Stroke victims and other victims of traumatic brain injury (TBI) may one day enjoy restored brain function, as scientists from Case Western Reserve University and University of Kansas Medical Center have successfully tested technology that allowed rat models to regain certain brain functions that had once been lost.

In the United States alone, stroke is the leading cause of death, according to the Centers for Disease Control and Prevention. Each year, roughly 130,000 Americans die of a stroke, comprising one in every 19 deaths that occur. More generally, at least 1.7 million TBIs occur in a given year, remaining a factor among injury-related deaths nearly 31 percent of the time. These grim portraits of mental health motivated researchers to investigate the brain’s ability to regain function, specifically utilizing a brain-machine-brain interface, which bridges the damaged area of the brain to relay signals across injury.

The research team used the interface to create a closed-loop system. When a signal runs through the brain, typically if it hits a damaged area it will stop dead, and the signal won’t get received. But bypassing this afflicted area with the artificial interface allows the system to process neural information in real-time and send the information across to the other side, where it can reach its intended destination.

"If you use the device to couple activity from one part of the brain to another, is it possible to induce recovery from TBI? That's the core of this investigation," Pedram Mohseni, professor of electrical engineering and computer science at Case Western Reserve and the brain prosthesis’ builder, said in a statement.

The current study used the prosthetic to test whether rats with damaged anterior and posterior parts of their brain, the ones specifically controlling the animals’ forelimbs, could regain function through use of the prosthesis. Researchers implanted two microelectrodes in the rat’s brain, one on either side of the injured site. Each electrode backed up to a small circuit board, roughly the size of a quarter, which read the incoming signals and transferred them from one electrode to another. An algorithm developed by the researchers teased out the cognitive noise from the signals, which are known as neural action potentials, as they’re produced by the neurons in the anterior of the brain.

After a mere two weeks of running the prosthetic, the rats had regained nearly full use of their forelimbs in all tasks, retrieving the desired food pellet 70 percent of the time. Researchers were pleased with this result, as normal rats demonstrated similar success rates. And to Mohseni’s initial question: “We found that, yes, it is possible to use a closed-loop neural prosthesis to facilitate repair of a brain injury,” he explained.

Several things remain to be tested. The most relevant is whether the device will work on human models. But the most immediate is how long the prosthetic must run before it can be removed, and for how long will it maintain efficacy after removal. Often, neuronal connection is strengthened when the individual neurons can communicate for sustained periods of time. "A question still to be answered is: must the implant be left in place for life?" Mohseni said. "Or can it be removed after two months or six months, if and when new connections have been formed in the brain?"