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: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=757853
• 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.

疲劳活动时的肌肉激活是由椎骨上、脊柱和外周因素调节的，这些因素导致或补偿了从大脑到肌肉通路上多个点的失败。两种潜在的代偿机制包括：1)皮质运动神经元或“皮质内促进”（ICF）增加增益；2)通过“持续内向电流”（PIC）增加脊髓运动神经元增益。目前尚不清楚这两种代偿机制如何共同发挥作用，以维持运动输出并减少疲劳时的努力感。早期的研究表明，随着疲劳活动的持续，皮层的增加抵消了失败。脊髓运动神经元的增加可能是为了抵消疲劳，与男性相比，在女性中观察到的疲劳抵抗可能是由于PIC的代偿性增加。咖啡因是一种中枢神经系统兴奋剂，可用于评估中枢对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月经周期中是如何变化的。在咖啡因被用于研究脊髓运动神经元增益和主观疲劳感之间的性别依赖关系之前，这些问题必须得到回答。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能通过改变来自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。这一领域的工作进展缓慢，因为对人类运动神经元PIC的估计依赖于侵入性肌肉内记录方法，产生的数据样本很少。新技术正在兴起，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改变人类神经生理学研究的游戏规则，但还需要进一步的工作来验证这种方法。本研究计划旨在：1)证明皮质和脊髓运动神经元增益在男性和女性中抵消疲劳的作用；2)在确定咖啡因对月经周期神经肌肉功能的影响后，研究疲劳相关的PIC变化与使用咖啡因的力感觉之间的关系。3)利用传统的肌内记录和高产分解，探索区域性皮肤传入输入在功能运动期间可能有助于脊柱MN PIC调节的作用。