Department of Biological Sciences, University of Delaware, Wilmington, Delaware.
Department of Natural Science, DeSales University, Center Valley, Pennsylvania.
J Neurophysiol. 2020 Jan 1;123(1):70-89. doi: 10.1152/jn.00018.2019. Epub 2019 Nov 6.
Sensorimotor training providing motion-dependent somatosensory feedback to spinal locomotor networks restores treadmill weight-bearing stepping on flat surfaces in spinal cats. In this study, we examined if locomotor ability on flat surfaces transfers to sloped surfaces and the contribution of length-dependent sensory feedback from lateral gastrocnemius (LG) and soleus (Sol) to locomotor recovery after spinal transection and locomotor training. We compared kinematics and muscle activity at different slopes (±10° and ±25°) in spinalized cats ( = 8) trained to walk on a flat treadmill. Half of those animals had their right hindlimb LG/Sol nerve cut and reattached before spinal transection and locomotor training, a procedure called muscle self-reinnervation that leads to elimination of autogenic monosynaptic length feedback in spinally intact animals. All spinal animals trained on a flat surface were able to walk on slopes with minimal differences in walking kinematics and muscle activity between animals with/without LG/Sol self-reinnervation. We found minimal changes in kinematics and muscle activity at lower slopes (±10°), indicating that walking patterns obtained on flat surfaces are robust enough to accommodate low slopes. Contrary to results in spinal intact animals, force responses to muscle stretch largely returned in both SELF-REINNERVATED muscles for the trained spinalized animals. Overall, our results indicate that the locomotor patterns acquired with training on a level surface transfer to walking on low slopes and that spinalization may allow the recovery of autogenic monosynaptic length feedback following muscle self-reinnervation. Spinal locomotor networks locomotor trained on a flat surface can adapt the locomotor output to slope walking, up to ±25° of slope, even with total absence of supraspinal CONTROL. Autogenic length feedback (stretch reflex) shows signs of recovery in spinalized animals, contrary to results in spinally intact animals.
感觉运动训练为脊髓运动网络提供运动相关的躯体感觉反馈，可恢复脊髓猫在平坦表面上的跑步机承重踏步。在这项研究中，我们研究了在平坦表面上的运动能力是否转移到倾斜表面，以及来自外侧腓肠肌（LG）和比目鱼肌（Sol）的长度依赖性感觉反馈对脊髓横断后和运动训练后的运动恢复的贡献。我们比较了脊髓猫（=8）在平坦跑步机上训练时在不同坡度（±10°和±25°）下的运动学和肌肉活动。这些动物中有一半在脊髓横断和运动训练前切断并重新连接了右后肢 LG/Sol 神经，这一过程称为肌肉自身再神经支配，导致在脊髓完整动物中消除了自主单突触长度反馈。所有在平坦表面上训练的脊髓动物都能够在坡度上行走，具有/不具有 LG/Sol 自身再神经支配的动物之间的行走运动学和肌肉活动差异最小。我们发现较低坡度（±10°）的运动学和肌肉活动变化最小，表明在平坦表面上获得的行走模式足够稳健，可以适应较低的坡度。与脊髓完整动物的结果相反，在受过训练的脊髓化动物中，肌肉拉伸的力反应在 SELF-REINNERVATED 肌肉中基本恢复。总的来说，我们的结果表明，在水平表面上进行训练获得的运动模式可以转移到低坡度行走，并且脊髓化可能允许在肌肉自身再神经支配后恢复自主单突触长度反馈。在平坦表面上接受运动训练的脊髓运动网络可以适应斜坡行走的运动输出，可达±25°的坡度，即使完全没有上位控制。自主长度反馈（牵张反射）在脊髓化动物中显示出恢复的迹象，与脊髓完整动物的结果相反。
