Adaptive mechanisms in the control of interlimb coordination during locomotion

肢体间协调对于在不断变化的环境中航行时的动态稳定性和改变运动速度至关重要，涉及到中枢神经系统不同水平上的复杂动态相互作用和肌肉骨骼系统的紧急特性。尽管肢体间协调的动态控制很重要，但在陆生哺乳动物中却没有明确的定义。我的研究计划的长期目标是阐明在运动过程中控制肢体间协调的神经生理学和生物力学机制。为了实现这一目标，猫被训练踩在有四个独立表面的跑步机上，这样前肢和后肢或左右两侧的速度都可以独立控制。皮带可以以相同的速度运行(捆绑皮带运动)，也可以以不同的速度运行(分体皮带运动)。因此，可以系统地操纵肢体之间的速度或速度差异，以挑战肢体之间的协调，揭示适应机制。慢性植入被用来记录肌肉活动和唤起反射，而三维运动捕捉则获得详细的运动运动学。在完整猫和横断脊椎的猫中进行比较，以确定脊柱机制在协调肢体方面的贡献。第一个目标是描述绑带和分带运动中的反射调制。反应能力对于快速适应外部干扰是必不可少的。我们假设，反射幅度1)将随TASK进行调制，2)在分带运动的基础上逐步变化较小。我们还假设，在完整猫和脊髓猫身上的结果将是相似的，这表明反射调制主要是在脊髓水平上决定的。第二个目标是描述绑带和分带运动中肌肉活动的模式。我们假设1)肌肉协同作用利用一些肌肉的双功能性质，2)协同作用可以延伸到不止一个肢体，3)它们主要在脊柱水平上被控制。第三个目标是描述捆绑带和劈裂带运动时肢体内部和肢体之间的动态协调。我们假设，当适应速度和施加在肢体间模式上的约束时，肢体间的协调是自组织的。这项拟议的研究将对运动过程中控制肢体间协调的神经力学机制提供新的深入理解。这一点具有特别重要的意义，因为了解神经和生物力学系统如何在真实运动中相互作用以动态协调肢体，对于设计生物逼真的机器人和高效的神经假体设备以及最大限度地提高运动成绩和运动康复至关重要。

Interlimb coordination is essential for dynamic stability when navigating in an ever-changing environment and to change locomotor speed, involving complex dynamic interactions at different levels of the central nervous system and emergent properties of the musculoskeletal system. Despite its obvious importance, the dynamic control of interlimb coordination is poorly defined in terrestrial mammals. The long-term goal of my research program is to elucidate neurophysiological and biomechanical mechanisms that control interlimb coordination during locomotion. To accomplish this goal, cats are trained to step on a treadmill with four separate surfaces whereby the speed of the forelimbs and hindlimbs or of the left and right sides are independently controlled. The belts can operate at the same speed (tied-belt locomotion) or at different speeds (split-belt locomotion). Thus, speed or speed differences between limbs can be systematically manipulated to challenge interlimb coordination, revealing adaptive mechanisms. Chronic implantations are used to record muscle activity and evoke reflexes while three-dimensional motion capture acquires detailed locomotor kinematics. Comparisons are made in intact and spinal-transected cats to define the contribution of spinal mechanisms in coordinating the limbs. The FIRST OBJECTIVE is to characterize reflex modulation during tied-belt and split-belt locomotion. Reflexes are essential to quickly adjust to external perturbations. We hypothesize that reflex amplitude 1) will be modulated with task and 2) will be less variable on a step-by-step basis during split-belt locomotion. We also hypothesize that results will be similar in intact and spinal cats, indicating that reflex modulation is primarily determined at a spinal level. The SECOND OBJECTIVE is to characterize patterns of muscle activity during tied-belt and split-belt locomotion. We hypothesize that 1) muscle synergies make use of the bifunctional nature of some muscles, 2) synergies can extend to more than one limb and 3) they are primarily controlled at a spinal level. The THIRD OBJECTIVE is to characterize the dynamic coordination within and between limbs during tied-belt and split-belt locomotion. We hypothesize that interlimb coordination self-organizes when adjusting to speed and to constraints imposed on the interlimb pattern. The proposed research will provide a new depth of understanding on the neuromechanical mechanisms that control interlimb coordination during locomotion. This is of particular significance because knowledge of how the neural and biomechanical systems interact to dynamically coordinate the limbs during real movements is crucial for designing biologically realistic robots and efficient neuroprosthetic devices as well as for maximizing athletic performance and motor rehabilitation.