Harnie Jonathan, Audet Johannie, Mari Stephen, Lecomte Charly G, Merlet Angèle N, Genois Gabriel, Rybak Ilya A, Prilutsky Boris I, Frigon Alain
Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Centre de Recherche du CHUS, Université de Sherbrooke, Sherbrooke, QC, Canada.
Department of Neurobiology and Anatomy, College of Medicine, Drexel University, Philadelphia, PA, United States.
Front Syst Neurosci. 2022 Feb 9;16:814028. doi: 10.3389/fnsys.2022.814028. eCollection 2022.
Locomotion after complete spinal cord injury (spinal transection) in animal models is usually evaluated in a hindlimb-only condition with the forelimbs suspended or placed on a stationary platform and compared with quadrupedal locomotion in the intact state. However, because of the quadrupedal nature of movement in these animals, the forelimbs play an important role in modulating the hindlimb pattern. This raises the question: whether changes in the hindlimb pattern after spinal transection are due to the state of the system (intact versus spinal) or because the locomotion is hindlimb-only. We collected kinematic and electromyographic data during locomotion at seven treadmill speeds before and after spinal transection in nine adult cats during quadrupedal and hindlimb-only locomotion in the intact state and hindlimb-only locomotion in the spinal state. We attribute some changes in the hindlimb pattern to the spinal state, such as convergence in stance and swing durations at high speed, improper coordination of ankle and hip joints, a switch in the timing of knee flexor and hip flexor bursts, modulation of burst durations with speed, and incidence of bi-phasic bursts in some muscles. Alternatively, some changes relate to the hindlimb-only nature of the locomotion, such as paw placement relative to the hip at contact, magnitude of knee and ankle yield, burst durations of some muscles and their timing. Overall, we show greater similarity in spatiotemporal and EMG variables between the two hindlimb-only conditions, suggesting that the more appropriate pre-spinal control is hindlimb-only rather than quadrupedal locomotion.
在动物模型中，完全脊髓损伤（脊髓横断）后的运动通常是在仅后肢运动的条件下进行评估的，前肢处于悬吊状态或放置在固定平台上，并与完整状态下的四足运动进行比较。然而，由于这些动物运动的四足特性，前肢在调节后肢运动模式中起着重要作用。这就提出了一个问题：脊髓横断后后肢运动模式的变化是由于系统状态（完整与脊髓损伤）还是因为运动仅为后肢运动。我们收集了9只成年猫在脊髓横断前后，在完整状态下的四足运动和仅后肢运动以及脊髓损伤状态下的仅后肢运动时，七个跑步机速度下运动过程中的运动学和肌电图数据。我们将后肢运动模式的一些变化归因于脊髓损伤状态，例如高速时站立和摆动持续时间的收敛、踝关节和髋关节的不协调、膝屈肌和髋屈肌爆发时间的切换、爆发持续时间随速度的调节以及某些肌肉中双相爆发的发生率。另外，一些变化与仅后肢运动的性质有关，例如接触时爪子相对于臀部的位置、膝关节和踝关节屈服的幅度、某些肌肉的爆发持续时间及其时间。总体而言，我们发现两种仅后肢运动条件下的时空和肌电图变量更为相似，这表明更合适的脊髓前控制是仅后肢运动而非四足运动。
