月经周期中如何变化。在使用咖啡因研究脊髓运动神经元增益和主观疲劳感之间的性别依赖性关系之前，必须回答这些问题。最后，疲劳引起的控制运动的脊髓运动神经元增益的变化可以通过改变脚底的感觉信息来调节。迄今为止，足底皮肤传入神经在 PIC 调节中的作用尚不清楚。该领域的工作进展缓慢，因为对人类运动神经元 PIC 的估计依赖于产生小样本数据的侵入性肌内记录方法。现在正在出现的新技术可以通过“分解”非侵入性表面记录来提取大量数据样本。尽管这种高产技术有可能成为人类神经生理学研究的游戏规则改变者，但仍需要开展工作来验证该方法。拟议的研究计划旨在：1）证明皮质和脊髓运动神经元增益在抵消男性和女性疲劳方面的作用，2）在确定咖啡因对整个月经周期神经肌肉功能的影响后，使用咖啡因研究疲劳相关的 PIC 变化和力感觉之间的关系，以及 3）探索区域化皮肤传入输入的作用，这可能有助于 使用传统的肌内记录和高产分解在功能性运动过程中调节脊髓 MN PIC。