Why We Forget and How to Remember Better, page 16
When It’s Not Normal Aging
Now that you have a better understanding of the changes in memory that occur with normal aging, we’re going to turn to understanding memory loss. Keep in mind that when older individuals develop a brain disease affecting thinking and memory, they will typically experience all the changes that occur in normal aging plus the changes that come with the brain disease.
Memory Loss Terminology
The terminology used by clinicians and researchers to describe memory loss and the individuals who have it can be quite confusing. In this section we will describe the general syndromes that can apply to many underlying brain problems (such as dementia, mild cognitive impairment, and subjective cognitive decline, progressing from most to least severe), and then we’ll dive into the specific brain disorders (such as Alzheimer’s disease, vascular dementia, and frontotemporal dementia) in the next section.
Dementia
Dementia is not a diagnosis in and of itself. Dementia is a term that means an individual has experienced progressive decline in their thinking and memory severe enough to interfere with day-to-day function. Dementia is considered to be mild if the individual has difficulty only with somewhat complicated daily activities, such as paying bills, shopping, preparing meals, or taking medicines. If the individual has difficulties with more basic activities of daily living, such as dressing, bathing, eating, or using the toilet, the dementia is considered to be in the moderate or severe stage. Most people with dementia become more impaired over time, depending on the cause. Different causes of dementia affect different brain regions, producing different symptoms (see Figure 13.1).
Figure 13.1. A small amount of brain shrinkage occurs in normal aging. Parietal and temporal regions shrink in Alzheimer’s dementia. Frontal and temporal regions shrink in frontotemporal dementia. Strokes damage the brain in vascular dementia.
Mild Cognitive Impairment
We use the term mild cognitive impairment when (1) a decline in thinking and/or memory has been noticed by the individual, their family, or their doctor, (2) impairment—typically mild—is present on tests of thinking and/or memory, and (3) their daily function is essentially normal, although activities may require a bit more effort. Note that because their daily function is essentially normal, by definition individuals with mild cognitive impairment do not have dementia. Research suggests that approximately half of people with mild cognitive impairment end up declining over time and developing dementia at a rate of about 5% to 15% per year, whereas the other half remain stable—or actually improve.
Subjective Cognitive Decline
Some individuals are concerned enough about their memory function to see their doctor, but their performance on tests of thinking and memory is normal, as is their daily function. These individuals have subjective cognitive decline. Most people with subjective cognitive decline are simply worried about their memories and there is actually nothing wrong with them. There are some people, however, who have noticed a slight but real decline in their thinking or memory despite their performance being normal on standard cognitive tests. For this reason, when compared to individuals without concerns about their memory, a few people with subjective cognitive decline are somewhat more likely to end up with a diagnosable memory disorder over the next 5 to 10 years.
Alzheimer’s Disease
In 1907, Alois Alzheimer described the case of a 51-year-old woman he observed in the insane asylum of Frankfurt am Main. “Her memory is seriously impaired,” he wrote. “If objects are shown to her, she names them correctly, but almost immediately afterwards she has forgotten everything.”1 He goes on to describe what he saw in her brain under the microscope after her death, including the neurofibrillary tangles, “only a tangle of fibrils indicates the place where a neuron was previously located,” and amyloid plaques, “minute miliary foci which are caused by deposition of a special substance in the cortex.” Although this brief description in Alzheimer’s own words (translated from German) concisely summarizes this disease of memory caused by tangles and plaques, we’ll expand a bit regarding the common memory deficits observed.
Memory Loss Progresses but Awareness Diminishes
Because Alzheimer’s disease progresses slowly over about 4 to 12 years, most individuals with Alzheimer’s will go through the mild cognitive impairment stage before they develop dementia, as do individuals with other causes of dementia. Some individuals will experience subjective cognitive decline prior to mild cognitive impairment. Once function is impaired and Alzheimer’s disease dementia is diagnosed, the disease progresses from the mild to the moderate and then to the severe stage. In the mild cognitive impairment and mild dementia stages, individuals with Alzheimer’s are often very aware of their disease and distressed by their memory problems. However, as the disease progresses, individuals with Alzheimer’s generally forget that they cannot remember and so become unaware that anything is wrong with them.
Alzheimer’s Plus Aging
Because most people with Alzheimer’s are in their 60s, 70s, or 80s, the cognitive deficits observed in most individuals with this disease are really caused by Alzheimer’s tangles and plaques plus normal aging. This means that most individuals with Alzheimer’s disease have all of the memory problems described earlier in the section on normal aging, plus the additional problems that we will now describe.
Rapid Forgetting
The episodic memory deficit that is most characteristic of Alzheimer’s is rapid forgetting. That is, even when information is repeated while it is being learned, and even when hints and cues are given when it is trying to be retrieved, the memory cannot be reassembled—because the information is rapidly forgotten. This rapid forgetting is directly related to where Alzheimer’s disease strikes first and foremost—the inner part of the temporal lobe, including the hippocampus. Because the hippocampus and related structures are damaged, new memories for events will be impaired, new information will be learned with difficulty or not at all, and retrieval of memory for recent events and recently learned information will be impaired. Older, consolidated memories for events, however, can often be retrieved—although they will lack the vividness and subjective experience of a true episodic memory. See Chapter 4 and Part 2 for more information on these topics.
Rapid forgetting leads to several characteristic problems in daily life. Because they have difficulty remembering where they put things, individuals with Alzheimer’s often lose items such as their keys, glasses, wallet, purse, and mobile phone. Because they don’t recall conversations, individuals with Alzheimer’s frequently tell the same stories to the same people repeatedly, and they ask the same questions again and again and again—sometimes many times in an hour. Because they have difficulty recalling the route they have traveled and remembering landmarks while walking or driving, individuals with Alzheimer’s often get lost, even on familiar routes. As the disease progresses, they begin to lose track of the day, date, month, season, and year, because they cannot retain this information.
False Memories
False memories are common in individuals with Alzheimer’s disease. Sometimes it is simply a matter of believing a memory that occurred 30 years ago happened today—such as a conversation with a long-deceased parent. Or perhaps misremembering that they took their medications today when they took it yesterday. Sometimes the false memory may be more outlandish, such as combining events they heard on television with aspects of their own life. We have had patients tell us about a trip they took to an exotic country—only to later find out that they mixed their memory for a television program with that of a local day trip they took.
Word-Finding Difficulties
The semantic memory deficit that is most characteristic of Alzheimer’s disease is difficulty retrieving not only people’s names, but common, ordinary words used in everyday life, such as umbrella, closet, bookcase, and photograph. This impairment is so common and pervasive that family members typically get into the habit of jumping in to provide the missing word when their loved ones with the disease pause, searching for words. The semantic deficit in Alzheimer’s is more extensive than in normal aging because the damage from Alzheimer’s involves large portions of the outer part of the temporal lobe.
Habits and Routines Are Relatively Preserved
Procedural memory is fairly intact in mild Alzheimer’s disease. Habits and routines are therefore relatively preserved and can be used, to some extent, to compensate for episodic memory impairments. For example, if an individual with Alzheimer’s has difficulty remembering what is on the agenda for the day, rather than asking five times an hour they may be able to get into the habit of looking at a daily planner on the refrigerator, which they can do as often as they wish. Individuals with mild Alzheimer’s can also learn to routinely use memory aids, such as taking medications from a pillbox and writing things down in a notebook as soon as someone tells them something they need to remember, such as an appointment. Medications that increase the chemical acetylcholine in the brain can also help improve memory (for example, donepezil [Aricept]).
Vascular Cognitive Impairment and Vascular Dementia
A type of memory impairment with a different root cause is vascular cognitive impairment, the term used when memory and thinking are impaired due to strokes. If the impairment is severe enough to interfere with daily function, we use the term vascular dementia.
Most strokes occur when an artery sending blood from the heart to the brain becomes blocked off; that part of the brain doesn’t receive enough blood and dies. We used the word “vascular” to emphasize that the problem is with the blood vessels. Individuals are at risk for strokes if they are over age 55, have had prior strokes or stroke warning signs (called transient ischemic attacks or TIAs), were or are smokers, drink more than one alcoholic beverage per day, lead a sedentary lifestyle, eat an unhealthy diet, or have heart disease, diabetes, high cholesterol, high blood pressure, obesity, or disease in other blood vessels of the body.
Large strokes are generally noticeable to individuals and their family, as they may cause sudden loss of vision or speech, sudden weakness or numbness of an arm or a leg, or sudden impairment in coordination or walking. Small strokes, however, typically show no outward signs and are only noticeable over years as first dozens and then hundreds of them accumulate in the brain. Luckily, most strokes are small.
Damage to the Brain’s Wiring
Although strokes can literally affect any area of the brain, most affect the “white matter” that makes up the brain’s wiring—the connections between the brain cells—rather than the information-processing part of the brain cells. Because most of the wiring in the brain goes to and from the frontal lobes, vascular cognitive impairment causes frontal lobe dysfunction. Thinking is also generally slower, as brain processes have to work around roadblocks due to strokes.
Like Normal Aging—Only More So
Because vascular cognitive impairment tends to cause frontal lobe dysfunction, it leads to many of the same problems observed in normal aging, but to a greater extent. Working memory is diminished and it will be difficult for these individuals to keep information in their mind and manipulate it. Episodic memory problems include difficulty getting the desired information into memory, needing more effort to get the information out of memory, and frequently experiencing false and distorted memories.
Different Than Alzheimer’s Disease
Because the memory problems in vascular cognitive impairment are due to frontal lobe dysfunction, the memory loss manifests somewhat differently compared to that of Alzheimer’s disease. In general, there is no rapid forgetting. This means that in vascular cognitive impairment repetition will enable information to be learned. As orienting information, such as the date, is generally observed repeatedly during the day through newspapers, radio, television, and conversations, these individuals are usually oriented to the day, date, month, season, and year. They generally don’t repeat questions and stories. It is difficult for them to retrieve previously learned information spontaneously but—in contrast to Alzheimer’s—hints and cues help tremendously such that most information can be retrieved with the right cue. Although there are some difficulties retrieving semantic information, word-finding difficulties are less prominent compared to Alzheimer’s.
Procedural memory governing habits and routines may or may not be intact in vascular cognitive impairment depending on where the strokes are in the brain. Strokes often affect the basal ganglia and cerebellum, two of the key brain structures needed for procedural memory.
Frontotemporal Dementia
In behavioral variant frontotemporal dementia, the frontal lobes are directly damaged by pathology (of which there are many types). Marked changes in behavior and personality are the most prominent features, often including socially inappropriate behavior, loss of sympathy or empathy, compulsive or ritualistic behavior, and binge eating (particularly of sweets). Depending upon where in the frontal lobes the damage occurs, individuals with this disorder may show relatively normal memory or they may manifest all the problems described in patients with vascular cognitive impairment. When they have memory problems it tends to be difficult to improve them because individuals with this disorder generally refuse to believe that there is anything wrong with them. Instead, the family needs to adapt to them.
Normal Pressure Hydrocephalus
In normal pressure hydrocephalus (despite the name) there is a problem with the movement of spinal fluid in and around the brain such that the ventricular system inside the brain enlarges and pushes on the brain’s wiring that runs beside these expanding ventricles. This pressure can damage the wiring and produce memory problems similar to individuals with vascular cognitive impairment, in addition to incontinence and difficulty walking. The definitive treatment is with a tube to drain off some of the fluid.
Parkinson’s Disease, Parkinson’s Disease Dementia, and Dementia with Lewy Bodies
Individuals with Parkinson’s disease, Parkinson’s disease dementia, and dementia with Lewy bodies have a reduction of the chemical dopamine in the basal ganglia of the brain, which generally produces stiff and slow movements, tremor, and impairment in procedural memory. These individuals therefore experience difficulty in learning new skills, habits, and routines.
Frontal lobe function is also impaired when there is a loss of dopamine in the basal ganglia, and thus individuals with these disorders can manifest memory problems similar to those with vascular cognitive impairment.
Primary Progressive Aphasia and Semantic Dementia
Individuals with primary progressive aphasia have problems with language that interfere with their daily function. This disorder has several different variants, and difficulty accessing words from semantic memory is prominent in all of them. Individuals with the logopenic variant experience difficulty in retrieving common, ordinary words like hammock, vase, or blanket. Individuals with the non-fluent/agrammatic variant experience those word-finding difficulties plus halting, effortful speech that is missing other words as well. As discussed in Chapter 5, those with the semantic variant not only experience word-finding problems but may also lose what some words mean, such that given a specific word (such as “vase”) they may or may not be able to describe what its meaning is. Lastly, individuals with the related disorder of semantic dementia not only lose the meaning of some specific words but also lose the meaning of the items themselves such that they can no longer use them—as if they grew up in a culture that simply didn’t have hammocks or vases.
Looking for More Information?
Want to know more about these topics? Andrew and his colleague Maureen K. O’Connor have written two entire books on memory loss in normal aging, Alzheimer’s disease, and dementia. For individuals with mild memory problems, we recommend Seven Steps to Managing Your Aging Memory: What’s Normal, What’s Not, and What to Do About It.2 For individuals caring for their loved ones with dementia in the moderate or severe stages, we recommend Six Steps to Managing Alzheimer’s Disease and Dementia: A Guide for Families.3
Lastly, what about our 82-year-old accountant introduced at the beginning of the chapter? Although we cannot say she is aging normally without a proper evaluation, the problems she shared with us are not concerning. It is normal to walk into a room, become distracted by something else, and forget the reason why you are there. As mentioned earlier in this chapter, it is common for healthy older adults to have difficulty recalling people’s names. And if you multitask while driving you might very well end up in the wrong place and have no recollection of how you got there, because you are not paying enough attention to where you are going.
