Rats paralyzed by spinal-cord injury can learn to control their hind limbs again if they are trained to walk in a rehabilitative device while their lower spine is electrically and chemically stimulated. A clinical trial using a similar system built for humans could begin in the next few years.
Researchers in Switzerland used electrical and chemical stimulation to excite neurons in the lower spinal cord of paralyzed rats while the rodents were suspended by a vest that forced them to walk using only their hind legs. The rehabilitative procedure led to the creation of new neuronal connections between the movement-directing motor cortex of the brain and the lower spine, the researchers report in Science.
Previous research has shown that it is possible to reverse some of the effects of spinal-cord injury by circumventing the normal connection between the brain and legs, which is broken by the injury. For example, walking can be triggered in spinal-cord-injured rats if their spine is stimulated. But until now, such movement has been involuntary. This new research shows that with a specialized training system, similar rats can regain voluntary control over their legs.
A report published last year showed the proof of principle "that this kind of approach can work in patients," says Grégoire Courtine
, senior author of the rat study. In May 2011, 25-year-old Rob Summers, who had been paralyzed from the chest down in a car accident, was reported to stand on his own
for a few minutes with electrical stimulation of his spinal cord. He could also take repeated steps on a treadmill with the stimulation, which activates regions in the lower spinal cord that control walking. The locomotion resulting from this kind of stimulation is automatic and involuntary and is thought to require no direct communication from the brain.