It's common knowledge that a proper exercise regimen can do wonders for the body. Only recently, however, have psychologists and gerontologists aggressively applied the same principle to the mind.

Among people who work with older adults, the concept of "cognitive fitness" has become a buzzword to describe activities that stimulate underutilized areas of the brain and improve memory. Proponents of brain-fitness exercises say such mental conditioning can help prevent or delay memory loss and the onset of other age-related cognitive disorders.

"Most people's idea of fitness stops at the neck," said Patti Celori, executive director of the New England Cognitive Center. "But the brain is the CPU of our body, and most people don't do much to keep it as fit as possible."

The NECC runs one of a growing number of programs that work with older adults to improve cognitive abilities. Activities include computer programs designed to stimulate specific areas of the brain, replication of geometric designs using boards with pegs and rubber bands, and visual and auditory memory exercises.

Some of the other programs are Maintain Your Brain, initiated a year ago by the Alzheimer's Association; Mind Alert, run by the American Society on Aging; and other regional programs such as the Center for Healthy Aging in Kent, Ohio.

For do-it-yourself types, a plethora of books have been published on getting the brain in shape. Paula Hartman-Stein, a geropsychologist at the Center for Healthy Aging, recommends The Better Brain Book, by David Perlmutter and Carol Colman, and The Memory Bible by Gary Small.

One purpose of mental exercises is to reinforce the idea that "in aging, not everything is downhill," said Elkhonon Goldberg, a Manhattan neuropsychologist and author of The Wisdom Paradox, which examines how some people grow wiser with age.

"There are gains that are subsequent and consequent to a lifelong history of mental activity and mental striving," Goldberg said. He also believes brain exercises can benefit adults suffering from mild cognitive impairment, and he has developed computer puzzles designed to help them stimulate different areas of their brain.

It's not clear how much targeted brain exercises can prevent the onset of cognitive disorders in older adults. But some findings indicate that high cognitive ability is tied to a lower risk of Alzheimer's.

One of the most extensive and widely cited investigations on the subject, the landmark Nun Study, tracked 100 Milwaukee nuns who had written autobiographies in the 1930s. More than 50 years later, scientists gave them cognitive tests and examined the brain tissue of nuns who died. Those who demonstrated lower linguistic ability in the autobiographies were at greater risk for Alzheimer's disease.

A similar study published in the Journal of the American Medical Association surveyed 801 older Catholic nuns, priests and brothers. The results linked reading newspapers and participating in other brain-stimulating activities with a reduced risk of Alzheimer's.

A 2000 National Research Council report commissioned by the National Institute on Aging found some brain exercises were worthy of government funding.

But skeptics question whether beginning an active regimen of brain teasers late in life will do much to prevent brain disorders.

Research to date provides scant evidence that mental exercise can stave off dementia, wrote Margaret Gatz, a psychology professor at the University of Southern California, in an article published by the Public Library of Science.

Gatz wrote in an e-mail that she would be more convinced if researchers randomly assigned cognitive training, then followed study subjects over several decades.

She also said she was concerned that too much emphasis on the benefits of mental fitness could stigmatize Alzheimer's patients.

"If mental exercise is widely believed to prevent (Alzheimer's disease), then individuals who do become demented may be blamed for their disease on the grounds of not having exercised their brains enough," she said.

Still, supporters of cognitive-fitness programs are pushing for greater recognition from the federal government. During December information-gathering sessions leading up to the White House Conference on Aging, conference representatives said several speakers have made a case that brain health ought to be promoted in much the same way that physical fitness is today.

Few people see much downside in pursuing brain-stimulating activities, said Nancy Ceridwyn, special-projects director at the American Society on Aging. Puzzles, spelling practice, memory exercises or book discussions don't pose much harm.

That said, Ceridwyn isn't convinced that all the brain exercises being offered today are practical. She wonders whether workbooks that ask adults to do pages of math problems to get their brains in gear might be unnecessarily torturing people in their twilight years.

"How many people are going to get up and say, 'I'm excited about doing my multiplication tables today'?" she said. "Not many."