US researchers have developed a technology that allows monkeys to move a computer cursor with their minds alone -- raising the possibility that a similar system could one day help people with severe paralysis communicate and function more independently.

This stranger-than-fiction science, in which implanted electrodes helped the monkeys' brain activity control the computer-cursor movement, could potentially be applicable to humans.

However, these findings only suggest such mind-controlled machines are feasible, and any actual use of this technology is a long way off.

The investigators first studied the brain's electrical activity in three monkeys with electrode implants as they moved the computer cursors with a hand-controlled device. Certain nerve cells, or neurons, fire as the hand moves through space, and the researchers were able to create a mathematical model that related the firing of neurons to the cursor's position.

They found that the activity in just a handful of neurons in the brain's motor cortex could be "decoded" into a signal capable of moving the computer cursor via thin cables that connect the implant to the computer.

In the experiments, the monkeys played a simple game in which they moved the computer cursor to target positions on the screen. At certain points the hand-control device was turned off so that, even though the animals continued to move their hands, their corresponding brain activity was actually moving the cursor.

A similar implant device, coupled with computer technology, could in the future allow the severely paralyzed to perform functions as basic to everyday life as turning lights on and off and communicating through e-mail. It might even be possible for patients to control robotic limbs that perform complex movements such as writing.

Nature March 14, 2002;416:141-142