A device that assumes total control of a paralyzed rat’s lower spinal cord could hold the key to developing effective solutions for humans suffering from paralysis, a new study finds. Whatever function was lost due to injury or electrical error, the device can restore it.

Spinal cord stimulation has been the go-to method for restoring limb function for years. And before that, deep brain stimulation was helping patients suffering from neurological disorders, like Parkinson’s disease, to regain stable brain function. But so far, spinal cord stimulation has been limited to minor movements — flexing one’s toes or supporting the body’s weight when standing upright. The new results, from EPFL in Switzerland, suggest a more robust potential.

"We have complete control of the rat's hind legs," said EPFL neuroscientist Grégoire Courtine in a statement. "The rat has no voluntary control of its limbs, but the severed spinal cord can be reactivated and stimulated to perform natural walking. We can control in real-time how the rat moves forward and how high it lifts its legs."

Courtine and his team hooked the rats up to a tiny, rat-sized harness that secured the animal in place. A mix of pharmacological cocktail and electrical impulses delivered straight to the spinal cord allowed the scientists to dial the frequencies either up or down, depending on the desired gait. When walking on a treadmill, the rats’ normal stride was fluid and even, unlike prior studies that have managed only to achieve choppy, halting steps.

The scientists discovered how high a rat raises its legs correlated with the frequency of the device. Eventually this led to a specific pattern of stimulation that allowed the animal to perform a complex movement. Even when the rats were made to walk up a miniature staircase — a movement defined by changes in height and step length — the frequencies adjusted accordingly.

The culmination of a decade of research, Courtine says the technology will be ready for clinical trials by the summer of 2015. If each of the processes works in the same fashion as in the rat models, then the anticipated success of human usage can pave the way for prosthetics and rehabilitation regimens. Study co-author and neuroengineer Silvestro Micera pointed to the simple discovery of stimulating the spinal cord, via frequency modulation, as a hallmark of the field.

"We believe that this technology could one day significantly improve the quality of life of people confronted with neurological disorders,” he said.

Human trials will be moved out of the rat lab and into EPFL’s 100-square meter research facility. When a patient straps into the harness, equipped with two reflective sensors, he or she also steps onto a treadmill, known as the Gait Platform, surrounded by 14 infrared cameras designed to capture the patient’s every move. Courtine and the rest of the EPFL scientists on the project will be working closely with physiotherapists and doctors at the University Hospital of Lausanne to better interpret the results.

“My team and I are aware that we have not found a cure for spinal cord injury,” Courtine said, “but we have now gathered all the knowledge and technology to extend this treatment of laboratory rats to spinal cord-injured people using this innovative Gait Platform.”

Source: Wenger N, Moraud E, Raspopovic S, et al. Closed-loop neuromodulation of spinal sensorimotor circuits controls refined locomotion after complete spinal cord injury. Neurotechnology. 2014.