One of the key concerns of older adults is the experience of memory loss, especially as it is one of the hallmark symptoms of Alzheimer's disease. However, memory loss is qualitatively different in normal aging from the kind of memory loss associated with a diagnosis of Alzheimer's (Budson & Price, 2005).
Recent research has identified a transitional state between the cognitive changes of normal aging and Alzheimer's disease (AD), known as mild cognitive impairment (MCI). Many people that experience mild cognitive impairment are at a high risk of developing Alzheimer’s disease. Several studies have indicated that MCI individuals are at an increased risk for developing AD, ranging from 1% to 25% per year; 24% of MCI patients progressed to AD in 2 years and 20% more over 3 years, whereas a recent study indicated that the progression of MCI subjects was 55% in 4.5 years (Almkvist & Arnáiz, 2003).
Memory decline in normal aging
The ability to encode new memories of events or facts and working memory shows decline in both cross-sectional and longitudinal studies (Hedden & Gabrieli, 2004). 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 (Nilsson, 2003). These deficits may be related to impairments seen in the ability to refresh recently processed information (Johnson et al., 2002). In addition, even when equated in memory for a particular item or fact, older adults tend to be worse at remembering the source of their information (Johnson, Hashtroudi, & Lindsay, 1993), a deficit that may be related to declines in the ability to bind information together in memory (Mitchell et al., 2000).
Domains of memory mostly spared
In contrast, implicit, or procedural memory typically shows no decline with age (Fleischman et al., 2004), short-term memory shows little decline (Nilsson, 2003) and semantic knowledge, such as vocabulary, actually improves somewhat with age (Verhaeghen, 2003). In addition, the enhancement seen in memory for emotional events is also maintained with age (Mather & Carstensen, 2005).
Retrospective versus prospective memory
Memory is involved in remembering to do things in the future, as well as in remembering what happened in the past. Some studies have found that older adults are worse at prospective memory than younger adults are, yet studies that examine prospective memory in naturalistic contexts often find that older adults are better than younger adults (Henry et al., 2004).
Most research on memory and aging has focused on how older adults perform less well at a particular memory task. However, recently researchers have also discovered that simply saying that older adults are doing the same thing, only less of it, is not always accurate. In some cases, older adults seem to be using different strategies than younger adults. For example, brain imaging studies have revealed that older adults are more likely to use both hemispheres when completing memory tasks than younger adults (Cabeza, 2002). In addition, older adults sometimes show a positivity effect when remembering information, which seems to be a result of the increased focus on regulating emotion seen with age (Mather & Carstensen, 2005). For instance, eye tracking reveals that older adults showed preferential looking toward happy faces and away from sad faces (Isaacowitz, Wadlinger, Goren & Wilson, 2006).
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