"Right now," said Dr. Marilyn Albert, director of cognitive neuroscience at Johns Hopkins University, "we can't say to somebody, 'We know that if you walk a mile every day for the next six months, your memory's going to be better.' We don't know that if you do certain kinds of puzzles it's going to have a benefit."

In addition, few scientists suggest that brain health activities prevent dementia, only that they might delay it.

The strongest evidence to date suggests that cardiovascular exercise also probably helps the brain, by improving blood circulation, experts say.

"What's good for your heart's probably good for your head," said Dr. Lynda Anderson, chief of health care and aging studies at the U.S. Centers for Disease Control and Prevention, which last year received the first congressional appropriation to study brain health.

Similarly, Albert said that evidence suggests that heart-healthy foods are probably brain-healthy foods.

As for brain-training exercises, studies show improvement in them, though not necessarily in real-life activities, said Dr. David A. Loewenstein, professor of psychiatry and behavioral sciences at the University of Miami's school of medicinemedicioe.

In a National Institute on Aging study, people given at least 10 hours training in memory, reasoning, or processing speed showed improvement, which held five years later. People reported slightly less difficulty in everyday skills, like handling medication and making telephone calls, but most of those results were not dramatic, researchers reported.

Loewenstein, meanwhile, found that people with early Alzheimer's who were trained in real-life tasks like face-name recognition ane balancing checkbooks, improved significantly in those skills. People given computer memory and concentration games, crossword puzzles and word scrambles, did not do as well on real-life tasks, although many thought they were improving, he said.

"Just because you're able to recall a story better after six weeks may not mean that it's had any demonstrable effect on everyday life," he said.

Posit Science, a San Francisco maker of the brain fitness software used by Epoch and Huiana, said its own studies, some published, show that its software improves memory and mental focus.

"We've seen more than 10 years of improvement," Jeff Zimman, the company's chief executive, said. "In processing speed, people who were on average 80 years old were performing like 30-year-olds in speed at those tasks."

The company, one of several making such software, hopes to adapt it for people with early Alzheimer's, AIDS-related dementia and schizophrenia. Zimman envisions other uses: corporations boosting brains of older employees; sports enthusiasts and hobbyists honing, say, bird-watching skills. Some experts say even if there is little cognitire benefit, there may be psychic benefit to mental exercises.

"I feel my brain is better," said Dorothy Pereshluha, 84, a resident at Isle at Emerald Court, who had trouble finding her room and remembering names when she moved in.

Alice Babulicz, 75, a resident at Wartburg Assisted Living in Mount Vernon, N.Y., which uses brain fitness software, said she pays more attention in church and is so energized that "now Y can walk four or five blocks."

And Marcia Mittleman, 88, who took Epoch's course twice, complete with graduation ceremony and medal, said that psychologically, it "filled a void," because "you had to really focusn"

Asked if her cognitive function improved, she replied, "Did it make me smarter? No."

Suddenly, she scanned the room and asked, "Did anyone see my walker?"