Stretch Reflex Contributions to Multijoint Coordination

描述(申请人提供)：关节间协调异常是中风和脊髓损伤等神经病理的标志，有证据表明伸展反射功能的变化可能导致这种协调障碍。了解这些变化的意义，以及如何通过康复逆转或减少这些变化，最好是在未受损状态的情况下进行。然而，关于伸展反射在多关节运动和姿势的无损伤控制中的作用的信息很少。相反，大多数人类研究都集中在单个关节扰动的伸展反应上，这允许明确地调节肌肉长度，但没有解决实际扰动和涉及多个肌肉在多个自由度中作用的真实运动的复杂性。这项资助的目的是研究伸展反射对未受损伤的人类手臂多关节协调的贡献。具体地说，我们将确定响应整个肢体扰动而产生的肌肉激活模式是来自神经介导的肌肉间(异名)连接，还是仅仅代表通过骨骼连接的个别肌肉的自体(同名)反应。此外，这些动作的功能后果将通过量化任何观察到的反射动作的机械影响来解决。我们的目标是：1)通过对单个关节施加单个关节扰动来检查连接肘部和肩部的异名反射，并记录在两个关节处引起的肌肉活动的变化。这些结果将为异名联系提供一个“无模型”的评估。2)研究同名和异名牵拉反射通路在协调肢体整体干扰反应中的相对作用。这项研究将使用一个三自由度机器人来扰动肢体姿势，并使用一个3D生物力学模型来估计由此产生的肌肉长度变化。肌肉激活的变化与同名长度的变化没有直接联系，但很可能代表了异名通路的输出。3)探讨反射性肌肉活动变化对多关节力学调节的影响。前两个目标对于评估拉伸反射反应的存在和连通性很重要，但仅凭这两个目标并不能确定它们的功能后果。后者需要评估反射反应如何影响肢体的机械性能。这将使用非线性系统识别技术来估计伸展反射对多关节阻抗的贡献。这项研究将首次探讨多关节伸展反射在与正常功能相关的3自由度中协调手臂姿势的作用。我们的结果将为我们进一步研究卒中后异常反射功能提供必要的基础，并将阐明康复干预应在多大程度上针对脊髓机制。

DESCRIPTION (provided by applicant): Abnormal interjoint coordination is a hallmark of neuropathologies such as stroke and spinal cord injury, and there is evidence that changes in stretch reflex function may contribute to this discoordination. Understanding the significance of these changes and how they might be reversed or reduced through rehabilitation is best done in the context of the unimpaired state. However, there is little information regarding the role of stretch reflexes in the unimpaired control of multijoint movement and posture. Rather, most human studies have focused on the stretch response to single joint perturbations, which allow for unambiguous regulation of muscle length, but do not address the complexities of real perturbations and real movements involving multiple muscles acting in multiple degrees of freedom. This purpose of this grant is to examine stretch reflex contributions to multijoint coordination in the unimpaired human arm. Specifically we will determine if the muscle activation patterns generated in response to whole limb perturbations arise from neurally-mediated, intermuscular (heteronymous) connections or if they simply represent the autogenic (homonymous) responses of individual muscles linked via the skeleton. In addition, the functional consequences of these actions will be addressed by quantifying the mechanical impact of any observed reflex actions. Our Aims are: 1) To examine the heteronymous reflexes connecting the elbow and shoulder by applying single joint perturbations to a single joint, and recording the changes in muscle activity elicited at both joints. These results will provide a "model-free" assessment of heteronymous linkages. 2) To examine the relative contributions of homonymous and heteronymous stretch reflex pathways in coordinating the response to whole limb perturbations. This will be investigated using a 3DOF robot to perturb limb posture and a 3D biomechanical model to estimate the resulting muscle length changes. Changes in muscle activation that are not directly linked to homonymous length changes are likely to represent the output of heteronymous pathways. 3) To examine the influence of reflexively evoked changes in muscle activity on the regulation of multijoint mechanics. The first two Aims are important for assessing the existence and connectivity of stretch reflex responses, but alone do not establish their functional consequences. The latter requires an assessment of how reflex responses influence the mechanical properties of a limb. This will be accomplished using nonlinear system identification techniques to estimate stretch reflex contributions to multijoint impedance. This study will be the first to investigate the role of multijoint stretch reflexes for coordinating arm posture in the 3DOF relevant to normal function. Our results will provide the essential basis for our further investigations into abnormal reflex function following stroke and will elucidate the degree to which spinal mechanisms should be targeted by rehabilitation interventions.