U.S. researchers say they have taught monkeys to play computer games using only their thoughts.

In an experiment at Duke University Medical Center in North Carolina, two monkeys learned to use a joystick, which was connected to a robotic arm, to move a cursor on a computer screen.

The robotic arm was kept in a separate room to avoid distraction. The animals could watch a monitor to see when they missed their target.

Courtesy: Duke News Service

The researchers later switched off the robotic arm, but their subjects continued to manipulate the joystick.

In time, one of the monkeys realized it didn't have to move its own arm to continue the game, because now the robotic arm was being controlled directly by signals coming from brain implants.

The other animal also stopped using the joystick.

The work was reported Monday in the first edition of the online journal PLoS Biology, published by the Public Library of Science.

Dr. Miguel Nicolelis and his colleagues said they watched as one of the monkeys continued the brain-powered game for almost an hour.

Before the laboratory experiment began, electrodes were attached to the animals' brains. One monkey got 96 electrodes in the frontal and parietal lobes, known to be the source of commands for muscular movement. The second monkey got 320 implants.

During the first stage of the experiment, researchers mapped the bioelectrical activity in the animals' brains and recorded patterns for each movement.

The researchers hope their findings will one day help people with spinal cord injuries to perform similar tasks.

Humans have already been implanted with a similar device that allows them to control the movement of a cursor on a computer screen through their thoughts. The implant used in the monkey work, however, is smaller and the task accomplished was more complex.