People in the debilitative, or negative, imagery group reported feeling much less confident in their ability to improve their performance, she said. Her research with dancers also revealed that elite performers have better control of the imagery that they use and so are less at the mercy of intrusive negative imagery.

In addition to this scientific support, imagery has many famous advocates including Tiger Woods, Roger Federer, and Jonny Wilkinson. However, the underlying mechanisms that make it effective remain unclear.

The answer may come from studying imagery from the perspective of a neuroscientist, believes Dr Martin Edwards, a lecturer in Human Movement, also from the School of Sport and Exercise Sciences.

"Early research measured activity in single brain cells in monkeys when they were performing specific movements," explains Dr Edwards. "It was found that the same cells were activated when monkeys simply watched an action, even without actually performing the task." These brain cells were named "mirror neurons" and have since been found in humans, he says.

This finding may explain why watching someone else execute an action can improve your own performance, says Dr Edwards. Importantly, if similar circuits are activated by imagery as well as observation, it may also explain the benefits seen with mental rehearsal, he explains.

The mirror neurons are found in the premotor cortex. This is an area of the brain usually associated with eliciting co-ordinated movements involving sequences of muscle movements or the combined movement of many muscles, such as those used in sporting movements.

Research using functional Magnetic Resonance Imaging is required to establish whether the same brain areas are activated during imagery as during movement, says Dr Edwards. This technique allows scientists to watch changes in blood flow to the brain, to reveal which areas are being used in real time.

While the involvement of mirror neurons in imagery has yet to be fully explored, neuroscience is already influencing the way sport psychologists use imagery. "Brain research is challenging some of our long held beliefs," says Dr Cumming. "It can aid our understanding of how to design interventions more effectively."

"For example, common practice is to advocate the use of relaxation training prior to imagery, but with advances in brain research, that idea has changed," explains Dr Cumming. Instead, it has been demonstrated that it is important to match imagery to the physical environment in which the exercise takes part, she said.

Imagery may not be the sole reserve of elite athletes. The researchers believe that it could also help rehabilitate motor skills in patients. "If we can show conclusively that imaging a movement can facilitate execution by these pathways, then patients can be sat in bed but still practising their movements," explains Ramsey. "The power of imagery is that you can do it anywhere," he said.

• Vikki Burns is one of the winners of the National Brain Science Writing prize, announced today. Other winners are: Eleanor Barrie; William Davies; and Martin O'Neill.

The competition is a collaboration between the three largest public-focused brain organisations in the country: At-Bristol's "Your Amazing brain" website; The European Dana Alliance for the Brain and The British Neuroscience Association.

Dr Penny Fidler, neuroscientist and organiser, said: "We wanted a competition that would celebrate the astounding and fast-moving field of brain science. To intrigue people and make them talk, think and question how amazing their brains are.

"We also wanted to encourage brain scientists across the UK to tell the world about their research in a lively and intriguing way, and we're delighted that three out of the four winners are scientists."