5/26/17: NORMAL COGNITIVE AGING: Slowing Down, Losing Focus and Processing Speed, But Still Functioning Well

My smart, intellectual brother complained on his 60th birthday last Sunday that his memory, which has always been superb, had gone to hell. I asked him to give me some examples of his forgetfulness, and what he came up with fit neatly into the category of normal cognitive aging.

Example: He couldn’t remember the name for the practice in which minorities are given a preference in college admissions. All he could remember was “AA.”

Memory involves a number of neural tasks—one of which is retrieving stored information—that are influenced by your attentional ability, which is, in turn, determined by other skills. Having problems with recalling someone’s name is a very common memory “gap” as we age. It is known as the tip-of-the-tongue phenomenon. (See below.)

In recent blog posts, I’ve discussed cognitive deficits, in particular, memory decline. To round out the subject, I’m going to look at normal age-related memory changes and other cognitive adjustments. I’ve shared some of this material before on my Facebook page. On 7/8/16, I blogged about tests of cognition, including the MMSE (Mini-Mental State Examination). The following is an edited excerpt from my book, “Our Parents in Crisis,” with the citations omitted:

**

There is no question that as we age, our thinking slows down. Cognitive decline is natural, but its extent varies among individuals and among the cognitive functions that we perform. Decline should not be assumed; but neither should it be denied.

According to Ronald C. Petersen, M.D., director of the Mayo Alzheimer’s Disease Research Center in Rochester, Minn., most people undergo a gradual cognitive decline over their lifetime, typically with regard to memory. This slowdown is minor and may be annoying, but it doesn’t compromise your ability to function. Only one in 100 people, says Petersen, experiences “virtually” no decline. . . .

Intelligence

It is important to understand that intelligence is not the same as cognitive function, but intelligence does figure into cognitive aging.

According to “Brocklehurst’s Textbook of Geriatric Medicine & Gerontology” (Brocklehurst), an intelligence quotient (IQ) is a “derived score used in many test batteries designed to measure a hypothesized general ability.” So-called “general intelligence,” explain Brocklehurst contributors, Drs. Jane Martin and Michelle Gorenstein, can be thought of as our “overall ability on all types of intellectual tasks.”

General intelligence is subdivided into fluid intelligence, which measures the “degree to which an individual can solve novel problems without any previous training,” Martin and Gorenstein explain, and crystallized intelligence, which is the amount of knowledge and information that a person brings to a testing situation.

Fluid intelligence [problem-solving] eventually plateaus and declines with normal aging—between ages 49 and 92, according to studies—whereas crystallized intelligence [knowledge], which increases from childhood into late adulthood, does not. Thus, an older person will have the benefit of youthful intellectual activities and educational pursuits—including school-based knowledge, vocabulary, and reading ability—to apply to a standardized cognitive test or an everyday cognitive challenge.

Cognitive Reserve

Research strongly suggests that a person who possessed high childhood mental ability and engaged in intellectually demanding tasks and experiences as a child will show less cognitive decline with age than a person who did not. Such a person has a “cognitive reserve” that will buffer the loss when cognitive impairment occurs. The longtime pursuit of an active, socially engaged lifestyle also purportedly adds to this hypothetical reserve.

According to Martin and Gorenstein, the cognitive-reserve model suggests “that the brain actively attempts to compensate for the challenge represented by brain disease and hypothesizes that adults with higher initial cognitive ability are better able to compensate for the effects of aging and dementia.”

Experts theorize that only after this reserve is depleted does an underlying impairment become apparent. People with brain pathology [damage] who have a superior cognitive reserve seem to compensate better than those whose impairment is of a similar degree, but who lack a strong early educational and intellectual foundation.

Cognitive reserve is not the same as the “use-it-or-lose-it” hypothesis, which proposes that elders can slow the rate of age-related cognitive decline by engaging in mentally stimulating exercises. Although studies suggest that lifelong intellectual activities bolster old-age cognitive performance, use-it-or-lose-it is more of an “optimistic hope than an empirical reality,” according to psychology Professor Timothy A. Salthouse, who is director of the Cognitive Aging Laboratory at the University of Virginia.

Cognitive Domains

Neuropsychiatric experts categorize cognitive functions by domain, which you may conceptualize as a realm of thinking. While each domain is distinctive, functional overlap exists among them and their respective operations.  Memory, for example, consists of encoding, storing, and retrieving information, neural tasks that are influenced by our attentional ability, which involves both focus and concentration and the speed at which our brains can process information.

Experts base their understanding of how aging affects cognitive domains on studies of elders’ performances on standardized intelligence and neuropsychological tests. Before cognitive profiles of older subjects can be compiled, they must take multiple tests of a given function. Because the scoring and evaluation of such tests can be tricky—at the very least, confounding factors such as fatigue, stress, and medication use must be considered—our understanding of cognitive aging lacks what you might call rock-solid conclusions. But you can count on some generalities.

The most important domain functions are:

·        Attention

Attention, according to the Brocklehurst authors, “is a complex process that allows one to filter stimuli from the environment, hold and manipulate information, and respond appropriately.” It relates to your ability to focus and concentrate on a particular stimulus for a sustained time period.

Tests show that the effects of aging on a person’s attention depend upon the complexity of the task presented. Even the oldest old can maintain attention for simple tasks, such as hearing and repeating a telephone number; but when tasks require older people to divide their attention, they tend to respond more slowly and make more errors. …

In general, normal aging causes a decline in sustained and selective attention—the latter of which requires screening out interference, such as a television—and an increase in distractibility. Intact attention is a prerequisite for healthy memory function.

·        Processing Speed

Processing speed is the rate at which you can process information. It, therefore, determines the amount of information that your brain can process at a given time.

Processing speed definitely declines with age and may account in large part for deterioration in memory and other cognitive processes, such as the executive functions (below). Not only does an elder’s thinking slow, but his or her working memory no longer commands the same amount of information that it once could. . . .

According to Martin and Gorenstein, slower processing speed unquestionably accounts for the age-associated decline in fluid-intelligence ability, which includes both memory and spatial aptitude, the latter being your ability to perceive spatial relationships, such as between objects. Slower processing speed does not affect crystallized-intelligence ability, which controls verbal skills.

·        Verbal Abilities

 Most verbal abilities remain preserved with normal aging.

The two verbal-skill areas that receive the most attention and testing in the older population are verbal fluency, which is the ability to retrieve words based on their meaning or their sounds (semantic and phonemic); and confrontation naming, the ability to identify an object by its name.

Elders may experience a slight natural decline in verbal fluency. In a typical test of this ability, an older subject must generate within a defined time period as many words as he possibly can that begin with a specific letter: Dog, doll, dart, dagger . . . You can see how memory would be implicated in such a test, too.

The tip-of-the-tongue or TOT phenomenon, which occurs when you know the name of a person or an object, but can’t retrieve it, commonly affects the confrontation-naming ability. Older adults have significantly more TOT experiences than younger adults for proper nouns and difficult words. This is normal.  

·        Executive Functions

Executive functions involve higher-order mental processes. According to Drs. Martin and Gorenstein, these functions “describe a wide range of abilities that relate to the capacity to respond to a novel situation.” They involve:

§         Planning

§         Decision-making

§         Abstract thinking

§         Initiating and inhibiting actions

§         Monitoring and changing behavior

§         Anticipating outcomes and adapting

§         Troubleshooting

Your cerebral cortex is largely responsible for your higher brain functions, such as reasoning and memory. It forms the extensive surface layer of your cerebrum, which is what we tend to think of as the whole brain. The cerebral cortex is composed primarily of nerve-cell bodies and unmyelinated fibers and, because of its color, is called gray matter.

Your cerebrum is divided into two symmetrical halves called hemispheres, which are designated left and right. Each hemisphere, in turn, is divided into four lobes that are named for the skull bones overlying them: the frontal, parietal, occipital, and temporal. Because the brain-control center for the executive abilities is located in the prefrontal cortex, which occupies part of each hemisphere’s frontal lobe, executive function is alternately known as frontal-lobe function.

The cerebrum encompasses all of the parts within your skull except your cerebellum (Latin for little brain), medulla oblongata, and pons. The cerebellum lies below the occipital lobes, which are in the posterior of the two hemispheres, and is responsible for the regulation and coordination of complex voluntary muscular movement and the maintenance of posture and balance. The medulla oblongata and pons make up the brain stem; the pons connects the cerebellum to the stem.

You need not know brain anatomy to know that normal aging is generally associated with a decline in executive functioning. This decline varies considerably from one person to the next, however, and fluid intelligence plays a part.

·        Memory

Your memory function erodes as you age, but research suggests that overall cognitive slowing, which includes reduced processing speed and slower information-retrieval time, and changes in attentional ability largely determine the extent of this erosion.

We laypeople typically distinguish short-term and long-term memory incorrectly, defining them as the recent past and the long-ago past, respectively.

Neuropsychological experts who test memory view short-term or, more precisely, working memory as the storage of encoded items for a few seconds up to two minutes. It is a temporary holding cell for information that our brains process and encode into long-term memory for later recall. To evaluate a patient’s short-term recall, a test-giver may name three unrelated objects—a lamp, a cat, a turnip—and ask the patient to repeat the objects after just a few minutes have passed.

Contrary to popular belief, long-term memory is not just the ability to recall past events and learned information. It also includes the ability to remember upcoming events, such as an appointment, and to keep track of information in the present, such as a conversation or a book you’re reading.

Normal age-associated memory regression or forgetfulness is usually minor and can be aggravating—misplacing keys or eyeglasses, for example—but it does not compromise an elder’s ability to manage daily activities. He or she still can prepare dinner, engage coherently in a conversation, shop for clothes, and do much more, independently and reliably. In evaluating cognitive impairment, independence is key.

Ann, 5/26/17  

 

Meetingforgetfulness

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