6.12: Aging of other Brain Functions

Memory

The process of consciously remembering information is referred to as memory. Memory is a very complicated process that is not well understood. Though certain areas of the brain, such as the hippocampus, (Figure 6.8 video) are especially important, many areas in the cerebral cortex and other brain regions act cooperatively to provide memory.

Memory can be divided into two broad types: short‑term memory and long‑term memory. Information that is stored in short‑term memory is retained for brief periods (seconds or minutes). The brain may be temporarily storing this information by continuously repeating the impulses containing the information, and the information is forgotten as soon as the impulses fade away. The information is also easily forgotten if a person is distracted by different information that sends other impulses through the neurons.

It is possible to increase the time information is stored in short‑term memory by keeping the impulses going. This can be done by repeating the stimulus over and over, just as a person can keep a wheel spinning by giving it a push now and then. This technique is used when people remember a telephone number for a short period by repeating it until the number is dialed.

Long‑term memory can store information for many years. For example, remembering an incident from childhood requires the use of long‑term memory. Apparently, information is stored in long‑term memory when impulses produce physical changes in the neurons processing the information. The more times impulses about an incident pass through the neurons, the greater the chances that they will cause the physical changes. This is why a person studies material over and over to remember it for a test.

Two types of changes are believed to occur in neurons that store information in long‑term memory. In one case, new molecules are produced in the neurons. Alternatively or additionally, the synapses in the nerve pathway are altered. In either case the impulses for the information travel much more easily. Then a small stimulus can trigger the neurons to produce the same impulses, resulting in the person consciously remembering the information.

Memory can also be classified according to the types of information stored. Incidental memory involves remembering information or skills that were self-taught. Procedural memory involves recalling how to perform a process or series of steps. Both types may include explicit memory and implicit memory. Explicit memory (declarative memory) involves remembering specific facts that a person tried to learn so they could be remembered. Implicit memory involves remembering specific facts that a person did not try intentionally to learn so they could be remembered. For example, a person may be unaware of learning procedures, processes, motor skills, or vocabulary by experience. Episodic memory involves recalling the times and places events happened. The events are mentally separated and oriented correctly regarding their proper time, sequence, and locations of occurrence. Working memory involves holding information at or close to the level of consciousness so it can be used in cognitive processing, such as solving a problem or planning a complex activity.

Aging causes a decline in short‑term memory in most people. The rate of decline varies highly between individuals. This may be due in part to differences in the rate of age changes within the nervous system, but it is caused by other factors to a greater degree. These factors include differences in general health, diet, presence of specific diseases, past patterns of mental activity, motivation, and diverse psychological, social, and economic parameters. So many features affect memory that it is impossible to predict which changes have occurred or will occur in a particular individual.

On the average, the decline in short‑term memory is gradual and slow until approximately age 60 and then becomes ever more rapid, especially after age 70. However, the total amount of loss in memory functioning in a normal individual is relatively slight regardless of age. In many cases changes in memory can be noticed only in carefully controlled experimental situations, and because people develop compensatory strategies, such age changes usually do not affect ordinary activities significantly.

The greatest decline in short‑term memory occurs for information that is presented quickly and verbally. Information about completely unfamiliar things also becomes much harder to remember. Older people have more difficulty recalling information than simply recognizing it. For example, questions that require an older person to supply the answer are harder than those which require the person to select the correct answer from among several incorrect ones. To help elderly people remember, information should be presented slowly, in an organized manner, using relevant and concrete examples and visual aids. People are better able to recall information when cues such as notes and mnemonic devices are used and when they are allotted additional time to study and respond. It is also helpful to make adjustments to compensate for deficits in vision and hearing.

The reasons for the decline in short‑term memory are not understood but may include age changes in the number of neurons, the number or structure of synapses, and the amounts of different neurotransmitters present in memory pathways.

Long‑term memory seems to be largely unaffected or to improve as people get older.

Age changes in incidental memory and procedural memory depend upon whether they use explicit memory or implicit memory. Explicit memory decreases with aging, especially when the facts had to be learned quickly or they must be remembered quickly. Aging has much less effect on explicit memory when more time is used to learn or to remember facts. Implicit memory shows little decline when elders unknowingly experience or are given prompts related to the passed information, such as being placed in a familiar setting. Implicit memory shows the greatest age-related decline when a person tries intentionally to remember. Because of different age-related changes in these two types of memory, elders largely retain their ability to perform even complex procedures they have practiced, but they may have difficulty explaining how to carry them out. Episodic memory also decreases with age. Failure of episodic memory results in erroneously remembering widely separate events as having occurred together or being unable to connect related events.

Working memory decreases with aging. Therefore, while the ability to remember specific information does not decline much, the ability to use multiple pieces of information in complex cognitive activity declines significantly. This may result from age-related reductions in effectively selecting, retrieving, and processing information consciously.

Elders can increase their memory functions through educational and training programs about memory. Memory training programs may emphasize specific memory techniques. Examples of such techniques include using written notes; mentally repeating information often; organizing material into large meaningful blocks rather than many unrelated details; making up sentences or words where letters (e.g., first letter in each word, letters of the words) stand for the items being remembered; mentally picturing information, images, or processes; putting information into a story, rhyme, or song; sketching pictures or diagrams; finding experiences in life that are relevant or related to the information. Factors that help learning information include studying when energy levels are high, but not after eating a large meal; avoiding large quantities of aspartame artificial sweetener (e.g., diet beverages); avoiding distractions when learning; getting restful REM sleep.

Other memory training programs take less direct approaches. Sometimes using cognitive restructuring to promote positive expectations in memory performance produces greater and more lasting beneficial effects on memory. This may result from using practical techniques in only similar situations, while cognitive restructuring techniques are often used in diverse situations.

Knowledge of the associations between memory and aging are important for improving outcomes from training programs for elders. For example, modifying job training programs to accommodate age changes in memory becomes more important as the numbers and ages of older workers increase.

Thinking

Like conscious memory, thinking occurs entirely within the brain, but it is an even more complicated and less well understood process. Thinking includes problem solving, planning, and other activities that may be called intelligence. Intelligence may be divided into two categories. Crystallized intelligence involves using cognitive skills with familiar learned activities. Fluid intelligence involves using cognitive skills in new situations. Examples of fluid intelligence include learning novel problem solving, motor activities, or reasoning. It involves more flexibility in dealing with situations. No attempt will be made here to explain how the brain performs thinking.

Age Changes in Thinking

As with age changes in short‑term memory, there is on the average a slow and gradual decline in thinking to approximately age 60; the rate of decline increases more each year after that, especially after age 70. Note, however, that the loss of thinking ability is relatively slight regardless of age and that changes can be noticed only through careful testing. The small amount of change, coupled with the use of compensatory strategies, usually means that there is not a significant effect on ordinary normal activities. There is much variability among individuals in regard to age‑related changes in thinking because of variations in aging of the nervous system and differences in other factors that affect thinking. As a result, no one can anticipate how aging will affect an individual's ability to think. Some individuals show no changes in thinking, and up to 10 percent of older people show an increase in thinking ability. This increase seems to be due to continued use of thinking, ongoing education, or good economic status. Among those whose thinking declines with aging, thinking becomes slower and changing one's train of thought becomes more difficult.

Aging has little effect on crystallized intelligence, and many people show age-related increases. Fluid intelligence usually shows age-related decreases. Men show earlier decline in crystallized intelligence; women show earlier decline in fluid intelligence. Deterioration in the ability to solve problems and make decisions quickly and accurately is most evident when these processes require the consideration of many factors.

Vocabulary and conversation

Language functions rely heavily upon memory and intelligence. There is little or no age-related change in knowing the meanings of words, though vocabulary may increase throughout life. Age-related changes in conversation include using more short and simple sentences; sentence fragments; pronouns and less specific terms; vague adjectives; vague references to time and place. Working vocabulary, ability to find the right word, and adherence to one topic decline. These changes increase as background distractions increase (e.g., noise, motion). Comprehension of conversations decreases as the content of a conversation becomes more complex; more disjointed; more novel; faster; and with increased distractions. These age-related changes usually do not prevent elders from carrying on meaningful conversations. The changes seem to result from age-related changes in memory and in cognition, including changes in methods of processing verbal information.

Supporting memory and intelligence

Factors that reduce age-related decreases in memory and intelligence and often improve these functions include good health; exercise; passed and continuing education; activities requiring complex mental functions; self-determination and self-direction; and a sense of self-efficacy. Estrogen therapy in postmenopausal women improves some aspects of memory and cognition including short term verbal memory, abstract reasoning, logical thinking, and overall cognitive functioning. Using proper prevention, intervention, and cognitive training programs for elders help to sustain and improve memory and intelligence as age increases.

Personality

Personality includes many facets, including levels of anxiety, depression, self‑consciousness, vulnerability, impulsiveness, hostility, warmth, assertiveness, gregariousness, and emotions.

Age Changes in Personality

Personality undergoes changes up to about 30 years of age, after which most of its aspects are extremely stable. However, major upsetting events in a person's life, such as a major illness, may significantly alter one's personality.

Personality greatly influences the choices made throughout life, particularly in matters related to education, exercise, diet, and health care. All these parameters influence the length and quality of life. Also, personality is a major determinant of an individual's ability to adapt to changing circumstances. Since personality becomes stable, the nature of its contribution to the ability to adjust remains about the same throughout life. Therefore, knowledge of personality can be useful in predicting an individual's future ability to adapt to the new life situations that develop with aging.

Sleep

The effects of aging on sleep are of great interest. One reason for this is the perception that older individuals are sleepier during the day. Second, there is evidence that compared with wakeful (daytime) values, body functions are different during sleep and at night. To fully understand aging, the body must be studied in the sleeping as well as the wakeful state.

Age Changes in Sleep

As people get older, several changes in sleep usually occur. Complaints about sleep difficulties rise from 15 percent among young adults to almost 40 percent among elders. With aging, more time is needed to fall asleep, there are more awakenings during the night, and wakeful periods are longer. Reasons for the increased number of awakenings include a higher incidence of indigestion, pain (e.g., arthritis), rhythmic leg movements, sleep apnea, and circulatory problems (e.g., irregular heartbeat). Some individuals have more awakenings because a decline in the capacity of the urinary bladder requires them to void urine more often. The rise in the level of norepinephrine may also contribute since norepinephrine increases alertness. The increase in awakenings is greater in men than in women. Even though sleep becomes more fragmented, the total amount of time spent asleep in each 24‑hour period remains about the same because more time is spent in bed as age increases.

Changes occur in the type of sleep as well as in its continuity. While there is increasing variability among people as they get older, there is an average increase in the time spent in stage 1 sleep, the least restful of the five types. The existence and significance of age changes in amounts of stage 2 and stage 3 sleep are uncertain.

While asleep, people switch between stage 4 sleep and rapid eye movement (REM) sleep every 80 to 100 minutes. These are the most restful stages of sleep. There is an age‑related decline in the amounts of time spent in stage 4 sleep and REM sleep, although the decrease in REM sleep becomes substantial only in very old age.

It is difficult to determine how much or which of the changes in sleep are due to aging of the brain and which are due to other age‑related factors, such as having diseases, taking more medication, being past menopause, having different daily routines because of retirement, having more freedom for daytime napping, and experiencing altered social situations such as death of a spouse or a move to a different home or institution.

Sleep can be improved by keeping to a schedule; adhering to bedtime routine; creating an environment conducive to sleep (e.g., quiet, dark); exercise; treating medical problems and sleep apnea; entraining circadian rhythms with bright light therapy; biofeedback training; and mental relaxation techniques. Things to avoid include daytime naps; stimulants (e.g., caffeine) late in the day; strenuous activity shortly before bed; using the bed and bedroom for work, worrying, or solving problems; medications that adversely affect sleep (e.g., diuretics at bedtime); and chronic use of sedatives, hypnotics, and other sleep inducers;

The effects of age‑related changes in sleep include a reduction in the quality of sleep and alterations in the time when it occurs during each 24‑hour period. These effects probably explain why more people feel sleepy during the day as they get older. However, this is not a normal part of aging. When daytime sleepiness interferes with regular activities, it should be considered abnormal and warrants further diagnosis. The presence of age‑related increases in abnormal sleepiness has contributed to the stereotype of the older person who nods or falls asleep at inappropriate times.