de Leon R D, Hodgson J A, Roy R R, Edgerton V R
Department of Physiological Science, UCLA, Los Angeles, California 90095, USA.
J Neurophysiol. 1998 Mar;79(3):1329-40. doi: 10.1152/jn.1998.79.3.1329.
Locomotor performance, hindlimb muscle activity and gait patterns during stepping were studied in step-trained and non-trained female, adult spinal cats. Changes in locomotor characteristics relative to prespinalization bipedal and quadrupedal stepping patterns were used to evaluate the effects of step training on the capacity to execute full weight-bearing stepping after spinalization. Step training consisted of full weight-bearing stepping of the hindlimbs at the greatest range of treadmill speeds possible at any given stage of locomotor recovery. In the initial stages of training the limbs were assisted as needed to execute successful steps. On the basis of two behavioral criteria, the maximum speed of treadmill stepping and the number of successful steps per unit time, the ability to step was at least 3 times greater in animals trained to step versus those allowed to recover spontaneously, i.e., the non-trained. The greater success in stepping was reflected in several physiological and kinematic properties. For example, the amplitude of electromyograph (EMG) bursts in the tibialis anterior (an ankle dorsiflexor), the amount of extension at the end of both the stance (E3) and swing (E1) phases of the step cycle, and the amount of lift of the hindlimb during swing were greater in step-trained than in non-trained spinal cats. The changes that occurred in response to training reflected functional adaptations at specific phases of the step cycle, e.g., enhanced flexor and extensor function. The improved stepping capacity attributable to step training is interpreted as a change in the probability of the appropriate neurons being activated in a temporally appropriate manner. This interpretation, in turn, suggests that step training facilitated or reinforced the function of extant sensorimotor pathways rather than promoting the generation of additional pathways. These results show that the capacity of the adult lumbar spinal cord to generate full weight-bearing stepping over a range of speeds is defined, in large part, by the functional experience of the spinal cord after supraspinal connectivity has been eliminated. These results have obvious implications with regards to 1) the possibility of motor learning occurring in the spinal cord; 2) the importance of considering "motor experience" in assessing the effect of any postspinalization intervention; and 3) the utilization of use-dependent interventions in facilitating and enhancing motor recovery.
对经过阶梯训练和未经过训练的成年雌性脊髓猫在行走过程中的运动表现、后肢肌肉活动和步态模式进行了研究。相对于脊髓损伤前的双足和四足行走模式，运动特征的变化用于评估阶梯训练对脊髓损伤后执行全负重行走能力的影响。阶梯训练包括在运动恢复的任何给定阶段，使后肢在跑步机最大速度范围内进行全负重行走。在训练的初始阶段，根据需要辅助肢体以执行成功的步骤。基于两个行为标准，即跑步机行走的最大速度和单位时间内成功步骤的数量，经过阶梯训练的动物的行走能力比那些自发恢复的动物（即未经过训练的动物）至少大三倍。行走方面更大的成功体现在几个生理和运动学特性上。例如，胫前肌（踝关节背屈肌）肌电图（EMG）爆发的幅度、步周期支撑期（E3）和摆动期（E1）结束时的伸展量以及摆动期间后肢的抬起量，经过阶梯训练的脊髓猫比未经过训练的更大。对训练产生的变化反映了步周期特定阶段的功能适应，例如增强的屈肌和伸肌功能。归因于阶梯训练的行走能力改善被解释为适当神经元以时间合适的方式被激活的概率发生了变化。反过来，这种解释表明阶梯训练促进或加强了现存感觉运动通路的功能，而不是促进额外通路的产生。这些结果表明，成年腰段脊髓在一定速度范围内产生全负重行走的能力在很大程度上由脊髓在脊髓以上连接被消除后的功能经验所决定。这些结果对于以下方面具有明显的意义：1）脊髓中发生运动学习的可能性；2）在评估任何脊髓损伤后干预的效果时考虑“运动经验”的重要性；3）利用依赖使用的干预措施来促进和增强运动恢复。
