Jan Scheuermann knew what she wanted to do if and when she mastered the robotic arm. The 53-year-old woman, paralyzed from the neck down, was going to have some chocolate.

And she did.

Tiny electrodes implanted in her brain picked up her wishes and made the arm and hand move, researchers reported Monday in the Lancet medical journal.

Neurosurgeons have been working for years to identify individual brain cells associated with movement and thought. This is a new way of getting there, the researchers report in the Lancet medical journal.

“This is completely new territory. Every time you move, billions of neurons fire together,” said neurobiologist Dr. Andrew Schwartz of the University of Pittsburgh Medical Center, who worked on the study. “We are starting to learn what these neurons are saying to one another.”

Jan Scheuermann, who has quadriplegia, takes a bite out of a chocolate bar she has guided into her mouth with a thought-controlled robot arm. Research assistants Brian Wodlinger, Ph.D., and Dr. Elke Brown watch in the background.

The robotic arm is an advance for prosthetics controlled by the brain. “We are much more closely replicating natural arm and hand movement than has ever been done before,” Schwartz said. “We could actually decode the subject’s intention to move. That is very useful for prosthetics. There is no other way a subject can actually express intention to move.”

Since having the electrodes implanted, Scheuerman calls it "the ride of my life.”

“This is the roller coaster. This is skydiving. It’s just fabulous, and I’m enjoying every second of it," she says.

Scheuermann has a degenerative spinal disease and has been paralyzed for about nine years, Schwartz said. “She has a spinal cord degeneration so that her condition is very similar to someone that has suffered a spinal cord injury,” Schwartz said. “She can’t move anything below her neck.”

Schwartz and colleagues implanted two separate arrays with 96 electrodes in Scheuermann’s motor cortex, the part of the brain that initiates movement. Each one is about 1/16^th of an inch long, Schwartz said, a fairly simple procedure for brain surgeons.

Study participant Tim Hemmes (right) reaching out to his researcher, Wei Wang, M.D., Ph.D. (left), using a brain-controlled prosthetic arm. Also pictured: Research team member Jennifer L. Collinger, Ph.D and Katie Schaffer.

“You don’t feel it," Schwartz said. "There are a lot of patients undergoing procedures for Parkinson’s disease in which they implant electrodes in the middle of your brain to stimulate it order to relieve symptoms. It’s much more invasive than this and yet it’s routine.”

After the implant, Scheuermann's training started. The arm is mounted on a stand near Scheuerman’s wheelchair. She gradually learned to control the arm by thinking about what she wanted it to do. After 13 years, the brain circuits were still there, Schwartz said.

“The second day of the experiment, she was able to move the prosthetic,” Schwartz said. “I sort of expected that to happen. My colleagues were much more skeptical. We had a bet that she could do it the first day. I lost the bet, and ended up buying ice cream for everybody.”

Scheuermann learned to pick up a rock, stack cones and eventually fed herself a candy bar. You can see video of the arm here.

“What we want to do sometime in the near future is mount the arm in her wheelchair so she can take it around with her and use it in her house,” Schwartz said.

Several other teams of researchers were working on mind-controlled prosthetics, but this one uses different computer programs, says Schwartz. The whole project is funded by the Defense Advanced Research Projects Agency, or DARPA. The device cost several hundred thousand dollars but with more production the price would come down, Schwartz says.

“This prosthetic arm was developed with the returning war veterans in mind,” he said. But amputees won’t be getting brain implants any time soon, he said, because doctors and the Food and Drug Administration won’t approve surgery that could further injure people who have already lost limbs.

For now, amputees may have to make do with prosthetics powered by muscle movements.

One downside: After about a year, the brain begins to build scar tissue around the implants and the signal starts to die out. Schwartz says his team is working on making implants with materials the brain won’t reject as foreign.

“This bioinspired brain-machine interface is a remarkable technological and biomedical achievement. Though plenty of challenges lie ahead, these sorts of systems are rapidly approaching the point of clinical fruition,” Grégoire Courtine of the Swiss Federal Institute of Technology in Lausanne and colleagues wrote in a commentary on the study.

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• Double amputee uses thought-controlled arm
• Will human minds control artificial limbs?