Adaptive mechanisms coupling the four limbs during quadrupedal locomotion

陆生哺乳动物，包括人类，走路需要四肢的协调活动。尽管在行走过程中协调胳膊和腿的机制尚不清楚，但人们认为位于颈椎和腰骶水平的脊髓功能网络之间存在联系。本研究的目的是研究猫在四足跑步机上运动时，在这些网络可以功能解耦的情况下，脊髓的颈椎和腰骶网络之间的一些反射通路。为了实现这一目标，四足运动将在一个四向分离带跑步机上进行研究，该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。神经刺激会引起胳膊和腿的反射反应。例如，控制脚背和前爪的神经会受到刺激，分别引起前肢和后肢肌肉的反射反应。目的是研究四足运动时的这些反射通路，当四肢以相同的速度行走时，在每个肢体的节奏通过各种组合独立控制的条件下。这种方法将展示反射通路在这些条件下是如何适应的，并且还提供了关于感觉反馈在调节位于一个腰带（例如手臂）到另一个腰带（例如腿）的网络活动中的作用的机制见解。实验数据将提供一个框架，系统地研究参与控制和适应四足运动的神经结构。

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.