From Scientific American:
Eight years ago, when Erik Ramsey was 16, a car accident triggered a brain stem stroke that left him paralyzed. Though fully conscious, Ramsey was completely paralyzed, essentially “locked in,” unable to move or talk. He could communicate only by moving his eyes up or down, thereby answering questions with a yes or a no. Ramsey’s doctors recommended sending him to a nursing facility. Instead his parents brought him home. In 2004 they met neurologist Philip R. Kennedy, chief scientist at Neural Signals in Duluth, Ga. He offered Ramsey the chance to take part in an unusual experiment. Surgeons would implant a high-tech device called a neural prosthesis into Ramsey’s brain, enabling him to communicate his thoughts to a computer that would translate them into spoken words.
Today Ramsey sports a small metal electrode in his brain. Its thin wires penetrate a fraction of an inch into his motor cortex, the part of the brain that controls movement, including the motion of his vocal muscles. When Ramsey thinks of saying a sound, the implant captures the electrical firing of nearby neurons and transmits their impulses to a computer, which decodes them and produces the sounds. So far Ramsey can only say a few simple vowels, but Kennedy believes that he will recover his full range of speech by 2010.
Ramsey’s neural prosthesis ranks among the most sophisticated implanted devices that translate thoughts into actions. Such systems listen to the brain’s instructions for movement—even when actual movement is no longer possible—and decode the signals for use in operating a computer or moving a robot.