But what scientists do know now that they didn't just a decade ago is that people generate new brain cells, and new connections between them, throughout life. Mental stimulation is one key. The more you challenge your brain, the more new nerve pathways you form. A mini-industry of brain teasers, puzzles and computer games has sprung up to help worried baby boomers do just that. But you can give your brain a good workout with just a few modifications in your daily life. Some of the niftiest are "neurobics" -- a term popularized by the late neurobiologist Lawrence Katz for...