In 2014, engineering professor Chad Bouton got a lesson on the importance of touch.
Bouton, an engineer at the Feinstein Institutes for Medical Research on Long Island, had developed a brain-computer interface that allowed a man living with paralysis to control one hand.
"He was trying to pick something up and said, 'You know, Chad, I can't feel this object,'" Bouton says. "At that moment we realized, wow, that's what we need to work on next."
More than a decade later, Bouton's team at Feinstein, a part of Northwell Health, is testing a system that can restore both movement and sensation in a paralyzed hand. It also is producing benefits that persist even when the user is no longer connected.
The first person to try the new system was Keith Thomas, who was left paralyzed and without sensation from the chest down after a diving accident in 2020.
"They hooked me up to the machine and I felt my index finger," Thomas says. "It was like, 'whoa!' "
A double neural bypass
In 2023, the team at Feinstein implanted two sets of computer chips in Thomas's brain. One set detects signals coming from areas that control movement. The other delivers signals to areas that process touch and pressure.
These chips are wired to twin pedestals on Thomas's head, which allow his brain to interact with an array of electronics needed to animate his right hand. Right now, this only happens in Bouton's lab, where Thomas spends several hours, twice a week.
The technology is all part of what Bouton calls a "double neural bypass." The first branch bypasses the damaged area of Thomas's spinal cord.
"We are literally rerouting signals from the brain to muscles that are affected," Bouton says. This branch of the bypass also carries signals back to the brain from sensors on Thomas's palm, thumb and index finger.
But that's just half the story.
"We have a second branch that reconnects the brain to the spinal cord," Bouton says. "As someone thinks about moving again, we stimulate the spinal cord based on their thoughts."
This spinal stimulation, which occurs in sync with stimulation of the relevant muscles, amplifies and strengthens the remaining natural connections between the brain and an affected limb.
A team effort
It takes about half a dozen people and a roomful of equipment to animate Thomas's right hand for a few hours.
"The first thing we do is greet him with a smile," says project manager Erona Ibroci. "We say, 'Hey, what's up? Thank you for coming.' "
Then electrical engineers Aniket Jangam and Zeev Elias screw on a pair of NeuroPlex E adapters to the pedestals on Thomas's head. Next, they plug in cables that go to amplifiers, signal processors and, ultimately, a computer.
The system includes artificial intelligence that has learned to recognize the brainwaves Thomas produces when he thinks about moving his paralyzed hand. It also includes sensors that go on his palm, thumb and index finger to provide a sense of touch.
Once Thomas is wired up, the real work begins.
During every session, "we do mobility testing, we do strength testing," says Dana Fried, an occupational therapist.
Research scientist Santosh Chandrasekaran points to a monitor showing two animated hands. One indicates the motion Thomas is supposed to carry out. The other is controlled by Thomas's brain.
"He cannot move his own hand, but he's trying to do that," Chandrasekaran says. "The decoder figures out what he's thinking about and then controls the other hand on the screen."
The decoder also sends signals to the muscles controlling Thomas's actual hand, causing it to move in sync with its on-screen avatar.
Thomas has much better control of his hand when he is receiving feedback from the sensors on his hand, Chandrasekaran says.
"What we are measuring is the force levels on the sensor," he says. "And then appropriately stimulating the right electrodes in the brain so that we can make him feel a sensory percept at the right location on the hand."
Lasting benefits
The double bypass allowed Thomas to feel his sister's hand when she made a visit to the lab. "The sensation was like "a rush of energy," he says.
Another milestone came when the team put a cup of water in front of him.
"He lifted that cup up, for the first time, to his mouth, took a drink and then set it back down all on his own without any help," Bouton says.
Over time, Thomas also has gotten better at interpreting the sensory feedback from his hand even when he can see what it's touching.
"I'd be like, 'hmmm, it's a tennis ball' or something heavier or something lighter," he says.
At first, the improvements were only present when Thomas was hooked up to the equipment in Bouton's lab. But after more than a year of therapy and spinal stimulation, Thomas is able to do more — and feel more — at home.
During a Zoom conversation, Thomas shows me how he can now lift his arm up unassisted.
His increased strength and mobility allow him to do things like pet his dog. And when he does, he says, "I can feel a little bit of the fur."
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