Why do Alzheimer's patients remember certain things and forget others?

Alzheimer's disease affects recent memories first. The retention of new information is most affected, while recollections of things that happened in the past are much more resistant. The loss of recent events is often one of the first, if not the first, symptom of the disease.

Because the changes of Alzheimer's come on so gradually, it's usually hard to pinpoint when the first symptoms appeared. What's more, the memory loss can initially be pretty subtle. (And in today's hectic world, everybody has some memory lapses now and then.) It often takes a year or longer to realize that the situation is getting worse and that the memory loss is not just occasional but consistent and unusual for the person.

Typically, memories that are well encoded are those your father will remember best. He's had lots of practice recalling those memories over the years. While you may not consciously remember your fourth-grade teacher, your mind rehearses that memory on its own and its ability to be recalled gets strengthened.

Eventually, long-term memories will be affected as well, and even in the early stages of the disease, it may become more difficult for your dad to accurately recall some things that happened a long time ago.