Ian Burkhart was 19 years old when he broke his neck diving into shallow water on holiday. Since then, he has been unable to move either of his legs, or his arms below the elbow. Now, in a world first, he has regained control of one hand and his fingers using a mind-reading device. In the past few years, we have seen paralysed people walk again with the aid of exoskeletons, and by using recorded brain activity to trigger electric stimulations to the leg muscles. Others have trained paralysed people to control computer cursors and robotic limbs by thought alone.
But what quadriplegic people really want is to regain control of their hands, says Ali Rezai at Ohio State University.
So Rezai and Chad Bouton of the Feinstein Institute in Manhasset, New York, and colleagues, implanted a pea-sized array of 100 electrodes in the part of Burkhart’s brain responsible for controlling movement. The team found the area by scanning Burkhart’s brain before surgery while he thought about moving his limbs. They pinpointed the part responsible for his right hand by electrically stimulating it during the surgery, and watching to see if that hand twitched.
The group also developed a sleeve of electrodes to jolt Burkhart’s arm muscles into action. The electrodes stimulate muscles that control specific hand and finger movements, such as pinching and grasping.
Burkhart started a training programme to learn to control the sleeve with his thoughts.
First, he watched a virtual hand clench and release, which encouraged him to think about making the same movements.
Recordings of his brain activity were fed to a computer, which translated them using an algorithm, and sent a signal to control the electrode sleeve. It took a while for him to get the hang of the device, and for the computer to learn how to decode his thoughts. “But with repetition, the signal becomes clearer over time,” says Rezai. “The software learns to make the movements smoother and faster.”
Practice makes perfect
Burkhart has been practising for 4 hours a day, two or three times a week, for the last couple of years. Now he can open and close his hand, pick up a bottle and pour out its contents, and use a stick to stir the contents of a mug, for example. He has even been able to use the device to play the Guitar Hero video game.
“Initially, Ian could just about clench his hand [using the device], but now he can perform individual finger grasps with about 70 per cent accuracy,” says Rezai. “And he’s getting better.”
Lee Miller at Northwestern University, who enabled monkeys to control robotic limbs with their thoughts, reckons that the team could improve accuracy if they stimulated Burkhart’s muscles internally, rather than using an external sleeve of electrodes.
But Rezai and his colleagues want to make the system as non-invasive as possible. Eventually, Rezai hopes to be able to implant brain sensors without surgery, perhaps by injecting sensors beneath the scalp. The researchers also have plans to develop external electrodes to control other limbs, and perhaps weave these devices into clothing.
Even if that were the case, a paralysed person would probably still need help in applying the electrodes every day, points out David Guiraud of the Montpellier Laboratory of Computer Science, Robotics and Microelectronics in France. “It is a nice piece of technology that broadens the possibilities for quadriplegics, but we are still far from a widespread application and concurrent approaches should continue to be considered,” he says.
In the meantime, Rezai and his colleagues hope Burkhart can eventually learn to use the sleeve to perform a wider range of functions. The group also have plans to use the system in other people paralysed after a spinal cord injury or stroke.
Journal reference: Nature, DOI: 10.1038/nature17435