Dr. Robert Gaunt and Dr. Jennifer Collinger look on as President Barack Obama shares a fist bump with Nathan Copeland at the White House Frontiers Conference. | University of Pittsburgh
Thanks to a brain implant, a man with paralysis has regained a sense of touch in his hand, sensations that he described as mimicking natural touch, according to a new study in the 19 October issue of Science Translational Medicine. The device allowed him to control and sense touch through a robotic hand, paving the way to improving neuroprosthetic devices for patients with paralysis, amputations, or stroke.
About 10 years ago, Nathan Copeland was in a car accident that injured his spinal cord, leaving him paralyzed in the arms and legs. Now 28 years old, Copeland used a robotic arm to shake hands and fist-bump President Barack Obama at the 13 October White House Frontiers Conference in Pittsburgh, Pennsylvania.
“If you take away someone’s sensations, they actually have a very hard time doing anything at all,” said Michael Boninger of the University of Pittsburgh. “For us to really get the promise of neuroprosthetics, we need to get to the point where we are integrating both the motor side of the human body and the sensory side of the human body.”
The study “takes a huge step” toward that goal, said Boninger.
Copeland underwent brain surgery, in which four small electrodes were implanted into the somatosensory cortex, the part of the brain that controls touch. The chips can send electrical signals that directly stimulate brain cells in this region to recreate the perception of touch, bypassing Copeland’s spinal cord injury.
While the technique, known as intracortical microstimulation, has proven promising in animal studies, "what was unknown previously was how that would feel like in humans,” said Boninger.
Electrical signals delivered through the brain implant evoked sensations like pressure or tingling as if they were originating from Copeland’s right hand. He described 93% of the stimuli, such as pressing a cotton swab or the tip of a wooden toothpick on the surface of the skin, as feeling “possibly natural.”
Copeland was also able to sense touch when connected to a prosthetic limb, correctly identifying 84% of the time which individual prosthetic finger was being touched while blindfolded. The sensations remained stable over the course of the six-month study.
“It was unbelievable. It’s just amazing to interact with someone with a robotic arm who could control it just through his thoughts,” said Boninger.
“The most important advance is the fact that this arm now has feedback to the somatosensory cortex so that the individual can now feel that hand being touched or pushed. This feedback is tremendously important,” said Jeremy Berg, editor-in-chief of the Science family of journals. “Consider what it would be like to try to pick something up without being able to feel whether you had grabbed it or not. With the feedback, you can now judge what you are doing by direct mechanisms rather than relying on visual feedback.”
Neuroprosthetic limbs still have a long way to go before they are fully dexterous or allow patients to discern between hot and cold or different textures. Still, the findings lay the groundwork for restoring lifelike sensations in patients with paralysis, amputations, or stroke.
“There’s an amazing potential for the technology to apply for all types of neurological disorders,” said Boninger.