For a Sharp Brain, Stimulation By RONI CARYN RABIN | NYTimes.com

AMERICANS may worry about heart disease, stroke and diabetes, but they downright dread Alzheimer’s disease.

For good reason. One in eight adults over 65 is affected by the disease. Those who are spared know they may end up with the burden of caring for a parent or a spouse who is affected. Even though the number of older adults with dementias is rising rapidly, only a few drugs that have been approved to treat symptoms are on the market, and they slow down the disease but do not cure it.

Researchers, however, are more optimistic than ever about the potential of the aging brain, because recent evidence has challenged long-held beliefs by demonstrating that the brain can grow new nerve cells.