If those 'mad moments'--when you can't remember what your friend has told you or where you left your keys--are becoming more frequent, mental exercises and a healthy brain diet may help. Just as bodies require more maintenance with the passing years, so do brains, which scientists now know show signs of aging as early as the 20s and 30s. 'Brain aging starts at a very young age, younger than any of us had imagined and these processes continue gradually over the years,' said Dr. Gary Small, the director of the Center on Aging at the University of California, Los Angeles. 'Tin convinced that it is never too early to get started on a mental or brain-fitness program,' he added. In his book, The Memory Bible, the 51-year-old neuroscientist (神经学家) lists what he refers to as the 10 suggestions for keeping the brain young. They include training memory, building skills, reducing stress, mental exercises, brain food and a healthy lifestyle. 'Misplacing your keys a couple of times don't mean you should start labeling your cabinets. Memory loss is not an inevitable consequence of aging. Our brains can fight back,' he said. Small provides the weapons for a full-scale attack. Simple memory tests give an indication of what you are up against and tools such as 'look' and 'connect' are designed to make sure that important things such as names and dates are never forgotten. 'So if you wanted to learn names and faces, for example, you meet Mrs. Beatty and you notice a distinguishing facial feature, maybe a high eyebrow,' said Small. 'You associate the first thing that comes to your mind. I think of the actor Warren Beatty, so I create a mental picture of Warren Beatty kissing her brow.' Small admits it may sound a bit strange but he says it works. 'Mental exercises could be anything from doing crossword puzzles and writing with your left hand if you are right handed or learning a language. It could be anything that is fun that people enjoy doing,' he added. The 'mad moment' in the first paragraph refers to the time when we ______