Control of locomotor activity in humans and animals in the absence of supraspinal influences.

Electrical epidural stimulation of the dorsal surface of the spinal cord at the level of the second lumbar segment induced step-like movements accompanied by the corresponding electromyographic activity in the leg muscles in patients lacking supraspinal influences as a result of vertebral trauma. Triggering of stepping movements was shown to occur with particular stimulation parameters. The results provide evidence that in humans, as in other mammals, the spinal cord contains a network of interneurons acting as generators of stepping movements and producing coordinated patterns of movement activity. Experiments on chronic spinal cats demonstrated the leading role of the propriospinal system of the spinal cord inactivating the spinal generators of stepping in response to epidural stimuli.