In 2020, Keith Thomas dived into a pool and snapped his spine. The accident left him paralyzed from the chest down and unable to feel and move his arms and legs. Alone and isolated in a hospital room due to the pandemic, he jumped on a “first-of-its-kind” clinical trial that promised to restore some sense of feeling and muscle control using an innovative brain implant.
Researchers designed the implant to reconnect the brain, body, and spinal cord. An AI detects Thomas’ intent to move and activates his muscles with gentle electrical zaps. Sensors on his fingertips shuttle feelings back to his brain. Within a year, Thomas was able to lift and drink from a cup, wipe his face, and pet and feel the soft fur of his family’s dog, Bow.
The promising results led the team at Feinstein Institutes for Medical Research and the Donald and Barbara Zucker School of Medicine at Hofstra/Northwell wondering: If the implant can control muscles in one person, can that person also use it to control someone else’s muscles?
A preprint now suggests such “interhuman” connections are possible. With thoughts alone, Thomas controlled the hand of an able-bodied volunteer using precise electrical zaps to her muscles.
The multi-person neural bypass also helped Kathy Denapoli, a woman suffering from partial paralysis and struggling to move her hand. With the system, Thomas helped her successfully pour water with his brain signals. He even eventually felt the objects she touched in return.
It sounds like science fiction, but the system could boost collaborative rehabilitation, where groups of people with brain or spinal cord injuries work together. By showing rather than telling Denapoli how to move her hand, she’s nearly doubled her hand strength since starting the trial.
“Crucially, this approach not only restores aspects of sensorimotor function,” wrote the team. It “also fosters interpersonal connection, allowing individuals with paralysis to re-experience agency, touch, and collaborative action through another person.”
Smart Bridge
We move without a second thought: pouring a hot cup of coffee while half awake, grabbing a basketball versus a tennis ball, or balancing a cup of ice cream instead of a delicate snow cone.
Under the hood, these mundane tasks activate a highly sophisticated circuit. First, the intention to move is encoded in the brain’s motor regions and the areas surrounding them. These electrical signals then travel down the spinal cord instructing muscles to contract or relax. The skin sends feedback on pressure, temperature, and other sensations back to the brain, which adjusts movement on the fly.
This circuit is broken in people with spinal cord injuries. But over the past decade, scientists have begun bridging the gap with the help of brain or spinal implants. These arrays of microelectrodes send electrical signals to tailored AI algorithms that can decode intent. The signals are then used to control robotic arms, drones, and other prosthetics. Other methods have focused on restoring sensation, a crucial aspect of detailed movement.
Connecting motor commands and sensation into a feedback loop—similar to what goes on in our brains naturally—is gaining steam. Thomas’s implant is one example. Unlike previous implants, the device simultaneously taps into the brain, spinal cord, and muscles.
The setup first records electrical activity from Thomas’s brain using sensors placed in its motor regions. The sensors send these signals to a computer where they’re decoded. The translated signals travel to flexible electrode patches, like Band-Aids, placed on his spine and forearm. The patches electrically stimulate his muscles to guide their movement. Tiny sensors on his fingertips and palm then transmit pressure and other sensations back to his brain.
Over time, Thomas learned to move his arms and feel his hand for the first time in three years.
“There was a time that I didn’t know if I was even going to live, or if I wanted to, frankly. And now, I can feel the touch of someone holding my hand. It’s overwhelming,” he said at the time. “The only thing I want to do is to help others. That’s always been the thing I’m best at. If this can help someone even more than it’s helped me somewhere down the line, it’s all worth it.”
Human Connection
To help people regain their speech after injury or disease, scientists have created digital avatars that capture vocal pitch and emotion from brain recordings. Others have linked up people’s minds with non-invasive technologies for rudimentary human-to-human brain communication.
The new study incorporated Thomas’s brain implant with a human “avatar.” The volunteer wore electrical stimulation patches, wired to his brain, on her forearm.
In training, Thomas watched his able-bodied partner grasp an object, such as a baseball or soft foam ball. He received electrical stimulation to the sensory regions of his brain based on force feedback. Eventually, Thomas learned to discriminate between the objects while blindfolded with up to over 90 percent accuracy. Different objects felt strong or light, said Thomas.
The researchers wondered if Thomas could also help others with spinal cord injury. For this trial, he worked with Denapoli, a woman in her 60s with some residual ability to move her arms despite damage to her spinal cord.
Denapoli voiced how she wanted to move her hand—for example, close, open, or hold. Thomas imagined the movement, and his brain signals wirelessly activated the muscle stimulators on Denapoli’s arm to move her hand as intended.
The collaboration allowed her to pick up and pour a water bottle in roughly 20 seconds, with a success rate nearly triple that of when she tried the same task alone. In another test, Thomas’s neural commands helped her grasp, sip from, and set a can of soda down without spillage.
The connection went both ways. Gradually, Thomas began to feel the objects she touched based on feedback sent to his brain.
“This paradigm…allowed two participants with tetraplegia to engage in cooperative rehabilitation, demonstrating increased success in a motor task with a real-world object,” wrote the team.
The implant may have long-lasting benefits. Because it taps into the three main components of neurological sensation and movement, repeatedly activating the circuit could trigger the body to restore damage. With the implant, Thomas experienced improved sensation and movement in his hands and Denapoli increased her grip strength.
The treatment could also help people who suffered a stroke and lost control of their arms, or those with amyotrophic lateral sclerosis (ALS), a neurological disease that gradually eats away at motor neurons. To be clear, the results haven’t yet been peer-reviewed and are for a very limited group of people. More work is need to see if this type of collaborative rehabilitation—or what the authors call “thought-driven therapy”—helps compared to existing approaches.
Still, both participants are happy. Thomas said the study gave him a sense of purpose. “I was more satisfied [because] I was helping somebody in real life…rather than just a computer,” he said.
“I couldn’t have done that without you,” Denapoli told Thomas.
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