Searching the internet may help middle-aged and older adults keep their memories sharp, say US researchers.

Researchers at the University of California Los Angeles studied people performing web searches while their brain activity was recorded with functional magnetic resonance imaging scans.

"What we saw was people who had internet experience used more of their brain during the search," says Dr Gary Small, a UCLA expert on aging.

"This suggests that just searching on the internet may train the brain - that it may keep it active and healthy," says Small, whose research appears in the American Journal of Geriatric Psychiatry.

Many studies have found that challenging mental activities such as puzzles can help preserve brain function, but few have looked at what role the internet might play.

"This is the first time anyone has simulated an internet search task while scanning the brain," he says.