Researchers at Duke University showed that monkeys can control a robot arm with just thoughts and visual feedback. Miguel Nicolelis, codirector of the Center for Neuroengineering, Duke University Medical Center, and his colleagues implanted an array of microelectrodes into the frontal and parietal lobes of the brains of two female rhesus macaque monkeys. The researchers implanted 96 electrodes in one animal and 320 in the other, and recorded and analyzed output signals in the initial experiments from the monkeys' brains. They were taught to grasp a joystick with a specified force and use it to position a cursor over a target on a video screen.
After initial training, researchers complicated the activity by letting the animals control a robotic arm. The arm mimicked the movement of the monkeys' arms.
The scientists then removed the joystick. The monkeys continued to move their arms in mid-air as if working an imaginary joystick to manipulate and “grab” the cursor, thus controlling the robot arm.
“The most amazing result was that after only a few days of playing with the robot this way, the monkey suddenly realized she didn't need to move her arm at all,” says Nicolelis. “Her arm muscles went completely quiet, she kept the arm at her side and controlled the robot arm using only her brain and visual feedback. Our analysis of brain signals showed that the animal learned to assimilate the robot arm into her brain as if it was her own arm.”
“We know that the neurons from which we were recording could encode different kinds of information,” says Nicolelis. “But the surprise is that the animal learned to time the neuron activity to control different parameters. For example, after using a group of neurons to move the robot to a certain point, these same cells would produce the force output that the animal needed to hold an object. None of us had encountered an ability like that.”
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