Matt Nagle loves surfing TV channels, playing computer games and reading e-mails. But unlike his friends, the 25-year-old paraplegic controls all these devices purely by the power of thought. Mind control used to be the exclusive domain of science fiction. Now Mr Nagle, whose spinal cord was severed in a stabbing attack five years ago, provides living proof that wild imagination is destined to become reality. In 2004, doctors implanted a silicon chip the size of a baby aspirin in the part of his brain responsible for movement. Attached to the surface of the motor cortex, the chip has 100 electrodes, each thinner than a human hair, that detect brain activity - and intentions. When he thinks 'move left' or 'move right' his mouse cursor responds accordingly. 'It was kind of a trip that my brain signals were controlling a mouse, changing channels on my TV, adjusting the volume and opening e-mails,' he says. 'Maybe in a couple of years we can start moving our limbs.' Mr Nagle is the public face of pioneering research that is beginning to unlock the mysteries of the brain, which has long been considered the final frontier of medical science. Stunning technological advances mean that scenarios popularised in Hollywood sci-fi flicks no longer seem quite so wacky. And it's the exploding area of research on devices far smaller than can be seen by the naked eye that is offering most hope. It's this kind of nanotechnology that allowed US scientists to begin the trial on patients like Mr Nagle. Their technology harnesses the minute electrical signals that a brain uses to communicate. In movement, an electrical pulse from a cluster of neurons passes through a string of other neurons, eventually sparking a muscle into action. But a team in Massachusetts found those signals - which persist in the brain long after a spinal cord injury - could be recorded and routed outside the brain and decoded by a computer into command signals. Scientists at Brown University on Rhode Island are now attempting to develop a wireless version of the BrainGate technology, which would eliminate the need to be directly connected to a computer. 'The electrodes only need to come close to neurons to pick up their signals,' said Professor John Donoghue, the programme's director. 'A device that transmits the signals from a small capsule inside the body will send signals wirelessly through the skin using infrared light similar to a TV remote control.' Some experts believe BrainGate is merely the first step. They say able-bodied people will be able to use everyday items from computers to mobile phones and household items purely by the power of the mind. And they hope the BrainGate concept will become sophisticated enough to transmit signals directly to the body's muscles, allowing paralysed people full use of their limbs. But if these bionic man scenarios seem far fetched, they pale in comparison to the predictions of some futurists who claim inevitable advances in our understanding of the brain will make the Renaissance and Enlightenment seem like minor staging posts in human history. They say today's increasingly sophisticated MRI scanning technology will be replaced by 'nanobots', or powerful, microscopic scanners. Millions could be sent into the bloodstream to map every capillary of the brain. And they could be attached to key parts of the brain, communicating with each other wirelessly or to outside machines. That may be a startling concept, but brain researchers like Ashley Craig are convinced it will remain in the realms of fantasy. In the mid-1990s his team at Sydney's University of Technology developed Mind Switch, a precursor to BrainGate that had similar 'thought control' goals but used sensors attached to the head rather than an implant. 'I think the way to go forward is probably not inside the brain,' says Professor Craig, who says the implants are invasive, costly and risky. 'Even in 50 or 100 years, unless the science progresses beyond our wildest dreams, I don't think I would be willing to open up my skull for whatever reason.' Four years ago Professor Craig led the world's first human trial on 'brain computer interface (BCI)' technology, and successfully showed 10 severely disabled people turning on a TV and changing channels simply by thinking about it. His work is now focusing on understanding the effects of stress and fatigue, and he predicts ways of controlling certain feelings or personality traits may soon be found. But while his work is focused on improving people's lives, he accepts that brain manipulation also appeals to those with 'darker' motives. 'I think this research opens up issues I would have less enthusiasm for,' he says. Researchers in New York recently developed remote-controlled rats, known as 'Roborats', that were guided through mazes by joystick. Reports in Japan told of experiments in which volunteers wearing a headset were moved left or right by the flick of an external joystick. Ethicists warn of chilling implications arising from technology that could alter and suppress neural signals, or ultimately control the mind. After developing Mind Switch, Professor Craig was approached by American companies who wanted to operate missile systems by thought control. 'We were reluctant to go down that path,' he says. 'We did not want Mind Switch used for those sorts of purposes. We developed it for non-aggressive applications. But we can't stop other people around the world and I'm sure there will be people doing things that we didn't want to.'