Monkey business leads to hope of brain-powered prosthetics

USING only its brainpower, a monkey can direct a robotic arm to pluck a marshmallow from a skewer and stuff it into its mouth, researchers have said.

“They are using a motorised prosthetic arm to reach out, grab and bring the food back to their face,” said Andrew Schwartz of the University of Pittsburgh School of Medicine, whose study will appear in the journal Nature.

Schwartz said the technology may lead to brain-powered prosthetic limbs for people with spinal cord injuries or disabling diseases.

Until now, such brain-machine interfaces have been used to control cursor movements on a computer screen. Schwartz and colleagues wanted to apply the technology to real-world tasks.

The monkey guides the robot arm the same way it does its natural limbs, through brain signals.

Schwartz’s team picks up those signals through an array of microelectrodes implanted in the monkey’s brain. These signals are relayed to a computer that operates the robotic arm.

Schwartz said his team has learned certain motor neurons fire rapidly when the monkey wants to move a certain way. “Each neuron seems to have a preferred direction,” he said.

“One cell will fire a lot if you move upward. Another cell will fire a lot if you move to the right. All you really need to do is listen to these neurons at the same time to determine which direction the animal wants to move in.

“We record those patterns of action potential, interpret them with a computer and extract the monkey’s intention to move. That serves as a control signal to the robot,” he said.

Schwartz said it takes about three days for a monkey to learn to operate the arm.

So far, they have trained two monkeys to feed themselves with the robotic arm.

The goal is to develop a brain-powered prosthesis that can restore near-natural function to an amputee or person with a spinal cord injury.

The next step is to develop an operating wrist and jointed fingers to add dexterity to the device.

“If you look at what these patients really need, they need to be able to use their fingers to increase their quality of life. They need to button shirts and pull zippers and things like that,” Schwartz said.


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