Normal versus Abnormal Memory Aging
Many normative changes take place in memory as people grow old, such as those in working memory and secondary memory. Still, many aspects of memory functioning do not change, such as the ability to remember the gist of a story. Increasingly forgetting names or what one needs at the supermarket, though annoying, appears to be part of aging. However, some people experience far greater changes, such as forgetting where they live or their spouse’s name. Where is the line dividing normative memory changes from abnormal ones?
From a functional perspective, one way to distinguish normal and abnormal changes is to ask whether the changes disrupt a person’s ability to perform daily living tasks. The normative changes we have encountered in this chapter usually do not interfere with a person’s ability to function in everyday life. When problems appear, however, it would be appropriate to find out what is the matter. For example, a person who repeatedly forgets to turn off the stove or forgets how to get home is clearly experiencing changes that affect personal safety
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and interfere with his or her daily life. Such changes should be brought to the attention of a physician or psychologist.
As indicated in Chapter 2, recent advances in neuroscience, especially the study of brain-behavior relations, has led to an explosion in our knowledge of specific diseases and brain changes that can create abnormal memory performance. For example, researchers can test for specific problems in visual and verbal memory through neuroimaging by examining glucose metabolism with PET scans and fMRIs (Prull et al., 2000). Such brain-imaging techniques also allow researchers to find tumors, strokes, and other types of damage or disease that could account for poorer-than-expected memory performance. Certain changes in brain wave patterns in the medial-temporal lobe of the brain are indicative of decrements during encoding and retrieval of verbal information (Gabrieli, Brewer, Desmond, & Glover, 1997; Tulving, Markowitsch, Kapur, Habib, & Houlse, 1994). Finally, significantly poorer-than – normal performance on neuropsychological tests of memory are also useful in establishing that the memory changes observed are indeed abnormal (Prull et al., 2000).
Some diseases, especially the dementias, are marked by massive changes in memory. For example, Alzheimer’s disease involves the progressive destruction of memory beginning with recent memory and eventually including the most personal— self-identity. Wernicke-Korsakoff syndrome involves major loss of recent memory and sometimes a total inability to form new memories after a certain point in time.
The most important point to keep in mind is that telling the difference between normal and abnormal memory aging, and in turn between memory and other cognitive problems, is often very difficult (Fisher, Plassman, Heeringa, & Langa, 2008; Prull et al., 2000). There is no magic number of times someone must forget something before getting concerned. Because serious memory problems can also be due to underlying mental or physical health problems, these must be thoroughly checked out in conjunction with obtaining a complete memory assessment.
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Memory and Mental Health
Several psychological disorders involve distorted thought processes, which sometimes result in serious memory problems. The two disorders that have been the main focus of research are depression (Lockwood et al., 2002; Watts, 1995) and the dementias (Brandt & Rich, 1995); but other disorders, such as amnesia following a head injury or brain disease, are also important (O’Connor, Verfaellie, & Cermak,
1995) . Depression is characterized by feelings of helplessness and hopelessness (American Psychiatric Association, 1994). Dementia, such as Alzheimer’s disease, involves substantial declines in cognitive performance that may be irreversible and untreatable (Mattson, 2004). Much of the research on clinical memory testing is on differentiating the changes in memory due to depression from those involved in Alzheimer’s disease.
Serious depression impairs memory (Backman, Small, & Wahlin, 2000; Gotlib, Roberts, & Gilboa, 1996; Luszcz & Lane, 2008). For example, severely depressed people show a decreased ability to learn and recall new information (Lockwood et al., 2000,
2002) ; a tendency to leave out important information (McAllister, 1981); a decreased ability to organize (Backman & Forwell, 1994); less effective memory strategies (de Frias et al., 2003); an increased sensitivity to sad memories (Kelley, 1986); and decreased psychomotor speed (La Rue, Swan, & Carmelli, 1995).
An interesting finding emerges from the literature when age-related differences in the effects of depression on memory are considered. Two studies have found that the negative effects of depression on memory are greater in young and middle-aged adults than in older adults (Burt, Zembar, & Niederehe, 1995; Kindermann & Brown, 1997). This suggests that the effect of depression on memory may decrease gradually as we grow older, and even more so in very old age (Backman, Hassing, Forsell, & Viitanen, 1996). It may be that once normative age differences in episodic memory are eliminated statistically, few differences between depressed and nondepressed elderly remain. Thus, at this point the memory impairments that accompany severe depression appear to be equivalent across adulthood.
However, much more research needs to be done before we have a clear picture. Additionally, we need to know more about the possible effects of mild and moderate levels of depression.
Alzheimer’s disease is characterized by severe and pervasive memory impairment that is progressive and irreversible (Mattson, 2004; Spaan et al.,
2003) . The memory decrements in Alzheimer’s disease involve the entire memory system, from sensory to long-term to remote memory. The changes that occur early in Alzheimer’s disease are very similar to those that occur in depression. However, because depression is treatable and Alzheimer’s disease is not, clinicians must differentiate the two. This differentiation is the underlying reason for the major effort to develop sensitive and comprehensive batteries of memory tests (Rentz et al., 2004).
Memory, Nutrition, and Drugs
Researchers and clinicians often overlook nutrition as a cause of memory failures in later life (Perlmutter et al., 1987). Unfortunately, we know very little about how particular nutrient deficiencies relate to specific aspects of memory. In a recent study of widely marketed and purported memory enhancers, more solid findings were limited to studies with animals. For example, phosphatidylserine (PS) attenuated neuronal deterioration effects of aging and restored normal memory on a variety of tasks in rodents (McDaniel et al., 2002). Preliminary findings with humans are limited. In fact, studies have failed to show this relationship for older adults with probable Alzheimer’s disease. However, for older adults with moderate cognitive impairment, PS did show modest increases in memory.
Likewise, many drugs have been associated with memory problems. The most widely known of these are alcohol and caffeine, which if abused over a long period are associated with severe memory loss (Ryan et al., 2002; Schinka et al., 2003). Less well known are the effects of prescription and over-the- counter medications. For example, sedatives and tranquilizers have been found to impair memory performance (Block, DeVoe, Stanley, Stanley, & Pomara, 1985).
These data indicate that it is important to consider older adults’ diets and medications when assessing their memory performance. What may appear to be serious decrements in functioning may, in fact, be induced by poor nutrition or specific medications. Too often, researchers and clinicians fail to inquire about eating habits and the medications people take. Adequate assessment is essential to avoid diagnostic errors.
1. From a functional perspective, how does one tell the difference between normal and abnormal memory aging?
2. How does severe depression affect memory?
3. How do alcohol and nutrients affect memory?
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