Spinal cord work-around reanimates paralyzed hand

With the help of a neural prosthesis, a quadriplegic man used his paralyzed right hand to grab a bottle, swipe a credit card and play a guitar video game. Bypassing his damaged spinal cord, the system restored his ability to use his thoughts to command his hand to move.  

Other neural prosthetic systems have allowed paralyzed people to use their brain activity to move computer cursors, robotic limbs and wheelchairs (SN: 11/16/13, p. 22). But the new approach, described online April 13 in Nature, is the first to use brain activity to control a person’s own limb. “We literally are reconnecting the brain to the body,” study coauthor Chad Bouton of the Feinstein Institute for Medical Research in Manhasset, N.Y., said April 12 in a news briefing. 

Decoding brain signals and correctly stimulating muscles are “really hard things to do individually,” says biomedical engineer Levi Hargrove of the Rehabilitation Institute of Chicago. Putting those together in a human subject is “very impressive,” he says. “There’s more work to be done, of course, but this is very positive and should excite people.”

In 2010, college student Ian Burkhart dived into a shallow wave and struck sand. The accident severed his spinal cord, leaving him paralyzed from the shoulders down. Burkhart volunteered to undergo brain surgery in which doctors implanted a patch of electrodes directly into his brain. These electrodes eavesdropped on the activity of nerve cells that control hand movements.

Scientists listened to these cells’ behavior as Burkhart watched a range of hand and finger movements on a screen and attempted to copy the motions. A computer system then learned to recognize the neural signals that accompanied each type of movement, and an algorithm translated those signals into movement commands. 

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A flexible sleeve of electrodes strapped to Burkhart’s forearm delivered those instructions directly by stimulating hand muscles. In 2014, Bouton and colleagues announced that Burkhart could open and close his hand using the system. Since then, Burkhart has been able to command more complex hand movements, such as wiggling his thumb in and out and flexing his wrist. The Nature paper describes how this bypass system now allows him to pick up a cup, pour and even pinch his thumb and forefinger together to pluck a skinny stir stick.

“The first time when I was able to open and close my hand, it really kind of gave me that sense of hope again for the future,” Burkhart said in the briefing.

The technology isn’t ready for life outside of the lab. In its current form, the system must be calibrated each time Burkhart uses it, and the electrodes in the brain may not perform as well with time. And bulky cables connect the brain electrodes to the computer system and forearm sleeve. Scientists are working on making the technology smaller, wireless and easier to use, study coauthor Nick Annetta of Battelle Memorial Institute in Columbus, Ohio, said in the briefing.

Neural engineer José Contreras-Vidal of the University of Houston points out that technology that can translate neural activity into electrical impulses may ultimately restore other types of muscle activity, such as walking. “What we need to do is provide solutions and options,” he says.