The Neural Control of Internal Joint State

描述(申请人提供)：大多数运动控制研究考虑中枢神经系统如何控制任务级变量，例如，研究中枢神经系统如何产生实现运动等行为所需的关节力矩。在这种情况下，肌肉产生的一组力矩决定了中枢神经系统对其激活。然而，这种对任务绩效的关注忽略了对另一组关键变量的控制，这些变量表征了内部关节结构的状态，如韧带和关节软骨(即韧带张力或骨接触力)。未能控制这些内部关节变量可能在短期内对健康产生重大后果(例如韧带断裂、关节脱位)，并在 长期(如慢性关节疼痛、关节炎)。因此，在确定肌肉激活时，中枢神经系统应该同时考虑任务表现和内部关节变量。然而，如何将内部关节变量纳入运动控制策略却知之甚少。这项建议中描述的实验的总体目标是评估这些问题，检查中枢神经系统对内部联合变量的控制。我们将使用动物模型来研究这些问题，重点是大鼠股四头肌对膝关节的控制。通过对大鼠膝关节的特殊解剖，可以清楚地区分股四头肌对任务表现变量(关节扭矩)和内部关节变量(内侧膝盖力)的影响。因此，使用这个模型，我们可以对内部关节变量的控制如何在一系列行为条件下的肌肉激活中反映出来做出强有力的预测。我们将进行三套相关的实验。在目标1中，我们将表征股四头肌的机械动作对任务绩效和内部关节变量的影响。我们假设股四头肌将产生类似的膝关节扭矩，但不同的内侧膝盖力。在目标2中，我们将检验股四头肌的神经控制是否反映了内部关节变量的调节。我们首先假设原封不动 动物，肌电信号变异性的相关性反映了膝关节内侧的平衡 力量。此外，我们假设，在选择性肌肉麻痹或膝盖力扰动之后，肌肉激活的长期适应将改善对内部关节变量的控制。在目标3中，我们将研究联合传入在控制内部联合变量中的作用。我们假设，关节传入不是用于肌肉激活的快速反馈控制，而是用于指导肌肉激活在对内部关节变量的扰动后的长期适应。这些实验在概念上简单易处理的实验模型中使用了一系列技术，对内部关节变量在行为神经控制中的作用进行了系统的分析。这些实验的结果有可能显著影响运动控制，无论是在我们对运动控制的基本理解中，还是在寻求恢复损伤后功能的临床应用中都是如此。

DESCRIPTION (provided by applicant): Most motor control studies consider how the CNS controls task level variables, examining, for example, how the CNS produces the joint torques necessary to achieve behaviors such as locomotion. In this context, it is the set of torques produced by a muscle that determines its activation by the CNS. However, this focus on task performance ignores the control of another critical set of variables, those characterizing the state of internal joint structures such as ligaments and articular cartilage (i.e. ligament strainsor bone contact forces). Failure to regulate these internal joint variables can have significant consequences to health both in the short term (e.g. ligament rupture, joint dislocation) and in the long term (e.g. chronic joint pain, arthritis). The CNS should therefore consider both task performance and internal joint variables when determining muscle activations. How internal joint variables might be incorporated into motor control strategies, however, is poorly understood. The overall goal of the experiments described in this proposal is to evaluate these issues, examining the control of internal joint variables by the CNS. We will examine these issues using an animal model, focusing on the control of the knee joint by quadriceps muscles in the rat. The specific anatomy of the rat knee allows for a clear separation between the effects of quadriceps muscles on task performance variables (joint torques) and internal joint variables (mediolateral patellar forces). Using this model we can therefore make strong predictions about how the control of internal joint variables should be reflected in muscle activations across a range of behavioral conditions. We will perform three sets of related experiments. In Aim 1 we will characterize the mechanical actions of quadriceps muscles on task performance and internal joint variables. We hypothesize that quadriceps muscles will produce similar knee joint torques but distinct mediolateral patellar forces. In Aim 2, we will examine whether the neural control of quadriceps reflects the regulation of internal joint variables. We first hypothesize that in intact animals, the correlation in the variability of EMGs reflects the balancing of mediolateral patellar forces. Further, we hypothesize that following selective muscle paralysis or perturbations of patellar forces, long term adaptations in muscle activations will improve the control of internal joint variables. In Aim 3 we will examine the role of joint afferents in the control of internal jont variables. We hypothesize that joint afferents are not used for rapid feedback control of muscle activations but are used to guide long term adaptations of muscle activations following perturbations to internal joint variables. These experiments provide a systematic analysis of the role of internal joint variables in the neural control of behavior, using a range of techniques in conceptually simple and tractable experimental model. The results of these experiments have the potential to significantly impact motor control, both in our basic understanding of motor control and in clinical applications that seek to restore function after injury.