Monkeys Control a Robot Arm With Their Thoughts

By BENEDICT CAREY

Published: May 29, 2008

Two monkeys with tiny sensors in their brains have learned to control a prosthetic arm with only their thoughts, using it to reach for and grab food and even to adjust for the size and stickiness of morsels when necessary, scientists reported Wednesday.

The report, released online by the journal Nature, is the most striking demonstration to date of brain-machine interface technology, which scientists expect will eventually allow people with spinal cord injuries and other paralyzing conditions to gain more control over their lives. The findings suggest that brain-controlled prosthetics, while not yet practical, are at least technically within reach.

In previous studies, researchers showed that humans who had been paralyzed for years could learn to control a cursor on a computer screen with their brain waves; and that thoughts could move a mechanical arm, and even a robot on a treadmill.

Yet the new experiment demonstrates how quickly the brain can adopt a mechanical appendage as its own, refining movement as it interacts with real objects in real time. The monkeys in the experiment had their own arms gently restrained while they were learning to use the prosthetic one.

“In the real world things don’t work as expected, the marshmallow sticks to your hand or the food slips, and you can’t program a computer to anticipate all of that,” said the paper’s senior author, Dr. Andrew Schwartz, a professor of neurobiology at the University of Pittsburgh. “But the monkeys’ brains adjusted; they were licking the marshmallow off the prosthetic gripper, pushing food into their mouth, as if it were their own hand.”

Dr. John P. Donoghue, director of the Institute of Brain Science at Brown University, said that the new report “is important because it’s the most comprehensive study showing how an animal interacts with complex objects, using only brain activity.” Dr. Donoghue was not involved in the research.

Such systems, Dr. Kalaska wrote, “would allow patients with severe motor deficits to interact and communicate with the world not only by the moment-to-moment control of the motion of robotic devices, but also in a more natural and intuitive manner that reflects their overall goals, needs and preferences.”

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