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Quadriplegic patient Nathan Copeland watches a sensor-equipped robotic hand reach out. (Credit: UPMC / Pitt Health Sciences)
A dozen years ago, an auto accident left Nathan Copeland paralyzed, without any feeling in his fingers. Now that feeling is back, thanks to a robotic hand wired up to a brain implant.
“I can feel just about every finger – it’s a really weird sensation,” the 28-year-old Pennsylvanian told doctors a month after his surgery.
Today the brain-computer interface is taking a share of the spotlight at the White House Frontiers Conference in Pittsburgh, with President Barack Obama and other luminaries in attendance.
The ability to wire sensors into the part of the brain that registers the human sense of touch is just one of many medical marvels being developed on the high-tech frontiers of rehabilitation.
“You learn completely new and different things every time you come at this from different directions,” Arati Prabhakar, director of the Pentagon’s Defense Advanced Research Projects Agency, said last week at the GeekWire Summit in Seattle.
Prabhakar provided a preview of the Copeland’s progress during her talk. DARPA’s Revolutionizing Prosthetics program provided the primary funding for the project, which was conducted at the University of Pittsburgh and its medical center, UPMC.
The full details of the experiment were published online today in Science Translational Medicine.
Copeland’s spinal cord was severely injured in an accident in the winter of 2004, when he was an 18-year-old college freshman. The injury left him paralyzed from the upper chest down, with no ability to feel or move his lower arms or legs.
Right after the accident, Copeland put himself on Pitt’s registry of patients willing to participate in clinical trials. Nearly a decade later, a medical team led by Pitt researcher Robert Gaunt chose him to participate in a groundbreaking series of operations.
Gaunt and his colleagues had been working for years on developing brain implants that let disabled patients control prosthetic limbs with their thoughts. “Slowly but surely, we have been moving this research forward,” study co-author Michael Boninger, a professor at Pitt as well as the director of post-acute care for UPMC’s Health Services Division, said in a news release.
This experiment moved the team’s efforts in a new direction. Four arrays of microelectrodes were implanted into the region of Copeland’s brain that would typically take in sensory signals from his fingers. Over the course of several months, researchers stimulated specific points in the somatosensory cortex, and mapped which points made Copeland feel as if a phantom finger was being touched.
“Sometimes it feels electrical, and sometimes it’s pressure,” Copeland said, “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.’
To test the results, the researchers placed sensors onto each of the fingers of a robotic hand. They connected the system to Copeland’s brain electrodes, and put a blindfold over his eyes. Then an experimenter touched the robo-hand’s fingers and asked Copeland if he could tell where the feeling was coming from.
Over the course of 13 sessions, each involving hundreds of finger touches, Copeland’s success rate was 84 percent. The index and little fingers were easy to identify, while the middle and ring fingers were harder.
During the experiment, Copeland learned to distinguish the intensity of the touch to some extent – but for what it’s worth, he couldn’t distinguish between hot and cold. That’ll have to come later.
“The ultimate goal is to create a system which moves and feels just like a natural arm would,” Gaunt said. “We have a long way to go to get there, but this is a great start.”
Prabhakar said neurotechnology is a high priority for DARPA, in part because of the kinds of injuries that warfighters have suffered in conflicts abroad.
“Lower-limb prosthetics have gotten very good – but upper-limb prosthetics, until very recently, have still been limited to a very simple hook,” she said.
One of the advanced robotic arm models funded by DARPA is just now hitting the commercial market. It’s called the Luke Arm, in honor of the prosthetic that was given to Luke Skywalker in “Star Wars.”
The experiments in Pittsburgh add touch sensitivity to the mix. and there’s more to come. Prabhakhar shared a video clip in which a patient who lost most of his arm could feel the touch of a virtual hand upon a computer-generated door.
“Oh my God! I just felt that door,” the patient said. “God, that is so cool.” (You can watch the clip starting at the 28:30 mark in the archived GeekWire Summit video.)
Prabhakar said the system was wired into the nerves running from what was left of the patient’s arm.
“We don’t have to go into his brain directly,” she explained. “That chip is just in the peripheral nervous system. We now know how to send the precise neural signals that give him a sensation of touching that virtual door.”
Prabhakar said that kind of technology can be applied to much more than rehabilitation. Human-computer interfaces that blend the real world with virtual reality, including virtual touch, could open the door to enhancing human experience and connecting us with the outside world in completely new ways.
“We don’t know where all that’s going to go yet,” she said. “But it’s an interesting threshold.”