Talk about an intriguing and very confusing puzzle! Does the exhibition of symptoms of Alzheimer's disease mean that a person actually has a tangle-filled brain? And what does the brain of a person who is mentally sharp when he or she dies look like?

Prior to her death. Recently, I had the opportunity to hear Dr. David Snowdon, the author of "Aging with Grace: What the Nun Study Teaches Us About Leading Longer, Healthier and More Meaningful Lives," during an Alzheimer's Symposium held at...