Anomia In Normal Aging

Whereas there are clear-cut naming problems associated with old age, the term anomia may be even less appropriate to describe them than the naming problems of Alzheimer's disease, perhaps because they are so much more subtle than the naming problems of aphasia. Indeed the term "dysnomia" (here referring to a transient naming problem rather than a permanent disorder) may more accurately portray the naming problems of aging in that it implies a more fleeting problem rather than an enduring impairment. Phenomenologically, older adults report word-finding difficulties as they age (including more frequent tip-of-the-tongue experiences), and, in fact, laboratory-based studies have confirmed this report. In particular, older adults find the retrieval of proper names increasingly difficult. Whereas the literature confirms that proper nouns are particularly difficult with advanced age, difficulties with nouns and verbs are evidenced as well. There are some reports in the literature that noun retrieval is disproportionately impaired relative to verb retrieval with age, but more recent evidence suggests that, in carefully matched sets of nouns and verbs, the retrieval deficit associated with age, which becomes significant around age 70 years, is equivalent for both types of substantives.

Cross-sectional studies as a rule demonstrate significant naming problems for groups of older adults starting in the decade of the 70s. Longitudinal studies point to subtle declines in naming as early as the 40s. With normal aging, however, there is substantial variability across individuals within any given age cohort; some 80-year-olds perform like some 30-year-olds in a naming task. Education does seem to have long-term protective benefits in this regard. Results from the ability of older adults to rapidly choose a correct name on a multiple-choice task for items that they were unable to spontaneously retrieve, as well as being able to retrieve the correct name for an object once given a phonemic cue, suggest that the deficit in lexical retrieval for older adults lies in accessing the phonological shape of the target word. However, there is a suggestion that subtle semantic degradation may be involved as well from research examining the consistency of naming a given item over a series of test sessions.

Theoretical accounts for dysnomia in aging have centered around the well-described phenomenon of cognitive slowing. In particular, Burke and her colleagues have put forward an account of age-related naming deficits that combines cognitive slowing with the clear-cut deficit in accessing the phonological shape of a target word. Their model suggests that aging produces slowing, or "transmission deficits,'' across the board in the semantic and phonological networks that underlie lexical retrieval. The phonological system is relatively more affected, however, because, as activation spreads throughout the network, semantic activation for a particular target converges on the appropriate lexical node, but the activation must then diverge from the lexical node to the many phonological nodes that constitute the word. Because general slowing is at play in aging, the amount of activation that has accrued at the lexical node is less for older adults than for younger adults and, thus, when the activation spreads to the phonological nodes, it expires before crossing the threshold for word production.

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