I've been reading up on the relatively new scientific discipline of brain development.

Much of the focus has been on early childhood development. If you have small children, you've probably heard about the importance of mental stimulation.

The library can and, for many families, does play a big role in precisely this. In fact, we're reworking our storytimes to take better advantage of the research to make sure that when children reach school age, they are truly ready to read.

But this week, I'd like to talk about something else: what happens to the brain as it ages?

Here's the good news. The old stories about losing brain cells aren't true. Brain cells continue to generate. More important, the brain continues to make new neural connections -- trunks and branches of nerve cells and pathways that grow always more complex.

But recent research suggests something intriguing. The side of the brain that is used to explore the world, to find new things, does slow down.

The other side of the brain, though, begins to really pick up. Instead of being optimized to acquire information, now the brain starts focusing on something different: the recognition of patterns. So while it may take a little more effort to lay down new neural tracks, it's much, much easier to make sense of the world, extrapolating from previous information.

This pattern recognition goes by many names. Experience. Knowledge. Wisdom, even.

Research also shows something else. As the brain ages, it doesn't have to deteriorate. Or rather, these four activities can keep the mind sharp, even, in some cases, compensating for many symptoms of Alzheimer's Disease.

* Exercise the body. Walking has been shown to have remarkable long term benefits on the health of the brain.

* Exercise the brain. Read! One surprising finding is that the brains of well-educated people tend to do better than those of folks who have done mostly manual labor. Why? Because an education inclines people to continue to seek mental stimulation. Reading leads to thinking, thinking leads to understanding, and the activity of understanding leads to a longer and healthier life.

Incidentally, some kinds of puzzles are proven brain builders. Crossword puzzles, chess puzzles, jigsaw puzzles are all excellent. Just last weekend, I seem to have gotten myself addicted to sudoku, the 81-square logic puzzle involving numbers 1-9.

Another powerful mind-building activity is music. Get back to an old instrument, or take up a new one. I just signed up for 5 string banjo lessons from Denver's Swallow Hill, and am enjoying it immensely. I'm also finding that library books and videos are almost as good. (Note to older students: our parents were right. Practice makes a difference.)

Here's one that seems to encourage a really astonishing amount of brain development, even late in life: learn a new language. Chinese, anyone?

* Have an active social life. This is one of the key predictors of a long life. The brain is wired for interaction. Other people are so funny and fascinating, so unpredictable and unchanging, so perplexing and paradoxical, that they keep you involved, keep you guessing, keep you alert. Join a Rotary club, a church, a bridge club, run for office, become a volunteer. Talk to people.

* Eat right. Spend more time at the salad bar, and less time at the potato bar.

The bottom line: the almost 80 million Baby Boomers are about to join the ranks of our existing seniors. They, we, can either be a significant drain on society, or productive, contributing, and interesting citizens.

So don't wait to get that brain in shape. Your membership in the mental health club of the library is already paid up. Come on down!