Researchers in Japan and the United States said Wednesday they have learned to use the brain activity of monkeys to control the walking motion of a robot halfway across the world.

The experiment is part of work to develop prosthetic limbs people with disabilities might one day be able to control mentally, said neurologist Miguel Nicolelis from Duke University in North Carolina.

"What we are showing here is that we can harvest the signals and send them to a device that can restore mobility," said Nicolelis in a statement.

Duke researchers attached electrodes to one of two rhesus monkeys to monitor their brain activities, recording the brain cell responses as the monkey walked on a treadmill at various speeds while simultaneously sensors on the monkey's legs tracked the movements.

These brain signals were sent to a 1.55-metre-tall robot in a laboratory in Kyoto run by the Computational Brain Project of the Japan Science and Technology. As the monkey walked, so, too, did the robot, which was receiving signals sent through wires attached to its legs.

"Not only could the monkey control both his legs and the legs of the robot at the same time but when we stopped the treadmill here at Duke and the monkey stopped walking, using the visual feedback she was getting from Japan she was still able to sustain the locomotion of the robot for a few minutes just by thinking," said Nicolelis.

The Japanese agency and Carnegie Mellon University in Pittsburgh designed the robot to move in response to brain signals.

The results are the latest advance in the research at the Duke University Medical Center. In 2003, Nicolelis and his colleagues ran an experiment in which they taught monkeys to use their thoughts to move a robotic arm. Those results were published in online journal PLoS Biology, published by the Public Library of Science.