Memory and Aging - Memory Decline in Normal Aging

Memory Decline in Normal Aging

Normal aging is associated with a decline in various memory abilities in many cognitive tasks; the phenomenon is known as age-related memory impairment (AMI) or age-associated memory impairment (AAMI). The ability to encode new memories of events or facts and working memory shows decline in both cross-sectional and longitudinal studies. Studies comparing the effects of aging on episodic memory, semantic memory, short-term memory and priming find that episodic memory is especially impaired in normal aging; some types of short-term memory are also impaired. The deficits may be related to impairments seen in the ability to refresh recently processed information. Source information is one type of episodic memory that suffers with old age; this kind of knowledge includes where and when the person learned the information. Knowing the source and context of information can be extremely important in daily decision-making, so this is one way in which memory decline can affect the lives of the elderly. Therefore, reliance on political stereotypes is one way to use their knowledge about the sources when making judgments, and the use of metacognitive knowledge gains importance. This deficit may be related to declines in the ability to bind information together in memory during encoding and retrieve those associations at a later time.

Episodic memory is supported by networks spanning frontal, temporal, and parietal lobes. The interconnections in the lobes are presumed to enable distinct aspects of memory, whereas the effects of gray matter lesions have been extensively studied, less is known about the interconnecting fiber tracts. In aging, degradation of white matter structure has emerged as an important general factor, further focusing attention on the critical white matter connections.

In particular, associative learning, which is another type of episodic memory, is vulnerable to the effects of aging, and this has been demonstrated across various study paradigms. This has been explained by the Associative Deficit Hypothesis (ADH), which states that aging is associated with a deficiency in creating and retrieving links between single units of information. This can include knowledge about context, events or items. The ability to bind pieces of information together with their episodic context in a coherent whole has been reduced in the elderly population. Furthermore, the older adults’ performances in free recall involved temporal contiguity to a lesser extent than for younger people, indicating that associations regarding contiguity become weaker with age.

Several reasons have been speculated as to why older adults use less effective encoding and retrieval strategies as they age. The first is the “disuse” view, which states that memory strategies are used less by older adults as they move further away from the educational system. Second is the “diminished attentional capacity” hypothesis, which means that older people engage less in self-initiated encoding due to reduced attentional capacity. The third reason is the “memory self-efficacy,” which indicates that older people do not have confidence in their own memory performances, leading to poor consequences. It is known that patients with Alzheimer’s disease and patients with semantic dementia both exhibit difficulty in tasks that involve picture naming and category fluency. This is tied to damage to their semantic network, which stores knowledge of meanings and understandings.

One phenomenon, known as "Senior Moments", is a memory deficit that appears to have a biological cause. When an older adult is interrupted while completing a task, it is likely that the original task at hand can be forgotten. Studies have shown that the brain of an older adult does not have the ability to re-engage after an interruption and continues to focus on the particular interruption unlike that of a younger brain. This inability to multi-task is normal with aging and is expected to become more apparent with the increase of older generations remaining in the work field.

A biological explanation for memory deficits in aging includes a postmortem examination of five brains of elderly people with better memory than average. These people are called the "super aged,” and it was found that these individuals had fewer fiber-like tangles of tau protein than in typical elderly brains. However, a similar amount of amyloid plaque was found.

More recent research has extended established findings of age related decline in executive functioning ., by examining related cognitive processes that underlie healthy older adults’ sequential performance. Sequential performance refers to the execution of a series steps needed to complete a routine, such as the steps required to make a cup of coffee or drive a car. An important part of healthy aging involves older adults’ use of memory and inhibitory processes to carry out daily activities in a fixed order without forgetting the sequence of steps that were just completed while remembering the next step in the sequence. A recent study examined how young and older adults differ in the underlying representation of a sequence of tasks and their efficiency at retrieving the information needed to complete their routine. Findings from this study revealed that when older and young adults had to remember a sequence of 8 animal images arranged in a fixed order, both age groups spontaneously used the organizational strategy of chunking to facilitate retrieval of information. However, older adults were slower at accessing each chunk compared to younger adults, and were better able to benefit from the use memory aids, such as verbal rehearsal to remember the order of the fixed sequence. Results from this study suggest that there are age differences in memory and inhibitory processes that affect people’s sequence of actions and the use of memory aids could facilitate the retrieval of information in older age.