Scientists recently used treadmill exercise, drugs, and electrical stimulation to train paralyzed rats to walk once again, demonstrating a way to possibly treat spinal injuries in humans, which at present are basically untreatable. In a spinal injury, the neural circuits connecting the brain to the muscles that control walking become damaged or severed, leaving an individual paralyzed.
In able-bodied people, these "walking circuits" spring into action when they receive a signal from the brain, but if the spinal cord is damaged, the message from the brain never arrives. When contact with the brain is lost, the circuits shut down [The Guardian].
In the study, published in Nature Neuroscience, researchers manipulated these circuits and produced movement that was "almost indistinguishable" from normal walking. See for yourself in the embedded video.
Scientists already knew that if an electrical current is applied to a nerve just below the injury, the muscle will contract, meaning that messages from neurons in the brain aren't necessarily required to move a muscle. But the act of walking isn't the result of a single stimulation; it relies on a sequence of precise contractions to move a person (or rat) forward. The researchers mimicked this sequence using a combination of drugs, electrical stimulation and training on a treadmill.
The rats, despite having no connection between their brains and their legs, were able to carry their own weight at walking, and even running pace, on a treadmill, with virtually no differences between their gait and the running style of a healthy rat [BBC News].
Well, except for the fact that they are running on their hind legs.
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The researchers note that humans and rats have major structural differences in their spines, but they expect this study will lead them to clinical trials in humans within five years. They say that their technique could help a paralyzed person deliver motor control to their legs, however it doesn't offer a way to control movement with their mind. Instead, a person would rely on a neuroprosthetic device to walk again.