Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Quebec, J1H 5N4, Canada.
J Physiol. 2019 Jan;597(1):333-350. doi: 10.1113/JP277018. Epub 2018 Nov 10.
The control of locomotion is thought to be generated by activating groups of muscles that perform similar actions, which are termed muscle synergies. Here, we investigated if muscle synergies are controlled at the level of the spinal cord. We did this by comparing muscle activity in the legs of cats during stepping on a treadmill before and after a complete spinal transection that abolishes commands from the brain. We show that muscle synergies were maintained following spinal transection, validating the concept that muscle synergies for locomotion are primarily controlled by circuits of neurons within the spinal cord.
Locomotion is thought to involve the sequential activation of functional modules or muscle synergies. Here, we tested the hypothesis that muscle synergies for locomotion are organized within the spinal cord. We recorded bursts of muscle activity in the same cats (n = 7) before and after spinal transection during tied-belt locomotion at three speeds and split-belt locomotion at three left-right speed differences. We identified seven muscles synergies before (intact state) and after (spinal state) spinal transection. The muscles comprising the different synergies were the same in the intact and spinal states as well as at different speeds or left-right speed differences. However, there were some significant shifts in the onsets and offsets of certain synergies as a function of state, speed and left-right speed differences. The most notable difference between the intact and spinal states was a change in the timing between the knee flexor and hip flexor muscle synergies. In the intact state, the knee flexor synergy preceded the hip flexor synergy, whereas in the spinal state both synergies occurred concurrently. Afferent inputs also appear important for the expression of some muscle synergies, specifically those involving biphasic patterns of muscle activity. We propose that muscle synergies for locomotion are primarily organized within the spinal cord, although their full expression and proper timing requires inputs from supraspinal structures and/or limb afferents.
运动的控制被认为是通过激活执行相似动作的肌肉群来产生的，这些肌肉群被称为肌肉协同作用。在这里，我们研究了肌肉协同作用是否在脊髓水平上受到控制。我们通过比较猫在跑步机上行走前后的腿部肌肉活动来做到这一点，在完全脊髓横切后，大脑的命令被废除。我们表明，在脊髓横切后肌肉协同作用得以维持，验证了运动的肌肉协同作用主要由脊髓内神经元回路控制的概念。
运动被认为涉及功能模块或肌肉协同作用的顺序激活。在这里，我们测试了运动的肌肉协同作用是在脊髓内组织的假设。我们在三条速度的系绳带运动和三条左右速度差异的分裂带运动期间，在相同的猫（n=7）之前和之后记录肌肉活动的爆发，在脊髓横切之前（完整状态）和之后（脊髓状态）。我们在完整状态和脊髓状态下以及在不同速度或左右速度差异下鉴定了七个肌肉协同作用。然而，某些协同作用的起始和结束确实存在一些显著的变化，这是状态、速度和左右速度差异的函数。完整状态和脊髓状态之间最显著的区别是膝屈肌和髋屈肌协同作用之间的时间变化。在完整状态下，膝屈肌协同作用先于髋屈肌协同作用，而在脊髓状态下，两个协同作用同时发生。传入输入似乎对某些肌肉协同作用的表达也很重要，特别是那些涉及肌肉活动双相模式的协同作用。我们提出，运动的肌肉协同作用主要在脊髓内组织，尽管它们的完全表达和适当的时间需要来自中枢神经系统结构和/或肢体传入的输入。
