Dr. Miguel Nicolelis, a neuroscientist at Duke University, achieved this remarkable feat by implanting microelectrodes into the brains of two rhesus monkeys, targeting the areas where nerve cells fire as the brain readies the body to move. Then he taught each monkey to play a specially designed video game. The animal grasps a joystick and learns to use it to "pick up" a cursor and drag it across a screen toward a target. When the cursor is successfully deposited on the target, the monkey gets a treat.
Meanwhile, the microelectrodes, monitoring the brain activity that goes with this game-playing, send impulses out through a series of wires and into another room, where they connect to a robotic arm. As the cursor moves, so does the arm. As the monkey squeezes, so does the robotic hand. The monkey thinks it's controlling the cursor with the joystick, but the animal's brain activity is actually doing the work. Only when the joystick is disconnected does the monkey realize that it can control the cursor without moving the stick. "It plays the game just by thinking," says Nicolelis. "And it takes only a few weeks to learn. We expected months."
This isn't the first time mechanical devices including prosthetic arms have been wired into a nervous system. But earlier experiments used peripheral nerves, not brain cells. "That technique," observes Nicolelis, "wouldn't help people with spinal-cord injuries or degenerative nerve disease."
The next step, he says, is to try this experiment with humans. Much of that work will be done over the next few years at a new institute in his native Brazil. Some is already under way, and, says Nicolelis, he hopes to publish preliminary results within a couple of months. It will still be a while before doctors attempt to wire full-fledged artificial arms and legs into the brains of the paralyzed. But for patients like Reeve, that goal now seems within reach.