What does neuropsychological testing involve?

DEAR DOCTOR K: My husband's doctor suspects that he has Alzheimer's disease and wants him to have neuropsychological testing. What will these tests involve?

DEAR READER: There is no single test that can diagnose Alzheimer's disease. In fact, a doctor cannot make the diagnosis with absolute confidence without studying the brain under the microscope, which is rarely done except in an autopsy. Alzheimer's disease is diagnosed presumptively by a combination of different types of evidence. The disease typically has a slowly progressive onset. Sudden confusion or speech problems, for example, are not caused by Alzheimer's.

Is too much sleep harmful to your memory?

DEAR DOCTOR K: I read about a new study on sleep and memory. I understand why too little sleep could affect memory. But why would too much sleep be harmful?

DEAR READER: When it comes to memory, sleep is a Goldilocks issue: Neither too much nor too little is good.Aim for "just right," says Dr. Elizabeth Devore, an instructor in medicine at Harvard-affiliated Brigham and Women's Hospital. Dr. Devore led a new study that suggests getting an "average" amount of sleep -- seven hours per day -- may help maintain memory in later life.

How does regular exercise help prevent memory loss?

DEAR DOCTOR K: I'm in my late 60s. I've read that regular exercise helps prevent memory loss. I find that hard to believe. How does it do that? And how much exercise do I need to reap this benefit?

DEAR READER: It's easy to understand why regular exercise would be good for your bones, muscles, lungs and heart. Regularly challenging those organs would make them stronger.

Why do I have trouble remembering certain types of information but not others?

DEAR DOCTOR K: As I get older, I've noticed that I have more trouble remembering certain types of information. But other types of memory are as strong as ever. Is this true, or just wishful thinking on my part?

DEAR READER: You've made an interesting observation -- and an accurate one. As we age, some information does become harder to recall, and new memories may be harder to lay down in the brain. But other memories remain as accessible as ever.

How do our brains create memories?

DEAR DOCTOR K: How do our brains create memories? Are our memories stored in some sort of "memory bank"?

DEAR READER: A memory is not a single entity, like a book on a shelf. It is more like a cloth that weaves together multiple facets of sensory, emotional and factual information. Different areas of the brain process and store different aspects of a memory.

How can I maintain my executive function as I age?

DEAR DOCTOR K: I recently read that aging affects something called "executive function." Could you please explain what this is?

DEAR READER: Executive function is an umbrella term for the complex thinking required to make choices, plan, initiate action and inhibit impulses. You can think of executive function as your "inner CEO."

How can I improve my memory?

DEAR DOCTOR K: As I've gotten older, I've started to forget things here and there. Can you give me some strategies for improving my everyday memory?

DEAR READER: Believe me, you're not alone. Most of us experience more forgetfulness as we get older. And most of us who become a little forgetful don't have, and never will have, Alzheimer's disease or another type of dementia. Fortunately, there are plenty of behavioral strategies you can use to improve your memory. Many are simple things that you probably do already. But you still can benefit from doing them more regularly.

What percentage of our brains do we really use?

DEAR DOCTOR K: I've heard it said that we use only 10 percent of our brains, but I'm skeptical. Could it be true that we use only this small percentage of our brain capacity?

DEAR READER: Many parts of our bodies have some extra capacity built in. You can have an entire lung or kidney removed and get along fine with the one that remains. Your body can spare skin and bone marrow. If your appendix, gallbladder or spleen needs to go, so be it — you can live without these organs if you need to.

Are memory problems always a sign of dementia?

DEAR DOCTOR K: I am in my mid-60s, and I'm worried I might be getting more forgetful than normal for my age. I function fairly well most of the time. But sometimes I'll forget something like the details of a phone conversation I recently had. How can I know what's normal?

DEAR READER: You sometimes forget things you didn't used to forget? Well, join the club. Each of us has more difficulty remembering things as we get older -- it's a normal part of aging. Like thinning hair and stiffer joints, subtle memory problems are common.

What is hospital delirium?

DEAR DOCTOR K: A friend recently told me that his elderly aunt had to stay a few days in the hospital after a surgery. While there, she developed mental confusion that he called delirium. What surprised me was that he said this is fairly common. Why would a hospital stay cause delirium?

DEAR READER: Being a hospital patient can be a frightening experience for anyone. Unfortunately, some patients -- particularly older ones -- develop delirium. This can make the hospital experience truly terrifying.