Just by imagining their feet moving, patients using wheelchairs can again experience what it feels like to stroll down a high street, thanks to the work of British scientists who have found a new way of using the power of thought. They have devised the helmet which can link brain wave patterns to a virtual reality system, allowing the wearer to enter an illusory world of movement.

The new system has been tried out for the first time by an Austrian man who became a paraplegic after a swimming accident. Tom Schweiger was injured on holiday in Greece seven years ago when a huge wave swept him on to rocks, severing the spinal cord in his neck and leaving him paralysed apart from some movement in his left arm.

Last week 31-year-old Schweiger was able to enter a different virtual world when the scientists from his home country and a team at University College London tested the new system. When he was asked by researchers to think about moving either his foot or his hand, the changes in his brain waves - or electroencephalogram (EEG) signals - were recorded by electrodes on the top of his head. These were then turned into a control signal which was linked up to the virtual reality system.

Schweiger was given special 3D glasses to wear so that the images created in the 'virtual cave' created for the experiment, made up of a four-sided room complete with stereo sound and projected images, gave him the illusion of walking through a street. Different characters appeared on the screen and talked to him and he was asked to respond.

'I found it exciting, very exciting,' he said afterwards. 'At first it all felt strange, having the cap on and being asked to think about moving my feet, but gradually I felt as if I was in that world. At one point I completely forgot it was a virtual world and that I was part of this experiment. It was really interesting, and much more enjoyable than I expected.'

Mel Slater, professor of virtual environment at UCL, explained: 'Everyone's brain is different and we have unique EEG patterns, so you have to "train" the computer to recognise which movement corresponds to which patterns. For example, we know that foot movement is controlled by the EEGs that come from the top of the head. Every time you think about moving the foot, the same area of the brain is activated, whether or not you can actually move the foot.'

He added: 'What we have done is to develop software that can identify the different EEG signals, and tie it up to a virtual reality world. You can control this world purely by thought, and what we hope is that it will have really practical applications for the future. With this technology people are able to navigate through their environment, despite the nature of their disabilities.'

Slater believes that within five to 10 years it should be possible to develop the system further to enable people to control wheelchairs or move prosthetic arms simply by harnessing their thoughts. The system, known as the Brain-Computer Interface Project, was funded with £900,000 of UK government research money.

One aim is to help individuals with 'locked-in syndrome', where as a result of injury they maintain their brain function but lose all ability to move except for some movement in their eyes.

Dr Doron Friedman, a UCL computer scientist, said: 'We've been working on this for a number of years, but this is the first time we've been able to ask someone with a serious disability to use it, to see if he can immerse himself in this virtual reality environment.'

Friedman said that the biggest problem the scientists were facing was differentiating between EEG signals, so that they could be absolutely sure a particular one correlated to a particular movement by the disabled person involved. As people have many different thoughts simultaneously, the researchers need to know exactly which areas of the brain are being activated by which specific ones.

The ultimate goal is to give people such as Schweiger more freedom in their everyday lives, according to scientist Robert Leeb, of Graz University of Technology in Austria.

'If you are dependent on other people for absolutely everything, what you would most like is to regain some independence,' said Leeb.

'I would hope we could eventually use this process to be linked with a wheelchair, so its movements could be governed by Tom's thoughts. I don't think it is impossible at all.'