Motor Unit Synchronization and Muscle Function

运动单位同步和肌肉功能

• 批准号: 6640248
• 负责人: ROGER M. ENOKA
• 金额: $ 27.77万
• 依托单位: UNIVERSITY OF COLORADO
• 依托单位国家: 美国
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-07-01 至 2005-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6640248
• 关键词: action potentials; bioperiodicity; clinical research; computer simulation; electrodes; electromyography; electrophysiology; human subject; membrane potentials; motor neurons; muscle contraction; muscle function; neural transmission; synapses; tremor

DESCRIPTION (provided by applicant): The correlated discharge of action potentials by motor neurons is caused by common synaptic input that is delivered either by branched neurons or by rhythmic drive from supraspinal sources. The effect on motor unit activity is quantified as motor unit synchronization. Although technically challenging, the measurement of motor unit synchronization is a powerful technique that provides information about connections in the human CNS during voluntary muscle contractions. The two sources of common input can be distinguished by time-and frequency-domain analyses of the discharge times of pairs of motor units. This proposal focuses on the emerging concept that motor unit synchronization is a consequence of common rhythmic activity in the sensorimotor cortex. The presence of this rhythmicity in the descending drive onto motor neurons may enhance physiological tremor. We hypothesize that motor unit synchronization is caused by common oscillations present in the synaptic input received by motor neurons and that these increase with excitatory drive and impair the ability to perform steady contractions. Aim 1 is a modeling study that extends our existing motor unit model to include a current-based, threshold-crossing model of neuronal membrane potential coupled to a multi-compartment dendritic tree. With this model, we will explicitly control the synaptic inputs to the motor neurons with computer simulations and thereby determine the effects of common branched and rhythmic synaptic input on the correlated discharges of motor units. Interpretation of the experimental results (Aims 2 and 3) will be based on the outcomes of the simulations. Aim 2 will determine why the amount of motor unit synchronization is less at low forces compared with high forces. The correlated discharge of pairs of motor units will be measured at several discharge rates to distinguish among three possible factors: variation in the proportion of common synaptic input with the level of excitatory drive, greater synchronization for high threshold motor units, and changes in the source of common synaptic input. Aim 3 will examine the effect of motor unit synchronization on physiological tremor by comparing changes in the time- and frequency-domain measures of motor unit synchronization with the steadiness of performance across different types of muscle contractions. We expect to find that motor unit synchronization is largely due to common oscillations in the synaptic input onto motor neurons, that the proportion of common input changes both with the level of excitatory drive and the type of muscle contraction, and that this influences the steadiness of performance. The outcomes of this project will have direct application to the measurement and interpretation of motor unit synchronization in neurological patients.

描述（由申请人提供）：运动神经元的动作电位的相关放电是由共同的突触输入引起的，该突触输入由分支神经元或由来自脊髓上来源的节律驱动递送。对运动单位活动的影响被量化为运动单位同步。虽然在技术上具有挑战性，但运动单位同步的测量是一种强大的技术，可以提供有关人体中枢神经系统在随意肌肉收缩期间的连接信息。这两个来源的共同输入可以区分的时间和频域分析的放电时间对电机单位。这项建议的重点是新兴的概念，运动单位同步是一个共同的节奏活动的结果，在感觉运动皮层。在运动神经元的下行驱动中存在这种节律性可能会增强生理性震颤。我们假设运动单位同步是由运动神经元接收的突触输入中存在的常见振荡引起的，并且这些振荡随着兴奋性驱动而增加，并损害执行稳定收缩的能力。目的1是一个建模研究，扩展了我们现有的运动单元模型，包括一个基于电流的，阈值交叉模型的神经元膜电位耦合到一个多室树突树。利用这个模型，我们将明确地控制突触输入的运动神经元的计算机模拟，从而确定共同的分支和节奏的突触输入的运动单位的相关放电的影响。实验结果（目标2和3）的解释将基于模拟结果。目标2将确定为什么与高力相比，低力下的运动单元同步量较少。运动单位对的相关放电将在几个放电率进行测量，以区分三个可能的因素：共同突触输入的比例与兴奋性驱动水平的变化，高阈值运动单位的更大同步，以及共同突触输入源的变化。目标3将通过比较运动单位同步的时域和频域测量的变化与不同类型肌肉收缩的性能稳定性来检查运动单位同步对生理性震颤的影响。我们期望发现运动单位的同步化在很大程度上是由于运动神经元突触输入的共同振荡，共同输入的比例随着兴奋性驱动的水平和肌肉收缩的类型而变化，这影响了表现的稳定性。该项目的结果将直接应用于神经系统患者运动单位同步的测量和解释。