Bonn, Germany - A man sits on a train solving a crossword puzzle, a woman broods over a Sudoku grid while an ad for an electronic memory game flashes across a television screen. There is no shortage of ways to improve the brain's memory powers - after all, lots of people want to improve their mental abilities.

But are Sudoku, crosswords and other training games any good at improving memory? Are they really effective in training the mind or just a nice way of passing the time?

"If you train your brain, you can improve your performance," says Carsten Brandenburg from Germany's Memory Training Association. But not every exercise can radically change a person's ability to remember things.

"If you repeat the same kind of exercise, your mind gets into a routine, and there is no challenge anymore," says Brandenburg.

Sudoku is most effective in the initial stages. "The brain is not used to thinking in that manner and that's why new connections are made between the individual nerve cells," explains Brandenburg.

The chairwoman of the Professional Association of German Psychiatrists, Christa Roth-Sackenheim says, "We have recently come to understand that the human brain can make new connections and even new paths."

That explains why Sudoku and computer memory games can have a positive effect on the brain's memory performance. "You don't just improve your concentration, you also practice strategic thinking and how to link different facts," explains the psychiatrist. That ability can be useful in daily life.

The most effective puzzles are those that test more than your existing knowledge which excludes puzzles such as crosswords.

There are a number of books and games for electronic consoles that go in that direction, according to Brandenburg, who also works as a memory coach at Germany's Memory Clinic in Essen.

"The best exercises are well designed and gradually become more challenging as they progress," he says.

But computer games and electronic memory puzzles are not all-purpose weapons against memory loss, says psychiatrist Michael Rapp from Berlin's Charite University Hospital.

"There is no exercise that can make a person more intelligent overall," says the head of the clinic's geriatric psychiatry working group.

You don't need to buy expensive games to keep your brain fit. If you follow a few pointers every day, you will improve your memory or at the very least, keep it at the present level.

"Communicating is essential," says Brandenburg, adding, "That's how you learn to query things, gain new knowledge and grapple with questions."

Another way of improving memory is to learn a new language, according to Roth-Sackenheim. Listening to music, doing domestic chores alone or pursuing a hobby can also help.

"Engaging in physical exercise is important for all age groups," says Roth-Sackenheim. "That's because sport trains the brain because you have to remember certain physical movements and practice your coordination."

There is another alternative - keeping busy with your grandchildren. When elderly people try to understand young people's lives, they also exercise their brains.