Monkeys Control Robot Arm with Brain Signals

The achievement is an important step toward improving the rehabilitation of people with brain and spinal cord damage from stroke, trauma, or disease.

The researchers first implanted an array of microelectrodes, each smaller than the diameter of a human hair, into the frontal and parietal lobes of the brains of two female rhesus macaque monkeys. They chose frontal and parietal areas because they are known to be involved in producing multiple output commands to control complex muscle movement. The faint signals from the electrode arrays were detected and analyzed by a computer system developed to recognize patterns of signals that represented particular movements by an animal's arm.

After initially training the monkeys on a joystick to position a cursor over a target on a video screen and to grasp the joystick with force, the researchers incorporated into the cursor's movement the inertia and momentum of a robot arm functioning in another room. The monkeys quickly learned to allow for these dynamics and became proficient in manipulating the robot-reflecting cursor. Then the researchers removed the joystick, after which the monkeys continued to move their arms in mid-air to manipulate and "grab” the cursor, thereby controlling 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 she didn't need to move her arm at all,” said Miguel Nicolelis, M.D., professor of neurobiology at the Duke Medical Center for Neuroengineering (Durham, NC, USA), who led the study. "Her arm muscles went completely quiet, she kept her arm at her side and she controlled the robot arm using only her brain and visual feedback.”

As the animals learned, an analysis of their brain signals revealed that the brain circuitry was actively reorganizing itself to adapt. When the animals were switched back to the joystick control, the properties changed again. The researchers are already conducting studies of human subjects, performing analysis of brain signals to determine whether they correlate with those seen in the animal models. They are also exploring techniques to increase the longevity of the electrodes beyond the two years they have currently achieved in animals studies.

An article on this research, co-authored by Dr. Nicolelis, was reported online October 13, 2003, in PloS Biology, the recently launched Public Library of Science journal that provides full, free online access to the results of scientific and medical research.




Related Links:
Duke Medical Center for Neuroengineering
PloS Biology