Memory – Harvard Health

What is Memory?

As we age, it’s common to worry about losing our memories (That’s partly because a certain amount of age-related memory loss is perfectly normal). In order to preserve your memory as you age, it’s important to understand how memory functions. So, what is memory? Where in the brain are memories stored, and how does the brain retrieve them?

Quite simply, memory is our ability to recall information. Scientists talk about different types of memories based either on their content or on how we use the information. For example, remembering the layout of your grandmother’s kitchen is different in both content and purpose than remembering the middle three digits of a plumber’s phone number while looking at his business card as you dial the phone. The main two categories for memories are short-term and long-term.

Short-term memories involve information that you only need to recall for a few seconds or minutes. If you’re turning at an intersection, the fact that there were no cars coming when you looked to the left is important, but once you’ve made your turn you will quickly discard the information because it is no longer relevant. Keeping it around would unnecessarily clutter your brain.

Long-term memories contain the information that makes you you—not just facts (like the capital of Kansas) or events (like your senior prom) but also skills and processes (like typing or dancing the Macarena). Long-term memory is durable yet changeable; a memory can evolve based on retelling a story or on new information learned after the event.

Memories are not stored in a single location in the brain. Instead, the sensory components of a memory—sight, smell, sound, etc.—are distributed to different areas of the brain, and the act of remembering occurs as the brain pieces those bits back together. Each time a memory is created, its constituent parts are catalogued in the deep-brain structure known as the hippocampus. Next to the hippocampus sits the amygdala, the brain’s emotional center. It flags certain memories as being important or emotionally powerful. The different components of the memory are then distributed mostly to sections of the cerebral cortex, which is the outer layer of the brain.

When it’s time to retrieve a memory, you rely on the part of the brain known as the frontal lobes, which are involved in attention and focus. The pieces of the memory are then pulled from the areas of the cerebral cortex where they’re stored. For example, to remember a scene from your favorite movie might involve pulling in data from the brain’s visual region to recall the backdrop and the actors’ faces, but also information from the language region to remember the dialogue—and perhaps even the auditory region to remember the soundtrack or sound effects. Together, these components form a unique neuronal pattern that lies dormant until you set about remembering it, at which point it is reactivated.

What Causes Memory Loss and Forgetfulness?

Like the rest of our bodies, our brains change with age, meaning that most of us will find ourselves struggling to recall newly learned information or even to think of words we know well. That’s usually not cause for alarm, since some memory loss in elderly people is quite normal and not indicative of memory loss diseases such as Alzheimer’s. But what causes memory loss, and how and why does memory change with age?

Many of the things we think of as normal memory loss with aging can actually be attributed to a slight decline in our ability to perform tasks requiring attention and so-called executive function (planning, sequencing and regulating thought). Specific age-related changes in the brain are associated with that lower executive function. For example, to think of an acquaintance’s name, you must rapidly make connections between brain cells. Each cell (called a neuron) is separated from its neighbors by a tiny gap called a synapse, and a signal from one brain cell must cross that gap to the next one via a chemical messenger called a neurotransmitter. Once across the gap, it must “unlock” a structure called a receptor on the destination cell. With age, both the brain’s chemistry and the structural integrity of the neurons’ wiring deteriorate (The hippocampus, crucial for memory processing, also shrinks). That doesn’t mean you’ll never be able to recall the bit of information that’s eluding you, but it does mean it might take some time for the brain to forge a path to where the memory is stored. Thus most “memory loss” in seniors is actually just a slowing of performance. You can still learn, retain, and recall plenty of information, but it might take you longer—and require a bit more determination—than it did when you were younger.

Some forms of memory loss are caused by head trauma, including brain injuries resulting from high-impact sports such as boxing, soccer and football. Memory loss can be part of a primary brain disease. But it can also happen in people with depression, thyroid malfunction and even vitamin deficiencies, all of which can result in improved memory with appropriate treatment.

We also know that stress, fatigue, sleep deprivation and the feeling of being overwhelmed can contribute to short-term memory loss and forgetfulness. Middle age can be a difficult period of life in which our responsibilities can extend to ourselves, our spouses, our jobs, our children, our parents and even our grandchildren. It’s not uncommon, then, to feel distracted and find it harder to concentrate on things we’re trying to remember.

So how do you know when to visit a doctor for memory loss? If you begin to experience difficulty completing familiar tasks, or have bouts of forgetfulness that extend beyond minor inconvenience and disrupt your day-to-day functioning, there may be something more serious going on than normal age-related memory loss.

What is Mild Cognitive Impairment?

Mild cognitive impairment (MCI) occurs in nearly 20% of adults over age 65. While many people assume it is a precursor to full-blown dementia, fewer than half of people with MCI go on to develop Alzheimer’s dementia within five years. MCI is marked by either memory loss, a decline in cognitive fitness, or both, that is worse than should be expected for the patient’s age.

When the impairment is largely memory-related, doctors refer to it as amnestic MCI. With normal age-related memory loss, people tend to forget fairly trivial things like where they put their car keys. But with amnestic MCI, the things patients forget are more important—who the presidential candidates are, what was discussed in last week’s Zoom meeting, what college your granddaughter attends. Even so, the impairment is considered “mild” because it does not significantly impact day-to-day functions like preparing food, driving and personal hygiene.

The other main subtype of MCI is called non-amnestic. Rather than affecting memory, non-amnestic MCI manifests as cognitive decline in other areas such as language, spatial awareness or the ability to focus and maintain attention. Someone with non-amnestic MCI might find it difficult to keep up with a conversation, pay their bills, make decisions, repair a faucet or understand a speech. Again, however, the impairment is not so severe as to disrupt everyday life.

People whose MCI affects both memory and other types of cognition are said to have multi-domain MCI. Amnestic MCI is the most common subtype.

MCI is highly variable in terms of its severity and trajectory—it may worsen, stay the same or even go away, depending on what’s causing it. Temporary MCI can be brought on by sleep apnea, depression or medications. Risk factors for other kinds of MCI include genetics, stroke, head injury, high cholesterol, high blood pressure, obesity, smoking, and hearing loss. It’s important not to think of these risk factors as “causes” of MCI—instead, each has been associated with the condition.

What is Dementia

Many people confuse mild cognitive impairment (MCI) with dementia. While MCI can in fact be a precursor to the early stages of dementia, dementia is a separate brain disorder. The symptoms of dementia are so severe as to render the patient dependent on others to carry out the tasks of everyday living. But exactly what is dementia

Although memory loss is one of the most common signs of dementia, the disorder often entails other forms of cognitive decline, including a drop-off in the ability to think abstractly, to make reasonable judgments, to speak and understand, and to relate spatially to the environment. Perhaps just as alarming, dementia patients often undergo significant changes to their personalities, becoming agitated and sometimes experiencing delusions.

There are several types of dementia.

Most people know or have heard of someone with Alzheimer’s disease, a type of dementia marked by short-term memory loss so severe that patients often ask the same question minutes apart, forgetting that they have already received an answer. Alzheimer’s patients also frequently experience severe personality changes. People with Alzheimer’s disease have excessive amyloid plaque and neurofibrillary tangles in the brain. But whether these changes are the actual cause continues to be explored. That’s because many older people have similar brain changes but never develop dementia.

Vascular dementia is caused by an interruption of the blood flow to the brain. This can happen after a stroke, brain bleed or head trauma, But more often the cause is reduced blood flow from narrowing of multiple small arteries that feed oxygen and nutrients to the brain. The symptoms are similar to people with Alzheimer’s disease, but it also depends on which parts of the brain are most affected.

Dementia with Lewy bodies arises from an accumulation of harmful proteins in the brain cells causing progressive problems with cognition, memory and movement.

Although Parkinson’s disease is usually thought of as a movement disorder, some people develop symptoms similar to other types of dementia, such as problems with executive function, information retrieval and attention.

Frontotemporal dementia occurs when neurons in the brain’s frontal lobe or temporal lobe die off, leaving the patient to experience personality changes so stark as to be frequently misdiagnosed as psychiatric problems.

The symptoms of primary age-related tauopathy, or PART, can appear similar to those of Alzheimer’s disease. But the symptoms of PART are mostly limited to memory loss and not the other cognitive-behavioral problems usually associated with Alzheimer’s.

People with more than one of these memory loss diseases are said to have mixed dementia.

What is the Difference between Dementia and Alzheimer’s?

Dementia is the generic term for cognitive and memory decline sufficiently severe that the patient requires assistance with everyday functioning. Alzheimer’s disease is the most common cause of dementia, with nearly 5 million Americans affected, but it is by no means the only cause.

Alzheimer’s is a progressive disease, meaning that it worsens over time, sometimes in as little as four years. During the early stages, the patient experiences memory loss but is still able to live independently. In mid-stage Alzheimer’s, the patient may begin to neglect their personal care and to forget significant information. By the late stages of the illness, people require help with even the most basic aspects of daily living, and normal conversation becomes impossible.

What happens to the brain to cause Alzheimer’s? Two substances play a likely role. Both are naturally occurring proteins. Beta-amyloid accumulates in the brain until it forms plaques in the gaps between nerve cells that are conduits for signals that travel through the brain. The other key protein, called tau, also accumulates over time and forms tangles inside the brain cells. The two proteins together kill cells in areas of the brain necessary for memory, personality and other cognitive abilities.

How to Improve Memory and Concentration?

The good news is that, although with age you should expect to experience some forgetfulness, there is plenty you can do to minimize memory loss and even improve and enhance your memory as you get older.

Among the best ways to improve memory are the same lifestyle changes that reduce the risk of heart disease and stroke. For example, quit smoking, drink alcohol in moderation or avoid drinking completely, and limit intake of sugary and processed foods.

But when it comes to how to improve memory, eliminating factors is just part of the puzzle—the other piece is adding in new habits. For example, eating foods that help memory, such as leafy green vegetables, nuts, berries, tea, coffee and oily fish, is a great way to promote your overall health while strengthening your brain.

Regular exercise boosts the growth of brain cells and the production of neurotransmitters, enhancing memory. A mix of aerobic (cardio) and strength exercises is best.

If you’re not getting enough sleep, you might be harming your cognition and memory. Aim for seven to nine hours each night.

Meditation, stress reduction and keeping up a good network of social relationships have all been shown to stave off the effects of aging on the brain.

One key to keeping your mind young is to keep it busy and challenged through lifelong learning and stimulation. Traveling, learning new languages, picking up a musical instrument, taking art or cooking classes, doing puzzles, playing board games—all these things promote the growth of new brain cells and help the brain forge new pathways.
 
Memory enhancement can also come from properly managing your physical and mental health.

If you know or suspect that you suffer from depression, get it treated.

Since many medications can cause brain fog and bouts of forgetfulness, you should review your prescriptions with your doctor and see if dosages can be changed or eliminated. Especially consider drugs with anti-cholinergic properties, such as the older antihistamines (e.g. diphenhydramine, Benadryl), some older antidepressants (e.g. amitriptyline, Elavil), and drugs for urinary symptoms (e.g. oxybutynin, Ditropan).  

Checking your hearing, vision, blood pressure and blood levels of thyroid function and cholesterol may find abnormalities which could easily be addressed and result in improved memory.

Brain experts have developed many tips for improving memory as you attempt to remember such things as names, to-do lists, facts or other information. For example, associating new information with things you already know can help you retain it—like remembering that you’re in parking spot 42 because your son is 42 years old. With another technique, called chunking, you break up a list into categories—if you were memorizing all the countries of Europe, grouping the Baltic States (Estonia, Latvia and Lithuania) lets you see them as one group. Using a more advanced technique, called loci, you “visit” a familiar location in your mind, mentally placing the items you want to memorize at various places along the path.

Certain habitual behaviors will help you remember the information that gets you through your day. One such habit is staying organized—if you always put your car keys on the counter, you won’t have to wonder where you left them. If you write down every appointment or put it into your smartphone, you won’t miss any. If you keep to-do lists, up-to-date address books, and lists of passwords, you won’t face the struggle of trying to recall information when it’s urgent. It’s also helpful to create certain mental habits, such as repeating a person’s name as soon as you’re introduced, paraphrasing parts of a conversation to reinforce the message, and becoming a more careful reader (and re-reader) to really drive home the content.

How to Avoid Memory Loss?

In study after study, physical activity has been associated not just with higher cognitive function but with a decreased risk of memory loss over time. The brains of people who exercise regularly shrink less with age than those of sedentary people (especially the hippocampus, a brain structure key to memory), and their white matter stays healthier. Exercising three or more times per week has been associated with a 40-50% lower risk of diagnosis with dementia.

In one study, adults at a high fitness level were 88% less likely than those of medium fitness to develop dementia, and high fitness appeared to delay the onset of dementia by 11 years. To reap the benefits of exercise, you must be consistent, so set aside a dedicated time for exercise and stick with it. Swimming, walking and tennis are great activities. Joining a gym and taking fitness classes works very well for some people, since socialization is known to boost brain health.

Another way to avoid memory loss is to be mindful of what you eat. While some specific foods are associated with brain health, food marketers sometimes exaggerate their benefits. That’s why it’s better to think in terms of broad patterns and styles of eating. One rule of thumb is to build your eating habits around foods that are good for your heart, since the same diet that is heart-healthy is also good for the brain. You may have heard of the Mediterranean diet, which has been shown to promote heart health. It centers on plant-based foods, fish, nuts and olive oil. A variation of the Mediterranean diet, called the MIND diet (Mediterranean diet Intervention for Neurodegenerative Delay) was designed with the explicit goal of optimizing brain health. It’s heavy on leafy green vegetables, nuts, berries, fish and poultry, and avoids red meat, butter, cheese and sweets. In one study, MIND diet adherents were 30-35% less likely to score poorly on cognitive tests.

But what about memory supplements? Can’t you simply take an over-the-counter pill or capsule to get a memory boost? Unfortunately, marketers frequently make unproven claims about the benefits of these products. For example, ginkgo biloba is often touted as a wonder supplement for mental function, but numerous studies have found that it has no effect on memory, attention or risk of dementia. You do need certain vitamins for memory, but studies have not shown that taking more than the recommended daily allowance (RDA) has a beneficial effect. Still, B vitamins and vitamin D might merit special attention, since they’re particularly important for keeping dementia at bay. A blood test can tell you whether you’re vitamin B12-deficient, in which case a supplement is a good idea. You can get plenty of vitamin D through 10-15 minutes of sun exposure daily, but if that’s not possible, a supplement may be called for.

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