Nicolelis took advantage of a series of brain surgeries performed on 11 patients with Parkinson's disease, an incurable disease marked by the destruction of certain brain cells. These operations are routinely performed with the use of deep brain stimulators to help counteract the tremors associated with Parkinson's disease. Nicolelis made the most of these opportunities by adding a simple manual task: the patients were asked to play a video game during the operation.

To find the best place to put the stimulators, surgeons implanted temporary arrays of microelectrodes. The patients were awake during surgery so they could guide the surgeon. As the patients played the game, the electrodes sent their brain signals to a computer, which analyzed the signals and matched them with the hand movements used during the video games. The signals were then compiled into a neuronal model that could predict the signals needed to perform the actions required by the game.

While the monkeys had wires implanted in their skulls that were connected to an external device, Nicolelis' team has designed a wireless electrode array that could be implanted permanently. Some obvious applications of such technology would be a thought-controlled robotic arm, electric wheelchair, TV, or computer — or a prosthesis.

Dr. Josy Millyn at the Dalle Molle Institute in Switzerland has come up with a similar system. Instead of surgical implants, however, a cap studded with electrodes monitors brain activity through the scalp. Early trials using a steerable robot indicate that it is as easy to control the robot by thought as it is manually.