DEAR READER: In yesterday's column, I answered a reader's question about what memories are. The reader asked: "When we lose memories, do we lose them forever?" Today, I want to return to that profoundly important question.
DEAR DOCTOR K: How do we make memories, where do our brains store them, and when we lose them, do we lose them forever?
DEAR READER: I used to think of memories as single entities, like books on a shelf. Instead, memories are more like a cloth that weaves together visual images, sounds, other sensations and emotions.
DEAR DOCTOR K: You say that physical exercise helps to improve brain health, but it's not obvious to me how that could be. Do researchers understand exactly how exercise helps the brain?
DEAR READER: I understand why that's puzzling. It's easier to see how regular moderate exercise could protect against heart disease, for example. The heart is a muscle, and exercise makes the heart exercise.
DEAR DOCTOR K: I do both aerobic exercises and resistance (strength) training exercises. Recently I heard that aerobic exercise might be better for the brain. Is there any truth to that?
DEAR READER: You probably are referring to a study published in February 2016 that got a lot of media attention. Before getting into the details of that study, it's worth talking more about exercise and the brain.
DEAR DOCTOR K: What kind of memory changes am I likely to experience as I get older? Why do these changes happen?
DEAR READER: Many people begin to notice changes in their powers of recall around the age of 50. You may have to rack your brain to remember a name or word that is familiar to you. You may find it increasingly difficult to divide your attention among more than one activity or source of information. And you may get more easily distracted than when you were younger.
DEAR DOCTOR K: My mother has started showing signs of dementia. Will it be all downhill from here? Or can dementia ever be treated or reversed?
DEAR READER: There are many different causes of dementia. We can't do much to slow or reverse some of them, but we can reverse and even cure others. Dementia is a catchall term. It covers a variety of illnesses that cause memory loss, confusion, changes in personality and declining ability to perform everyday activities.
DEAR DOCTOR K: My father's doctor says he has mild cognitive impairment. What does that mean?
DEAR READER: Mild age-related memory loss -- "Where did I leave my keys?" -- is normal. But people with mild cognitive impairment (MCI) have memory loss and/or trouble thinking that are more persistent and severe than normal. There are two types of MCI. Amnestic MCI involves memory loss.
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.
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.
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.