It's a technology that sounds lifted from the latest Marvel movie—a brain-computer interface functional electrical stimulation (BCI-FES) system that enables paralyzed users to walk again. But thanks to neurologists, biomedical engineers and other scientists at the University of California, Irvine, it's very much a reality, though admittedly with only one successful test subject so far.
The team, led by Zoran Nenadic and An H. Do, built a device that translates brain waves into electrical signals than can bypass the damaged region of a paraplegic's spine and go directly to the muscles, stimulating them to move. To test it, they recruited 28-year-old Adam Fritz, who had lost the use of his legs five years earlier in a motorcycle accident.
Fritz first had to learn how exactly he'd been telling his legs to move for all those years before his accident. The research team fitted him with an electroencephalogram (EEG) cap that read his brain waves as he visualized moving an avatar in a virtual reality environment. After hours training on the video game, he eventually figured out how to signal "walk."
The next step was to transfer that newfound skill to his legs. The scientists wired up the EEG device so that it would send electrical signals to the muscles in Fritz's leg. And then, along with physical therapy to strengthen his legs, he would practice walking—his legs suspended a few inches off the ground—using only his brain (and, of course, the device). On his 20th visit, Fritz was finally able to walk using a harness that supported his body weight and prevented him from falling. After a little more practice, he walked using just the BCI-FES system. After 30 trials run over a period of 19 weeks, he could successfully walk through a 12-foot-long course.
As encouraging as the trial sounds, there are experts who suggest the design has limitations. "It appears that the brain EEG signal only contributed a walk or stop command," says Dr. Chet Moritz, an associate professor of rehab medicine, physiology and biophysics at the University of Washington. "This binary signal could easily be provided by the user using a sip-puff straw, eye-blink device or many other more reliable means of communicating a simple 'switch.'"
Moritz believes it's unlikely that an EEG alone would be reliable enough to extract any more specific input from the brain while the test subject is walking. In other words, it might not be able to do much more beyond beginning and ending a simple motion like moving your legs forward—not so helpful in stepping over curbs or turning a corner in a hallway.
The UC Irvine team hopes to improve the capability of its technology. A simplified version of the system has the potential to work as a means of noninvasive rehabilitation for a wide range of paralytic conditions, from less severe spinal cord injuries to stroke and multiple sclerosis.
"Once we've confirmed the usability of this noninvasive system, we can look into invasive means, such as brain implants," said Nenadic in a statement announcing the project's success. "We hope that an implant could achieve an even greater level of prosthesis control because brain waves are recorded with higher quality. In addition, such an implant could deliver sensation back to the brain, enabling the user to feel their legs.
