Monkeys Adapt Robot Arm as Their Own

Robo-Monkey is coming!

Monkeys that learn to use their brain signals to control a robotic arm are not just learning to manipulate an external device, Duke University Medical Center neurobiologists have found. Rather, their brain structures are adapting to treat the arm as if it were their own appendage.

The finding has profound implications both for understanding the extraordinary adaptability of the primate brain and for the potential clinical success of brain-operated devices to give the handicapped the ability to control their environment, said the researchers.
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In the study, Lebedev performed detailed analysis of the mass of neural data that emerged from experiments reported in 2003, in which the researchers discovered for the first time that monkeys were able to control a robot arm with only their brain signals.

In those experiments, the researchers first implanted an array of microelectrodes -- each thinner than a human hair -- into the frontal and parietal lobes of the brains of two female rhesus macaque monkeys. The faint signals from the electrode arrays were detected and analyzed by the computer system the researchers developed to recognize patterns of signals that represented particular movements by an animal's arm.

In the initial behavioral experiments, the researchers recorded and analyzed the output signals from the monkeys' brains as the animals were taught to use a joystick to both position a cursor over a target on a video screen and to grasp the joystick with a specified force.

After the animals' initial training, however, the researchers made the cursor more than a simple display. They incorporated into its movement the dynamics, such as inertia and momentum, of a robot arm functioning in another room. While the animals' performance initially declined when the robot arm was included in the feedback loop, they quickly learned to allow for these dynamics and became proficient in manipulating the robot-reflecting cursor, found the scientists.

The scientists next removed the joystick, after which the monkeys continued to move their arms in mid-air to manipulate and "grab" the cursor, thus controlling the robot arm. However, after a few days, the monkeys realized that they did not need to move their own arms. Their arm muscles went completely quiet, they kept the arm at their side, and they controlled the robot using only their brain and visual feedback.