Games that promote brain training will be tested out.
The Alzheimer's Society and the BBC are running Brain Test Britain to assess whether brain training - such as with hand-held computers - really does work.
Launching on BBC One tonight at 7.30pm, the test will investigate brain training's impact on "mental fitness".
Initial results will be announced early next year but a nine-month trial will continue to assess potential long-term effects.
Research teams from King's College London and Cambridge University will analyse the results.
Children's TV presenter, Richard McCourt, of Dick and Dom, an Alzheimer's Society ambassador, said: "I always wondered if any of these brain training gadgets and games really work.
"I'm looking forward to being trained up and finding out a lot more about how our brains function.
"The more we know about the brain, the nearer we'll come to finding a cure for dementia - and that's the reason why I want to be involved."
Professor Clive Ballard, director of research at the Alzheimer's Society, said: "Every week thousands of people spend time exercising their brain using some form of computer-based brain training, but the jury's still out on whether exercising your brain can boost your brain power.
"As Brain Test Britain asks the question, everyone can help with the answer.
"With one million people set to develop dementia in the next 10 years, it's vital we understand the truth behind the old saying, 'use it or lose it'.
"Join us today and have fun while helping to solve one of the biggest mysteries of the brain: Does brain training really work?"
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