Neuromechanical Modeling of Postural Responses

描述（由申请人提供）：由于失去平衡而跌倒是老年人受伤和死亡的主要原因，也是广泛的神经、肌肉骨骼和认知缺陷的衰弱症状。然而，由于许多神经和肌肉骨骼因素可能导致平衡障碍，或者相当于代偿策略，因此临床医生通常很难评估平衡障碍的严重程度，或确定其潜在原因。该项目的目的是了解在站立平衡控制过程中，前馈和反馈神经机械元件对姿势稳定性的调节原理。我们选择在一次数据收集的时间框架内，研究可以被神经系统快速调节或选择的神经力学元素。我们将前馈神经机械元件定义为那些在预期体位扰动（如体位结构和体位肌张力）时调节肌肉骨骼系统内在机械稳定性的元件。我们将反馈神经机械元素定义为那些在姿势扰动后反应性激活肌肉的元素，包括任务级反馈增益、肌肉协同作用和脊柱反射。我们假设前馈和反馈神经机械元件被调制以实现隐含的性能目标，如稳定性、可操作性、能量最小化或对不确定性的鲁棒性。不同的表现目标可以解释不同试验、不同个体、不同环境或不同运动缺陷中观察到的运动变化。我们预测，神经机械元素的各种组合可能产生质量相似的运动，但数量上不同的功能和能量后果。在Aim 1中，我们将研究前馈和反馈神经机械元件在正常猫和神经受损猫站立平衡控制中的相互作用；在短期和长期的姿势适应完整的动物在Aim 3。在目标2中，我们将使用姿势控制的神经力学模型来确定功能和能量成本之间的权衡，以及可能在健康和疾病中驱动姿势适应的约束。这一建议继续我们发展一个通用的科学框架，以实现我们的长期目标，即理解、诊断和预测平衡缺陷和一般运动障碍患者的最佳运动功能。

DESCRIPTION (provided by applicant): Falls due to a loss of balance are a primary cause of injury and death in the elderly, and a debilitating symptom of a wide range of neurological, musculoskeletal, and cognitive deficits. However, because many neural and musculoskeletal elements can contribute to balance impairments - or equivalently to compensatory strategies - it is often difficult for clinicians to evaluate the severity of balance impairments, or to identify their underlying causes. The objective of this project is to understand the principles governing the modulation of feedforward and feedback neuromechanical elements contributing to postural stability during standing balance control. We have chosen to study the neuromechanical elements that can be rapidly modulated or selected by the nervous system, within the time frame of one session of data collection. We define feedforward neuromechanical elements to be those that adjust the intrinsic mechanical stability of the musculoskeletal system in anticipation of a postural perturbation, such as postural configuration and postural muscle tone. We define feedback neuromechanical elements to be those that activate muscles reactively following postural perturbations, and include task-level feedback gains, muscle synergies, and spinal reflexes. We hypothesize that the feedforward and feedback neuromechanical elements are modulated to achieve implicit performance goals such as stability, maneuverability, energy minimization, or robustness to uncertainty. Differing performance goals could explain variations in movement observed across trials, across individuals, across contexts, or across motor deficits. We predict that various combinations of neuromechanical elements may produce qualitatively similar movements, and yet quantitatively different functional and energetic consequences. We will study interactions between feedforward and feedback neuromechanical elements for standing balance control in normal and neurologically-impaired cats in Aim 1; during short- and long- term postural adaptations in intact animals in Aim 3. In Aim 2, we will identify tradeoffs between functional and energetic costs and constraints that may drive postural adaptations in both health and disease using neuromechanical models of postural control. This proposal continues our development of a general scientific framework toward our long-term goal of understanding, diagnosing, and predicting optimal motor function in individuals with balance deficits, and motor impairments in general. PUBLIC HEALTH RELEVANCE: Falls due to a loss of balance are the leading cause of injury leading to death in older adults. Loss of balance causing someone to fall can happen due to a number of neurological and musculoskeletal deficits. We will identify how specific neurological impairments alter subtle, but measurable changes in balance control. We also develop computer simulation and analysis tools that may eventually help physicians predict how best to treat balance impairments.