Brain-controlled arm could beat paralysis

A SIMPLE sip of coffee has brought closer the day when people who have been paralysed or lost limbs can look after themselves by controlling robots with their brain signals.

The coffee sip was taken by a 58-year-old woman paralysed in 1996 by a stroke. In the first test of its kind, she guided a flask of coffee to her lips using a robotic arm controlled by her brain.

"You could see an enormous grin when she managed it," says John Donoghue of Brown University in Providence, Rhode Island. "For the first time in 15 years, she was doing something for herself."

Previously, the team implanted a chip into the brain of a paraplegic man who then successfully used his neurological signals to manoeuvre cursors on computer screens. The latest experiment is the first in which humans have used their brain signals to manipulate real-world objects using a robotic arm. Similar results were achieved in monkeys in 2008.

"It's a big symbolic step forward," says Andrew Jackson of Newcastle University in the UK, who has an accompanying commentary in the same edition of Nature as the work (DOI: 10.1038/nature11076).

The woman and a 66-year-old man, who have both lost the use of their limbs, volunteered to have aspirin-sized arrays of electrodes implanted in their brains. These pick up signals from neurons in the motor cortex - the part of the brain that governs movement. Donoghue's Braingate2 team asked the two volunteers to watch a recording of the robotic arm perform programmed actions, and to imagine they were moving it themselves. By recording the brain signals corresponding to each arm movement, such as left, right, up or down, the computer could be "taught" to move the robotic arm as directed by brain signals from the patients.

In tests which required them to reach out for and grip a foam sphere the size of a tennis ball, one volunteer grasped the target in 62 per cent of attempts, and the other in 46 per cent of attempts. In a second test, performed only by the woman, she successfully gripped a flask of coffee and brought it to her lips for a sip from a straw in four out of six attempts.

Donoghue says the results are an important step towards assistive devices that can be controlled directly. "You can imagine an arm like this mounted on a wheelchair," he says.

A distant goal is to use the brain to reactivate a person's own muscles with the help of an implanted electrical device that reconnects the two within the body. Donoghue is working on such a system with a volunteer.

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