Introduction to the Special Issue on Locomotor Rehabilitation after Spinal Cord Injury

[...]questions that must be answered include what, exactly, is lost after SCI and how can retraining help to recover or replace that which was lost? A most revealing study that investigated the function of the pattern generating network after spinal cord injury arrived in 1996 from the laboratory of Serge Rossignol.1 This study stands out by making several key points. The beautiful stepping that develops using this approach is kinematically and electrophysiologically very similar to intact animals, but it does not translate to improved function when the animal is removed from the apparatus because step-trained animals lack balance in an open field. [...]while the isolated locomotor circuitry is rapidly able to initiate near-normal hindlimb stepping when training is initiated acutely, additional strategies appear to be necessary for this capacity to be meaningful for overground locomotion. All the animals regained frequent to consistent weight-supported hindlimb stepping by six to eight weeks post-injury whether they were trained in shallow water or not, presumably due to self-training in their cages. [...]regaining weight support rapidly post-injury allowed the pattern-generating capacity to be expressed, and animals recovered good quality hindlimb stepping. [...]the capacity of the spinal cord circuitry to generate weight support is lost immediately after the injury but can recover with an acute combination of therapies, including training. [...]without acute retraining, subjects lacking the ability to retrain themselves because of a high center of gravity can reach a state where both pattern generation and weight support are compromised and need to be provided/retrained.