People are already using a range of devices which involve connecting the brain to a computer. One well-known device is the cochlear implant - a device like a miniature microphone that transmits sound signals directly to the brain and enables deaf people to hear.

A completely new application now enables those who have lost an arm or a leg to control their artifical limb by thought alone. The first patient to try out the new technology is Matt Nagel. Matt was left paralysed from the neck down after a vicious knife attack four years ago.

In the operating theatre a circular piece of his skull was removed and a tiny plate with 96 hair-thin electrodes was placed on the surface of Matt's brain. This will detect the electrical signals in the part of the brain that usually controls hand movement. A thin cable emerges from the skin on his head and runs to a small computer which decodes the signals and converts them into commands controlling an artificial hand connected to Matt's arm.

Shortly after the operation Matt is surrounded by the surgeons as he stares at the open hand, thinking "Close, close". To their delight the hand moves and the fingers close, becoming a fist. In that moment Matt Nagel makes history. He is the first person to have controlled an artificial limb using a device surgically implanted into the brain.

Since the operation Nagel has been test-driving the technology, seeing what he, and it, are capable of. "We're evaluating his ability to do a whole range of things. We've hooked him to a computer that lets him turn a TV on and off, change channel and adjust the volume just by thinking," says the scientist leading the project.