Plasticity properties of CPG circuits in humans: Impact on gait recovery

Recent data on spinal cord plasticity after spinal cord injury (SCI) emphasize the influence of training on determining the functional organization of the spinal circuits that provide the appropriate sequence and intensity of muscular activation needed for gait the so-called central pattern generator (CPG) circuits. This evidence questions the essence of CPG circuits. Are the CPG characteristics innate or are they induced in spinal cord neurons by training? The answer of this question present obvious consequences on the rehabilitative approach to spinal cord injury patients. After briefly reviewing present knowledge on the anatomical and functional organization of spinal CPG in animal models of SCI, data on humans are presented. Evidence indicating that, after SCI, specific functional properties of gait CPG can be induced de novo by specific training in spinal neurons are reported and the hypothesis that CPG circuits may be determined by experience is advanced.