WASHINGTON — Paralyzed rats learned to walk, run and spring deftly over obstacles after they were put on a physical training regimen that included electrical and chemical stimulation of their broken spinal columns and a “robotic postural interface,” a new study reveals.
The study, published Thursday in Science, suggests that for humans with spinal cord injury, the trick to regaining lost movement may lie not in regeneration of the severed spinal cord, but in inducing the brain and spinal cord to forge wholly new paths toward each other. The Swiss authors liken that process to the way that infants, their nervous systems incomplete and learning by experience, sync up their brains and limbs so they can progressively crawl, stand, walk and play.
All told, 250,000 Americans live with spinal cord injury, and just over half — 52 percent — are paraplegic. Each year, 11,000 new injuries occur — overwhelming in young males.
In this study, coaxing that neural reinvention along took four key components: a soup of neurotransmitters — serotonin, dopamine and norepinephrine — injected into the epidural space; a set of electrodes supplying a continuous flow of electrical energy near the site of the break in the spinal cord; a rehabilitation rig that supports the unsteady participant and initially forces movement of the legs; and a training course that is as real-world as possible.
After five to six weeks of training on uneven and irregular terrain, all 10 rats used in the study regained the capacity to walk voluntarily “and even to sprint up a staircase,” says study co-author Gregoire Courtine, a research scientist in spinal cord repair at the Ecole Polytechnique Federale de Lausanne in Switzerland.
“It was pretty exciting,” he said in an interview Thursday.
The experiment brought together many disparate threads of rehabilitation research and was several years in the making. Its 10 rats were paralyzed in a way that mimics many spinal cord injuries that result in paralysis of the lower limbs: The spinal cord is partially severed at two separate but neighboring sites, leaving intact tissue but interrupting the passage of messages from the brain to the legs.