Neuromechanical modeling of postural responses

描述(由申请人提供)：长期目标是了解姿势和运动的神经肌肉骨骼动力学。尽管有能力量化和模拟运动行为，但目前人们对神经系统如何协调复杂的肌肉激活模式以在自然行为中产生运动功能知之甚少。如果没有这个基本的了解，人们就无法预测肌肉模式紊乱对神经受损个体运动功能的影响。这项建议探索了一个令人兴奋的新概念，即复杂的肌肉激活模式可以分解为几个功能肌肉组，称为肌肉协同效应。这种简单的功能分割对于神经假体的设计、恢复运动控制的治疗干预以及理解神经元运动机制的结构和功能都有重要的意义。这项建议的目的是确定在正常和神经受损动物的姿势反应中，猫后肢的肌肉协同作用及其生物力学功能。PI假设有限数量的肌肉协同作用可以产生在姿势反应中观察到的复杂的肌肉激活模式，并且每个肌肉协同作用产生特定的、与任务相关的机械功能。新的方法是将详细的实验数据分析与计算机模拟相结合，以了解肌肉协同作用如何为神经系统提供产生自然运动行为的“积木”。CAT是这些研究的理想模型，因为(1)它允许检查同一动物在各种姿势任务中的肌肉协同作用，包括神经损伤前和神经损伤后，以及(2)它允许通过活体肌肉刺激实验直接测试模型的有效性。这一结果将为理解神经系统如何在肌肉激活水平上实现对任务级变量的控制建立一个新的理论框架。这一提议的主要创新之一是一种新的协同识别方法，允许将复杂的对象分解为有意义的部分。使用这个新的框架，PI将评估肌肉协同作用如何随着特定的神经损伤而变化，以及由此对运动功能的影响。在目标1中，他们将在平衡猫、完整和神经受损的猫(脊髓横断或大纤维周围神经病)中确定肌肉协同效应，并确定它们与地面反作用力的关系。在目标2中，PI将实现并使用猫后肢的3-D肌肉骨骼模型来定义肌肉协同组织的静态生物力学约束，以产生地面反作用力。这项工作为复杂肌肉模式的功能解释奠定了理论基础，这些模式是自然运动行为的基础。它提供了肌肉协调和功能之间的关键联系，将推动开发实用的解决方案，以恢复神经受损个体的运动功能，如神经修复、神经假体和神经康复。

DESCRIPTION (provided by applicant): The long-term goal is to understand neuromusculoskeletal dynamics of posture and locomotion. Despite the ability to quantify and simulate motor behaviors, one currently has little understanding of how the nervous system coordinates complex muscle activation patterns to produce motor functions during natural behaviors. Without this basic understanding, one cannot predict the impact of disordered muscle patterns on motor function in neurologically impaired individuals. This proposal explores the exciting new concept that complex muscle activation patterns can be decomposed into a few functional muscle groupings, termed muscle synergies. This simple and functional partitioning has important implications for the design of neural prostheses, therapeutic interventions to restore motor control, and for understanding the structure and function of neuronal mechanisms for movement. The objective of this proposal is to identify muscle synergies and their biomechanical functions in the cat hindlimb during postural responses in normal and neurologically impaired animals. The PIs hypothesize that a limited number of muscle synergies can produce the complex muscle activation patterns observed during postural responses, and that each muscle synergy produces a specific, task-related mechanical function. The novel approach is to integrate the analysis of detailed experimental data with computer simulations to understand how muscle synergies provide the nervous system with 'building blocks' for generating natural motor behaviors. The cat is an ideal model for these studies because (1) it allows examining muscle synergies in the same animal in a variety postural tasks, both pre- and post-neurological impairment, and (2) it allows to directly test the validity of the model with in vivo muscle stimulation experiments. The results will establish a new theoretical framework for understanding how the nervous system implements control of task-level variables at he level of muscle activations. One of the major innovations of this proposal is a novel method of synergy identification that allows for breaking complex objects into meaningful parts. Using this new framework the PIs will evaluate how muscle synergies change with specific neurological impairments and the resulting effect on motor function. In Aim 1 they will identify muscle synergies during balance cats, in intact and neurologically impaired cats (spinal cord transection or large fiber peripheral neuropathy), and determine their relationship to ground reaction forces. In Aim 2 the PIs will implement and use a 3-D musculoskeletal model of the cat hindlimb to define static biomechanical constraints on muscle synergy organization for ground reaction force production. This work forms a theoretical basis for the functional interpretation of complex muscle patterns that underlie natural motor behavior. It provides a critical link between muscle coordination and function that will drive the development of practical solutions to restore motor function in neurologically impaired individuals such as neural repair, neural prosthetics, and neural rehabilitation.