“Surprisingly, it worked pretty much right away,” says Burkhart. In June, after some preliminary tests, he thought about opening and closing his hand. And after years of inaction, it obeyed.
“For years, I had thought about it many, many times, and nothing had happened,” he says. “I wasn’t really able to feel my hand moving but I could see it.” So could the assembled on-lookers: Bouton, Rezai, a few other team members, and Burkhart’s father and sister. “It was a pretty special day,” Burkhart says.
The neuroprosthetic is still limited. It relies on a couple of engineers and a room of computers; “I can’t take it outside the lab or anything like that,” says Burkhart. The system also needs to be carefully calibrated every time it’s used, and it can only be used for a few hours every week.
And yet, in those few hours, Burkhart could move his once-paralyzed hand, rotate his wrist, and pinch his fingers. He could even pick up a bottle, pour its contents into another jar, and stir it with a small stick—a complicated sequence that involves two kinds of grasps (a wide-handed one, and a delicate pinch), and several coordinated movements of hand, wrist, and arm. “It’s not 100 percent natural but it feels right,” he says.
The field of neuroprosthetics has made huge strides of late. Just ten years ago, the team behind BrainGate (a neuroprosthetic, not a neuroscandal) demonstrated that paralyzed people could used implanted electrodes to control a virtual cursor and a rudimentary robotic hand. A quadriplegic woman named Cathy Hutchinson would later use BrainGate to drink from a cup of coffee, brought to her lips with a mentally controlled robotic arm.
But that approach doesn't restore movement to a volunteer’s own limbs. In Burkhart’s case, “we not only decoded brain activity in the motor area of someone who’s paralyzed, but we also linked those signals back to their body,” says Bouton. So far, such a feat has only been accomplished in monkeys, whose arms had been temporarily paralyzed by anesthetic. “This is the first time that it’s been done in humans. We allowed Ian to regain movement in real-time, all through his thoughts.”
“It’s an absolutely wonderful step forward in the field of neuroprosthetics,” adds Elizabeth Tyler-Kabara, a neurosurgeon at the University of Pittsburgh.
After his initial success, Burkhart went through 15 months of training, showing up at the lab for three to four hours at a time, three times a week. He’d think about the movements he was trying to achieve, and the team would record the corresponding activity in his motor cortex. “You really don’t think about moving your hand,” Burkhart says. “Now, I had to focus on it and concentrate. What muscles do I use?”
Bouton’s team used machine-learning algorithms to decode the patterns of brain activity that signified each movement. The electrodes on Burkhart’s arm then recreated those movements by stimulating his muscles in preset sequences. By June, he was moving his hand and wrist. Over the following months, he learned to move individual fingers. “That exceeded all of our expectations.” says Bouton. “We certainly hoped for that and didn’t know when it would happen.”