With brain training, paraplegics can once again move and sense their limbs despite having spinal cord injuries that were previously considered irreversible, an international team of researchers reports Thursday in Scientific Reports.

After a year of working with a brain-machine interface, virtual reality, and robotic exoskeletons, eight paraplegic patients began moving and feeling their lower bodies again. Some can now even walk with assistance. Half of them were upgraded from a classification of ‘complete’ paralysis to incomplete. And this group has continued to train and improve, according to the lead study author, Miguel Nicolelis, of Duke University.

“Nobody ever imagined that one day we would be talking about the possibility of using brain-machine interfaces to induce partial neurological recovery in patients who have been diagnosed as having a complete spinal cord injury,” Nicolelis told press during a conference call. “As you can imagine, for us this is a very important milestone."

Originally, Nicolelis and his colleagues had a humbler goal of helping paralyzed patients move around with mind-controlled robotic assistance—like high-tech walkers. They developed their own brain-machine interfaces, which intercept brain signals relating to motion and convert them into commands for robotic limbs, exoskeletons, or even actual limbs. With the help of immersive virtual reality training, the patients imagined themselves walking and moving and could actually pull it off with their robotic exoskeletons and assistance. But after seven months, something unexpected happened: researchers noted that the training seemed to be spurring the patients’ nervous systems to actually recover.

Until then, Nicolelis and colleagues had considered the technology “assistive” to their paralyzed patients, not rehabilitative. Yet, the patients’ partial recovery squares with previous studies that found that up to 80 percent of paralyzed patients still have functioning neural circuitry past their injuries. It also fits with other studies that have found twitches of recovery in other paralyzed patients that used such brain-machine interfaces.

Still, Nicolelis said theirs is the first study to document such recovery, which occurred over the course of 2014. The eight patients involved had suffered devastating spinal cord injuries three to 13 years prior to that and had signed up for the study to help refine an assistive mind-controlled exoskeleton. They showed up at a Neurorehabilitation Laboratory in São Paulo, Brazil twice a week for hour-long training sessions. They also went through standard physical therapy.

All of the patients showed improvement, regaining sensation and some movement in their limbs and body parts below their injuries. The researchers noted the recovery of voluntary movement in key muscles as well as the patients’ bowels. After 10 months, one patient went from not being able to stay standing when put in position in braces to being able to walk using a walker, braces, and therapist assistance.

While more research will be needed to validate and unpack what was going on in the patients, Nicolelis has a theory of how their recovery happened. The combination of technology that forced patients to imagine movement while pulling them up and actually moving them recharged dormant neural circuits that had survived the injury, he said.

If the theory holds up and researchers can figure out cheaper ways to pull it off, Nicolelis envisions future treatments of brain training and stem cell injections that could repair and enliven nerves for patients to make full recoveries.

Scientific Reports, 2016. DOI: 10.1038/srep30383 (About DOIs).