Brain implants let paralyzed man move robotic arm

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A paralyzed man can now make a robotic arm do some smooth moves. Tiny silicon chips embedded in an action-planning part of his brain let the man control the arm easily and fluidly with his thoughts, scientists report in the May 22 Science.

“This is groundbreaking,” says neural engineer Bradley Greger of Arizona State University in Tempe. “It’s going into a new area of the brain and tapping into high-level thoughts.”  

Researchers have previously tapped into the motor cortex, the brain region that tells muscles to move, to steer thought-controlled robotic limbs (SN: 6/16/12, p. 5). But years of researching a different region, the posterior parietal cortex, or PPC, convinced Caltech neuroscientist Richard Andersen to try something new.

The PPC, a strip of tissue about the size of a small cellphone, lies in the crumpled, outer sheet of the brain and helps plan out movements. “It occurred to us that this area would be an ideal source of control for prosthetics,” Andersen says.

So his team implanted two chips — each smaller than an eraser tip and carpeted with spikes, like little beds of nails — into the PPC of Erik Sorto, who is quadriplegic. The spikes nestle among his nerve cells and record the neural chatter that makes up Sorto’s thoughts. A computer then decodes the chatter and tells a robotic arm how to turn Sorto’s thoughts into actions.

With this device, Sorto was able to pick up a beer and bring it smoothly to his lips. The action looks effortless because he has to think only about what he wants to do — the machine figures out how to do it.

That’s how natural movement works, Greger says. “If I reach out to pick up my cellphone, I don’t have to think: Flex my elbow, extend my hand, open my fingers, close my fingers,” he says. “I just think, ‘I want my phone.’”