Neural processes underlying human balance control

人体平衡控制的神经过程

• 批准号: RGPIN-2019-05851
• 负责人: Tokuno, Craig
• 金额: $ 2.04万
• 依托单位: Brock 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=738544
• 关键词: Neural; processes; underlying; human; balance

The ability to maintain balance is essential for the execution of many daily activities. When voluntarily initiating a movement or in anticipation of a predictable external perturbation to the body, individuals must rely on feedforward mechanisms to generate an anticipatory postural adjustment (APA) prior to movement onset. This involves a rapid change in corticospinal excitability to facilitate an early increase in postural muscle activity. This causes a shift in the body's center of mass so that destabilization from the upcoming movement is minimized. Since APAs act to stabilize the body, the timing and magnitude of APAs are dependent on the force and speed of the upcoming movement, whereby larger and earlier APAs are observed when larger or faster movements are expected. Interestingly however, older adults have a reduced ability to scale their anticipatory responses, such that they demonstrate more homogenous-sized APAs across varying levels of force. This deficit in APA scaling leads to greater postural instability prior to movement initiation and may explain why falls in daily life often occur as a result of an incorrect shifting of body weight during movement preparation. To better understand the neural mechanisms underlying the poor scaling and generation of APAs, the proposed research program will investigate how the central nervous system contributes to anticipatory balance control across the lifespan. A series of experiments will be conducted whereby young and older adults will self-initiate a movement (e.g., rising onto their toes) or respond to a predictable perturbation to the body. Variations in task difficulty and individual constraints will be introduced to examine the adaptability of the central nervous system and whether it is associated with the requirements of the task. At various times during the preparatory phase of these movements (i.e., prior to movement onset), the excitability of the spinal pathways will be assessed by electrically stimulating a peripheral nerve to elicit Hoffmann reflexes in the lower limb postural muscles while the involvement of the supraspinal areas will be determined by eliciting motor-evoked potentials using transcranial magnetic stimulation. Balance performance, in the form of APA magnitude and onset, will be quantified through body kinematic and kinetic recordings. The proposed research program will expand our fundamental understanding of the neural mechanisms underlying human anticipatory balance control and provide insight into how and why these processes become altered with advanced age. Knowledge developed from the program may also help to improve our ability to determine why falls and balance deficits arise due to aging.

保持平衡的能力对于许多日常活动的执行是必不可少的。当自愿开始一个运动或预期一个可预测的外部扰动对身体，个体必须依靠前馈机制产生一个预期的姿势调整（APA）在运动开始之前。这涉及皮质脊髓兴奋性的快速变化，以促进体位性肌肉活动的早期增加。这会导致身体重心的转移，从而将即将到来的运动带来的不稳定降到最低。由于APAs的作用是稳定身体，因此APAs的时间和大小取决于即将到来的运动的力量和速度，因此当预期更大或更快的运动时，观察到更大和更早的APAs。然而，有趣的是，老年人的预期反应能力较弱，因此他们在不同的力度下表现出更均匀的APAs。这种APA尺度的缺陷导致运动开始前更大的姿势不稳定，这可能解释了为什么在日常生活中，由于运动准备过程中体重的不正确转移而经常发生跌倒。为了更好地理解APAs的不良缩放和生成背后的神经机制，拟议的研究计划将研究中枢神经系统如何在整个生命周期中促进预期平衡控制。将进行一系列的实验，年轻人和老年人将自行发起一个运动（例如，用脚趾站立）或对可预测的身体扰动做出反应。任务难度和个体约束的变化将被引入，以检查中枢神经系统的适应性，以及它是否与任务的要求有关。在这些运动的准备阶段的不同时间（即，在运动开始之前），脊髓通路的兴奋性将通过电刺激周围神经来评估，以引起下肢姿势肌的霍夫曼反射，而椎上区域的参与将通过使用经颅磁刺激来引发运动诱发电位来确定。平衡表现，以APA大小和发作的形式，将通过身体运动学和动力学记录来量化。拟议的研究计划将扩大我们对人类预期平衡控制的神经机制的基本理解，并为这些过程如何以及为什么随着年龄的增长而改变提供见解。从该项目中获得的知识也可能有助于提高我们确定为什么跌倒和平衡能力不足会因年龄增长而出现的能力。