Scientists are reporting the first compelling evidence in people that cognitive training can boost levels of a brain chemical that typically declines with age.

A 10-week study of people 65 or older found that doing rigorous mental exercises for 30 minutes a day increased levels of the chemical messenger acetylcholine by 2.3% in a brain area involved in attention and memory.

The increase "is not huge," says Étienne de Villers-Sidani , a neurologist at McGill University in Montreal. "But it's significant, considering that you get a 2.5% decrease per decade normally just with aging."

So, at least in this brain area, cognitive training appeared to turn back the clock by about 10 years.

The chemical change observed after intensive brain training is persuasive, says Michael Hasselmo

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