[简答题]

Researchers have established that when people are mentally engaged, biochemical changes occur in the brain that allow it to act more effectively in cognitive areas such as attention and memory. This is true regardless of age.
People will be alert and receptive if they are faced with information that gets them to think about things they are interested in. And someone with a history of doing more rather than less will go into old age more cognitively sound than someone who has not had an active mind.
Many experts are so convinced of the benefits of challenging the brain that they are putting the theory to work in their own lives. "The idea is not necessary to learn to memorize enormous amounts of information," says James Fozard, associate director of the National Institute on Aging. "Most of us don’t need that kind of skill. Such specific training is of less interest than being able to maintain mental alertness." Fozard and others say t