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）：运动神经元动作电位的相关放电是由分支神经元或脊髓上源的节律驱动传递的共同突触输入引起的。对运动单位活动的影响被量化为运动单位同步。尽管在技术上具有挑战性，但运动单位同步的测量是一项强大的技术，可以提供有关随意肌肉收缩期间人类中枢神经系统连接的信息。可以通过对运动单元对的放电时间的时域和频域分析来区分这两个公共输入源。该提案重点关注一个新兴概念，即运动单元同步是感觉运动皮层中常见节律活动的结果。运动神经元的下行驱动中这种节律性的存在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。目标 1 是一项建模研究，它将我们现有的运动单位模型扩展为包括与多室树突树耦合的神经元膜电位的基于电流的阈交叉模型。通过该模型，我们将通过计算机模拟明确控制运动神经元的突触输入，从而确定常见分支和节律性突触输入对运动单元相关放电的影响。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，低力时运动单元同步量较少。运动单元对的相关放电将以多种放电速率进行测量，以区分三个可能的因素：共同突触输入比例随兴奋性驱动水平的变化、高阈值运动单元的更大同步性以及源的变化共同的突触输入。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震颤的影响。我们期望发现运动单位同步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水平和肌肉收缩类型的变化而变化，这影响了运动神经元突触输入的稳定性。表现。该项目的成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。