Kuczynski Victoria, Telonio Alessandro, Thibaudier Yann, Hurteau Marie-France, Dambreville Charline, Desrochers Etienne, Doelman Adam, Ross Declan, Frigon Alain
Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Quebec, Canada, J1H 5N4.
J Physiol. 2017 Sep 1;595(17):5987-6006. doi: 10.1113/JP274518. Epub 2017 Jul 18.
During split-belt locomotion in humans where one leg steps faster than the other, the symmetry of step lengths and double support periods of the slow and fast legs is gradually restored. When returning to tied-belt locomotion, there is an after-effect, with a reversal in the asymmetry observed in the early split-belt period, indicating that the new pattern was stored within the central nervous system. In this study, we investigated if intact and spinal-transected cats show a similar pattern of adaptation to split-belt locomotion by measuring kinematic variables and electromyography before, during and after 10 min of split-belt locomotion. The results show that cats do not adapt to prolonged split-belt locomotion. Our results suggest an important physiological difference in how cats and humans respond to prolonged asymmetric locomotion.
In humans, gait adapts to prolonged walking on a split-belt treadmill, where one leg steps faster than the other, by gradually restoring the symmetry of interlimb kinematic variables, such as double support periods and step lengths, and by reducing muscle activity (EMG, electromyography). The adaptation is also characterized by reversing the asymmetry of interlimb variables observed during the early split-belt period when returning to tied-belt locomotion, termed an after-effect. To determine if cats adapt to prolonged split-belt locomotion and to assess if spinal locomotor circuits participate in the adaptation, we measured interlimb variables and EMG in intact and spinal-transected cats before, during and after 10 min of split-belt locomotion. In spinal cats, only the hindlimbs performed stepping with the forelimbs stationary. In intact and spinal cats, step lengths and double support periods were, on average, symmetric, during tied-belt locomotion. They became asymmetric during split-belt locomotion and remained asymmetric throughout the split-belt period. Upon returning to tied-belt locomotion, symmetry was immediately restored. In intact cats, the mean EMG amplitude of hindlimb extensors increased during split-belt locomotion and remained increased throughout the split-belt period, whereas in spinal cats, EMG amplitude did not change. Therefore, the results indicate that the locomotor pattern of cats does not adapt to prolonged split-belt locomotion, suggesting an important physiological difference in the control of locomotion between cats and humans. We propose that restoring left-right symmetry is not required to maintain balance during prolonged asymmetric locomotion in the cat, a quadruped, as opposed to human bipedal locomotion.
在人类的分带式行走中，当一条腿比另一条腿迈得更快时，慢腿和快腿的步长及双支撑期的对称性会逐渐恢复。当恢复到系带宽腰带行走时，会出现一种后效应，即在分带早期观察到的不对称性会发生反转，这表明新模式已存储在中枢神经系统中。在本研究中，我们通过测量完整和脊髓横断猫在分带式行走前、行走期间和行走后10分钟的运动学变量和肌电图，来研究它们是否表现出类似的对分带式行走的适应模式。结果表明，猫不会适应长时间的分带式行走。我们的结果表明，猫和人类对长时间不对称行走的反应存在重要的生理差异。
在人类中，步态会通过逐渐恢复肢体间运动学变量（如双支撑期和步长）的对称性以及减少肌肉活动（肌电图，EMG），来适应在分带跑步机上的长时间行走，其中一条腿比另一条腿迈得更快。这种适应的另一个特征是，在恢复到系带宽腰带行走时，会反转在分带早期观察到的肢体间变量的不对称性，这被称为后效应。为了确定猫是否适应长时间的分带式行走，并评估脊髓运动回路是否参与这种适应过程，我们在完整和脊髓横断的猫进行10分钟分带式行走的前、中、后测量了肢体间变量和肌电图。在脊髓猫中，只有后肢在进行踏步，前肢保持静止。在完整和脊髓猫中，在系带宽腰带行走期间步长和双支撑期平均是对称的。在分带式行走期间它们变得不对称，并在整个分带期保持不对称。恢复到系带宽腰带行走时，对称性立即恢复。在完整猫中，后肢伸肌的平均肌电图振幅在分带式行走期间增加，并在整个分带期保持增加，而在脊髓猫中，肌电图振幅没有变化。因此，结果表明猫的运动模式不会适应长时间的分带式行走，这表明猫和人类在运动控制方面存在重要的生理差异。我们提出，在猫这种四足动物的长时间不对称行走中，与人类两足行走不同，维持平衡并不需要恢复左右对称性。
