The experiment involved two moneys, a male and a female, with electrodes attached to their brains to record neural activity.
The task was to control to virtual arms on a computer monitor by placing both hands over circular and square objects. The monkeys were rewarded with fruit juice if their avatars held the shapes for 100 milliseconds.
"No device will ever work for people unless it restores bimanual behaviors,” says neuroscientist Miguel Nicolelis at Duke University, North Carolina. "You need to use both arms and hands for the simplest tasks.”
The female monkey was trained to use joysticks to move virtual arms. After a year of practicing this way she was strapped in a chair and asked to repeat the task. After weeks of practice she was able to move the virtual hands 75 percent of the time.
While the technology used to extract the neural signals from all the other brain signals isn't new, Jose Contreras-Vidal, a biomedical engineer at the University of Houston, says the real achievement is finding the neurons that needed to be recorded to control the two arms.
In 2011, Nicolelis made a bold claim on "The Daily Show" that he was developing a robotic, thought-controlled "exoskeleton." He said the body suit will enable a paralyzed person to kick a soccer ball during the opening ceremony of the world cup in Brazil in 2014.
The brain controls all movement and can send signals even if a damaged limb is amputated. Brain-machine interfaces can pick up these signals and translate them to produce movement in a real or virtual prosthetic. So far BMIs have been successful in moving one body part at a time, but not two parts simultaneously.