We all know what we should do to increase physical fitness. But how can we increase the fitness of our brains? While taking your mind for a jog isn't an option, giving it regular exercise is. The concept of training your brain is gaining credibility, and now it's become the computer games industry's latest big idea, with four new games just out to help people to flex their mental muscles.

Whether you choose to try to reduce the age of your brain to 20 (purported to be the ideal brain age in Nintendo's How Old is Your Brain?), or make your brain bigger by using another Nintendo game, Big Brain Academy, or improve your "Practical Intelligence Quotient" and post your score with the help of a Sony games title, there's no shortage of new ways to train your brain.

1) What is brain training?

Recent research suggests that everything from absentmindedness to arithmetic skills can be improved by playing certain intelligence and memory-stimulating activities. Scientists and neuro-experts believe puzzles that rely on problem-solving, memory and logical deduction can be highly beneficial for the brain by making people approach tasks in a more flexible way. A widely held belief used to be that the brain only lost cells as it got older. Now it's known that people can acquire new brain cells throughout their lives, provided their brains are stimulated.

According to the Society for Neuroscience, remembering lists of facts or keeping day-to-day information in your mind is different from memorising things in the long term. To do this, you have to exercise your brain. One way is to play a dedicated computer game such as Nintendo's How Old is Your Brain? or Big Brain Academy. Typical tasks in How Old is Your Brain? could be counting the syllables in a sentence to completing 20 simple sums as quickly as possible.

2) How does it work?

Dr Ryuta Kawashima, the neuroscientist who is behind the Brain Trainer device (which is like a large calculator but with simple graphics and sound) and the Nintendo Dual Screen (DS) title Brain Training: How Old is your Brain? explains how it all works. "Simple mathematical calculations and saying answers out loud activates the brain, particularly the prefrontal cortex which governs the most essential living functions for humans, such as cognition, emotion and memory, and enables the maintenance and improvement of brain functions."

Nintendo's DS handheld games console has one screen that's touch sensitive and is "drawn" or written on using a stylus, and another that displays information and instructions. Users hold the device like an open book. Like Dr Ryuta Kawashima, Dr Sarah-Jayne Blakemore, a cognitive neuroscientist and author of The Learning Brain, thinks that this really will help to make your brain more active.

"When you're stimulating your brain, it is more active and can even grow brain cell connections. If you teach people to play the piano, the part of the brain that controls finger movements increases and is more active. That's the idea behind brain training."

3) Why now?

Dr Blakemore says there are two reasons for the interest in brain training. "People are living longer, so they are noticing that their memories are going sooner, or they're aware of it over a longer period. They care about that because there's more awareness of about brain health. There's also scientific evidence showing that training your brain improves it."

4) What do the experts say?

Specialists agree that exercising your brain is a good thing. Dr Kawashima says: "If you don't use your brain, it will age quickly. You'll have a brain with less power than the ideal brain age of 20. But you can train your brain just like your body."

Psychologist Professor Walter Furneaux agrees that this kind of mental stimulation is valuable. "It's true to say that almost any mental rehearsal can be useful to improve memory [and mental agility]. While I don't know of any specific results about these games, it would be interesting to do some serious work on them."

Dr Marshall D Voris conducted a study using the brain-training exercises available at www.mybraintrainer.com, a website that offers daily challenges to keep the minds of its online users alert. He claims that "the MyBrainTrainer.com exercises increased IQ, reduces anxiety, and improves cognitive efficiency and speed".

5) Who should do it?

It's said that doing puzzles can slow the onset and progression of Alzheimer's disease and improve mental capacity in the young. According to a study into the effects of Alzheimer's by the Case Western Reserve University in the United States, middle-aged people who kept active, mentally or physically, were less likely to develop the disease in later life. Activities such as gardening, playing a musical instrument or exercising were found to be the most successful in helping to prevent the disease.

6) How do I train my brain?

Dr Blakemore cautions there's only so much any exercise can do. "If you play the Nintendo game or solve crossword puzzles you become better at those tests but you're not suddenly going to become a brilliant cook or something. It's very specific."

So you may be able to boost your IQ by a point, but the great novel may take a little more time.

Low-tech brain workouts

* Solve puzzles

Riddles, crosswords, sudoku and Scrabble are all reported to greatly improve brain function and memory, and decrease mental decline.

* Get plenty of sleep

Aim to get eight to nine hours of sleep regularly. Being awake for 21 hours straight decreases your mental agility to that of someone who has been drinking.

* Don't skip breakfast

Those who miss breakfast have far lower levels of concentration. For best results, eat within an hour of waking up and choose food high in fibre, protein and carbohydrate.

* Get plenty of exercise

Physical activities are proven to improve abstract thinking and concentration, promoting the growth of brain cells.

* Learn another language

Language learning provides a great mental workout, forcing your brain to switch tracks constantly. It also helps tone the frontal lobes, which decline with age.

* Break your routine

Breaking at least two habitual actions a day keeps your brain active. Try altering your route to work or using your "wrong" hand for your mouse.

* Eat well

Scientists recommend sunflower seeds, dark berries, unrefined grain foods (brown rice, pasta and wholemeal bread), oily fish and minimal amounts of caffeine.

* Drink plenty of water

Aim for eight glasses every day - dehydration can affect concentration levels.

Your guide to mind games

Although not a cheap option, the current crop of brain-training computer games are a fun way to try brain-boosting.

DR RYUTA KAWASHIMA'S 'BRAIN TRAINING: HOW OLD IS YOUR BRAIN'

Price Nintendo DualScreen (DS) to play game on, £99.99, Brain Age £19.99

What it does This handheld game allows people to train their brain on a regular basis by completing a series of number, logic and memory-based exercises. It gives users a 'brain age' that is based on their speed and accuracy.

Available from www.amazon.co.uk

'BIG BRAIN ACADEMY'

Price Nintendo DS to play game on £99.99, Big Brain Academy, £19.99

What it does Although similar in to Brain Training, this game claims to help build your brain size. More visual tasks mean it's great for boosting spatial awareness.

Available from www.amazon.co.uk

'PQ: PRACTICAL INTELLIGENCE QUOTIENT'

Price Sony PSP to play game on £179, PQ £24.99

Fewer cartoons and with more futuristic graphics, PQ is released later this month. Although the game doesn't tell you how old your brain is, it will instead give you a Practical Intelligence Quotient score that can be posted on an online forum.

Available from www.amazon.co.uk

WWW.MYBRAINTRAINER.COM

Price $9.95 (about £4.40) for four months' membership

What it does As well as offering tailor-made brain-training exercises, this site provides users with a brain diary so they can monitor their brain's speed and agility at different times of the day, eg after drinking caffeine, eating, running and so on.

Available from www.mybraintrainer.com

BRAIN TRAINER

Price £29.95

What it does For anyone reticent about investing in a hand-held games console, this device is a good compromise between hi-tech and low cost.

Based on the same research as Dr Ryuta Kawashima's Brain Training: How Old is Your Brain?, this calculator-like device is a less expensive way to train your brain than paying out for a Nintendo DS.

Available from www.firebox.com