For the first time, scientists have helped a paralyzed man experience the sense of touch through the use of a mind-controlled robotic arm.
The groundbreaking experiment, a collaboration between the University of Pittsburgh and the University of Pittsburgh Medical Center, involves electrodes smaller than a grain of sand implanted in the sensory cortex of the young man’s brain. Researchers then stimulated this region, which is associated with sensation in the right hand, and effectively bypassed his damaged spinal cord. Because the paralyzed man was already connected to a robotic arm, when a researcher pressed the fingers of the prosthesis, the subject felt the pressure in the right fingers of his paralyzed hand.
The results of the experiment, which have been repeated over several months with the subject, offer a critical breakthrough in the recreation and restoration of function in people with paralyzed limbs: the ability not just to move those limbs, but something much more difficult – to feel them.
The research will be featured Thursday afternoon when President Obama visits Pittsburgh for a White House Frontiers Conference on advances in science, medicine and technology.
Nathan Copeland was 18 years old when his car spun out of control on a rainy winter night in 2004. The western Pennsylvania man was diagnosed with tetraplegia, paralysis of all four limbs. Five years ago, he volunteered for a cutting edge experiment at the University of Pittsburgh Medical Center.
A team of researchers including surgeons, biomedical engineers and doctors of rehabilitative medicine, were toiling with the technology that would enable paralyzed individuals not simply to move their limbs again, but to restore sensation to them.
Copeland, who had been studying nanotechnology before his accident, was the perfect subject. Last spring, surgeons implanted four tiny electrodes into his sensory cortex, specifically the region of the brain that controls the sense of touch in the right hand and fingers. By electrically stimulating this region, the researchers were able to bypass Copeland’s damaged spinal cord. Already connected to a mind-controlled robotic arm, Copeland was ready for the experiment to begin. He was blindfolded so that he couldn’t see what researchers were doing, but one by one they touched each of the fingers on the robot’s right hand, and each time Copeland correctly identified the location of the sensation.
“I can feel just about every finger,” Copeland said. “Sometimes it feels electrical, and sometimes it’s pressure, but for the most part, I can tell most of the fingers with definite precision. It feels like my fingers are getting touched or pushed.”
The research team was quietly ecstatic.
“I was awfully relieved, ” said biomedical engineer Robert Gaunt. “Nathan was pretty happy, these were places on the hand that he hasn’t felt in 10 years.”
Prior to this experiment, no robotic limb had allowed a paralyzed person to experience the natural sense of touch, a kind of Holy Grail in rehabilitative medicine. For a prosthetic limb to truly mimic the full functionality of a human one, it needed to be endowed with somatosensory feedback from the paralyzed person’s brain.
The electrical stimulation of peripheral nerves in amputees offers enough sensation to allow for improvements in the control of artificial limbs, but not true sensation. Without a functioning peripheral nerve system, paralyzed people have had no ability to experience any tactile sensations. Mind-controlled robotic arms got them only half way. Able to move and manipulate objects was an advancement, but without the sensation of touch, these prosthetic limb movements were slower and clumsier.
“With Nathan, he can control a prosthetic arm, do a handshake, fist bump, move objects around,” Gaunt said. “And in this [experiment] he can experience sensations from his own hand. Now we want to put those two things together so that when he reaches out to grasp an object he can he feel it. . . He can he pick something up that’s soft and not squash it, or drop it.”
To even get to this point involved massive collaboration with multiple institutions and researchers, said Gaunt. The microelectrode package and control system were developed by Blackrock Microsystems, and the robotic arm by the Applied Physics Lab at Johns Hopkins University. The experiment, which is published Thursday in the journal Science Translational Medicine, lists 10 authors and 10 departments and institutions.
Four years earlier Jennifer Collinger, another member of the team, was involved in the experiment that served as a kind of stepping-stone. Jan Scheurmann, a 36-year-old mother of two, was the volunteer. Scheurmann had been diagnosed with spinocerebellar degeneration, a disease that destroys the connections between the brain and muscles. The Pittsburgh researchers enabled the woman to consistently perform many natural and difficult motions with her arms and hands using a mind-controlled, human-like robot arm. Her goal: to eat a piece of chocolate on her own. She did.
“We’ve been working since 2010 to get to this point, doing the background research, doing the regulatory work, and the pre-surgical involvement,” Collinger said. “For Nathan, he did this with the greater good in mind. He was willing to be the pioneer, and he’s excited to be the very person to feel sensation. And now he’s excited to see how far we can take it.”
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