Stretch Reflex Contributions to Multijoint Coordination

描述（由申请人提供）：我们对长潜伏期牵张反射（LLSRs）如何有助于控制人类手臂的多关节姿势和运动的理解存在根本性的差距。这是一个重要的问题，因为许多神经系统疾病都会损害牵张反射，导致运动功能障碍。然而，通过改变反射行为来增强运动功能的尝试在很大程度上是模棱两可的，这至少部分是由于特定反射亚型和运动能力之间的未知关系。我们的中心主题是，大部分的差距可以通过考虑的途径，有助于LLSR和他们的具体的，依赖于上下文的运动功能的贡献填补。LLSR包含至少两个关键的行为成分：“稳定反射”，有助于姿势调节，以及“触发反应”，用于快速释放计划的行动。我们已经证明，这些行为是由不同的途径介导的，它们的相对重要性取决于所执行的任务。我们最近的工作集中在LLSR的稳定成分上。在这里，我们建议调查触发反应。我们的中心假设是，触发反应可以独立于稳定反射，根据我们的初步数据表明，稳定LLSR中风后丢失，但触发反应幸免。重要的是，我们的数据还表明，适当触发的反应可以提高中风患者的速度和协调性，这可能是有效康复的基础。然而，首先，我们必须澄清LLSR在控制未受损的姿势和运动中的作用，以及它在中风后的完整性和功能。我们的具体目标是：1）确定稳定反射和触发反应是否是独立控制的; 2）确定不确定性如何影响触发反应的计划、执行和功效;以及3）确定由于中风损害的脑损伤如何影响稳定牵张反射和触发反应。前两个目标侧重于触发反应的行为相关性，并将在未受损的受试者中完成，使用3D机器人操纵器在从保持手臂姿势到启动伸展的关键过渡期间对LLSR进行表征。我们的第三个目标将在中风受试者和年龄匹配的对照组中完成。它与前两个目标平行，但也将使用弥散张量成像（DTI）来量化下行通路中的病变，这些病变被认为是调节LLSR的稳定和触发成分的。这项研究的贡献将是清楚地描述触发反应在运动控制中的作用，该作用如何与LLSR的姿势稳定成分相结合，以及LLSR如何在中风后与促成它的神经通路相关受损。我们希望为在康复训练范例中使用触发反应奠定基础，目的是提高在适当的时间自愿启动适当运动模式的能力。中风幸存者吃了乳酸脱氢酶

DESCRIPTION (provided by applicant): There is a fundamental gap in our understanding of how long-latency stretch reflexes (LLSRs) contribute to the control of multijoint posture and movement in the human arm. This is an important problem because many neurological disorders impair stretch reflexes, resulting in well-documented motor dysfunction. Attempts to enhance motor function through a modification of reflex behavior have been largely equivocal, however, due at least in part to the unknown relationships between specific reflex subtypes and motor abilities. Our central theme is that much of the gap can be filled by considering the pathways that contribute to LLSRs and their specific, context-dependent contributions to motor function. LLSRs contain at least two key behavioral compo- nents: "stabilizing reflexes", contributing to posture regulation, and "triggered reactions" for the rapid release of planned actions. We have shown that these behaviors are mediated by separate pathways and that their relative importance depends on the task performed. Our recent work focused on the stabilizing component of the LLSR. Here we propose to investigate triggered reactions. Our central hypothesis is that triggered reactions can act independently from stabilizing reflexes, based on our preliminary data demonstrating that stabilizing LLSRs are lost following stroke but that triggered reactions are spared. Importantly, our data also suggest that appropriately triggered reactions increase speed and coordination in stroke subjects, potentially forming the basis for effective rehabilitation. First, however, we must clarify the LLSR role in controlling unimpaired posture and movement, and its integrity and function following stroke. Our Specific Aims are: 1) to determine if stabilizing reflexes and triggered reactions are controlled independently; 2) to determine how uncertainty affects the planning, execution and efficacy of triggered reactions; and 3) to determine how brain injury due to stroke im- pairs stabilizing stretch reflexes and triggered reactions. The first two aims focus on the behavioral relevance of triggered reactions, and will be completed in unimpaired subjects using a 3D robotic manipulator to charac- terize LLSRs during the key transition from maintaining arm posture to initiating a reach. Our third aim will be completed in stroke subjects and age-matched controls. It parallels the first two aims, but also will use diffusion tensor imaging (DTI) to quantify lesions in the descending pathways thought to regulate the stabilizing and triggered components of the LLSR. The contributions of this research will be a clear description of the role of triggered reactions in the control of movement, how that role is integrated with posture-stabilizing components of the LLSR, and how the LLSR is impaired following stroke in relation to the neural pathways contributing to it. With this refined understanding, we hope to lay the groundwork for using triggered reactions in rehabilitation training paradigms aimed at enhancing the ability to voluntarily initiate appropriate motor patterns at appropri- ate latencies in stroke survivors.