MONDAY, Oct. 13, 2003 (HealthDayNews) -- Monkey see, monkey make robot arm do.
Duke University Medical Center researchers have taught rhesus monkeys to use brain signals and visual feedback from a video screen to control the movement of a robotic arm. The monkeys learned to manipulate the robot arm as if it were actually their own limb.
This research could help in the development of technology that would enable paralyzed people to use their brain signals to control mechanical artificial limbs or even send commands to free roaming helper "neurorobots."
The researchers also say the technology they developed to analyze the monkey's brain signals could be a step towards improving the rehabilitation of people who suffer brain or spinal cord damage from stroke, trauma or disease.
In this study, published online Monday in the first issue of the Public Library of Science, the Duke scientists implanted an array of electrodes in areas of the two monkeys' brains that produce commands to control complex muscle movement.
The electrodes collected the brain signals, which were then analyzed by a computer system the scientists developed to recognize patterns of signals that represented particular movements by the monkeys' arms.
Initially, the monkeys were taught to use a joystick to position a cursor over a target on a video screen and to grasp the joystick with a specified force. As the monkeys did this, their brain signals were recorded and analyzed.
The monkeys then learned to use the joystick/cursor combination to control a robotic arm. After the joystick was removed, the monkeys moved their arms to manipulate and "grab" the cursor and control the robot arm.
"The most amazing result, though, was that after only a few days of playing with the robot in this way, the monkey suddenly realized that she didn't need to move her arm at all," lead researcher Dr. Miguel Nicolelis, a professor of neurobiology and co-director of the Duke Center for Neuroengineering, says in a prepared statement.
"Her arm muscles went completely quiet, she kept the arm at her side and she controlled the robot arm using only her brain and visual feedback. Our analyses of the brain signals showed that the animal learned to assimilate the robot arm into her brain as if it was her own arm," Nicolelis says.
He notes that both reaching and grasping tasks were controlled from the same sets of implanted electrodes.
"We knew that the neurons from which we were recording could encode different kinds of information. But what was surprise is that the animal can learn to time the activity of the neurons to basically control different types of parameters sequentially," Nicolelis says.
"For example, after using a group of neurons to move the robot to a certain point, these same cells would then produce the force output that the animals need to hold an object. None of us had ever encountered an ability like that," he says.
In another important finding, analysis of the monkeys' brain signals as they learned to control the robotic arm with their thoughts revealed that their brain circuitry was actively reorganizing itself to adapt.
"It was extraordinary to see that when we switched the animal from joystick control to brain control, the physiological properties of the brain cells changed immediately. And when we switched the animal back to joystick control the very next day, the properties changed again," Nicolelis says.
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