It's all possible because of technology that intercepts and decodes electrical signals from the brain before they reach Burkhart's damaged spine.
"We're actually routing them around the spinal cord injury and then reinserting those signals into the muscles," says Chad Bouton, the study's first author and vice president of advanced engineering at the Feinstein Institute for Medical Research in Manhasset, N.Y.
The system relies on electrodes implanted in Burkhart's brain, a computer interface attached to his skull, and electrical stimulators wrapped around his forearm. It was developed by a team at Ohio State University and Battelle Memorial Institute, in Columbus, Ohio, where Bouton used to work.
At first, Burkhart could grasp objects, but he would drop them when he moved his arm. His skill has improved steadily, though, Bouton says.
"Ian is learning how to think about very detailed movements and the machine is actually learning how to decipher those signals more effectively as well," Bouton says. "So they're actually learning together."
Burkhart's achievements have received a great deal of media attention. But he is just one of many paralyzed people using technology that allows them to perform daily tasks using their thoughts.
And much of the technology Burkhart relies on is also in use at other research centers, says Robert Kirsch, chairman of the department of biomedical engineering at Case Western Reserve University and executive director of the Cleveland Functional Electrical Stimulation Center.
"The brain computer interfacing that they did is kind of garden variety," Kirsch says. "And the electrical stimulation that they've done is really old-fashioned."
Other groups have obtained better results using electrical stimulators that are implanted in muscles, instead of placed on the skin, Kirsch says. That approach requires extra surgery but allows more precise control of muscles, he says.
At a scientific meeting last year, a member of Kirsch's team reported on a person using their technology who is able to use thoughts to trigger muscles in both the arm and hand. That's important, Kirsch says, because, unlike Burkhart, many other paralyzed people have no use of their arms or shoulders.
More than a decade of experiments has shown that paralyzed people can learn to use their thoughts to control computers, robotic arms and even their own limbs, says Leigh Hochberg, a professor of engineering at Brown University. Unfortunately, the systems that make this possible still aren't suitable for use at home, he says.
What people who are paralyzed really want, Hochberg says, is "a fully implanted technology, one that doesn't have wires or plugs that are sticking up above the scalp, doesn't have wires that are wrapped around the outside of the arm."
And that, he says, will require technological advances — including the ability to transmit signals from the brain without using wires.
"The process of getting from where we are today, which is some exciting early clinical research, all the way through to a clinically useful, vetted device that will help someone with paralysis is still a long one," Hochberg says.