In addition to mental training, other lifestyle choices also have been found to promote good brain health. These include maintaining aerobic fitness, doing mentally challenging work and sticking to a healthy diet.

Scientists have known for years that as we get older, the brain tends to function less efficiently, and electrical currents connecting different areas of the brain get weaker. Now studies have shown that this gradual deterioration can be reversed.

"Our bodies are getting healthier, and we're living much longer, and the biggest threat now to being able to function well and productively when we're older is in the functioning of the brain," Professor Ian Robertson said yesterday.

Brain Is Plastic

"Over the past few years, neuroscientists have made the quite revolutionary discovery that at all ages, the brain is plastic or flexible -- that's to say, it's shaped by experience, what we do and how we think."

Prof. Robertson, who was presenting his latest research on aging to the British Association for the Advancement of Science's annual conference in Dublin, has just completed a study involving volunteers over the age of 50 whose brain performance was measured before and after mental training.

The results, to be published later this year, show "very significant" improvements in mental capabilities after just a few days of training. This is in line with recent research in America which showed that the mental age of 60-year-olds could be reduced by 14 years after a three-week mental training session.

"We've found that with mental training we can enhance certain types of function in elderly people by stimulating activity in the frontal lobes of the brain," said Prof Robertson, a 54-year-old neuro-psychologist at Trinity College, Dublin, who has just published a book in Britain entitled Stay Sharp with the Mind Doctor.

He said anyone could keep their brain young and alert well into old age by following a simple mental training program. This includes taking time to stop and think about what you are doing and getting into the habit of making a mental picture of a given set of tasks so details can be easily recalled.

Attention System

"We're all familiar with older people who tell the same story again and again without realizing they've told it before to the same person. As we get older, we tend not to use our attention system, our ability to concentrate on what's going on around us, because we tend to think we've seen it all before, and we see what we expect to see rather than what's actually there.

"As this happens, our frontal lobes, the attention system in the brain, is switched off.

"This is when we start behaving in an absent-minded way -- for example, you might forget your keys or get into your car and go to your place of work without remembering that you shouldn't be at work that day."

Apart from mental training, other aspects of a person's lifestyle changes have also been found to promote good brain health. These include maintaining aerobic fitness, doing mentally challenging work and sticking to a healthy diet.

"Medical advances have created a fourth age of humankind intermediate between middle and old age, and this is the new prime of life," said Prof Robertson.

"Biologically and psychologically, old age need not now begin until the eighties for many people."