Adaptive mechanisms coupling the four limbs during quadrupedal locomotion

在包括人类在内的陆生哺乳动物中，行走涉及到四肢的协调活动。尽管行走过程中协调手臂和腿的机制尚不清楚，但人们认为位于脊髓颈段和腰椎水平的功能网络之间存在联系。这项研究的目的是研究猫在四足跑步机运动时，在这些网络功能上可以解耦的情况下，将脊髓的颈椎和腰椎网络耦合起来的一些反射通路。为了实现这一目标，将在四向分体式跑步机上研究四足动物的运动，这种跑步机可以分离每条腿的节奏(即速度)，从而分离控制每条腿的脊柱网络的功能。猫将被植入记录和刺激电极，分别记录四肢的肌肉活动和刺激周围神经。神经刺激将被用来唤起将手臂和腿连接起来的反射反应。例如，供应足背和前爪的神经将受到刺激，分别在前肢和后肢的肌肉中唤起反射反应。目标是研究四足行走时的这些反射路径，当四肢以相同的速度行走，并且在使用各种组合独立控制每条肢体的节奏的情况下。这种方法将展示反射通路如何在这些条件下适应，并提供关于感觉反馈在调节位于一条腰带(例如手臂)到另一条腰带(例如腿)的网络活动中的作用的机械性见解。这些实验数据将为系统研究参与四足动物运动控制和适应的神经结构提供一个框架。

In terrestrial mammals, including humans, walking involves coordinated activity of all four limbs. Although mechanisms coordinating the arms and legs during walking are poorly understood, it is thought that a linkage between functional networks located at the cervical and lumbosacral levels of the spinal cord are involved. The goal of this study is to investigate some of the reflex pathways that couple the cervical and lumbosacral networks of the spinal cord during quadrupedal treadmill locomotion in the cat, in conditions where these networks can be functionally uncoupled. To accomplish this goal, quadrupedal locomotion will be studied on a 4-way split-belt treadmill that can uncouple the rhythm (i.e. speed) of each leg, thus separating the functioning of the spinal networks controlling each limb. Cats will be implanted with recording and stimulating electrodes to record muscular activity in all four limbs and to stimulate peripheral nerves, respectively. The nerve stimulation will be done to evoke reflex responses that couple the arms and legs. For instance, the nerves supplying the dorsum of the foot and forepaw will be stimulated to evoke reflex responses in muscles of the forelimbs and hindlimbs, respectively. The goal is to study these reflex pathways during quadrupedal locomotion when the four limbs walk at the same speed and under conditions where the rhythm of each limb is independently controlled using various combinations. Such an approach, will demonstrate how reflex pathways adapt under these conditions, and also provide mechanistic insight as to the role of sensory feedback in regulating the activity of networks located at one girdle (e.g. arms) to another (e.g. legs). The experimental data will provide a framework to systematically investigate the neural structures involved in the control and adaptation of quadrupedal locomotion.