Loss of Semantic Associative Categories in Patients with Alzheimer's Disease

Abstract

Deterioration of semantic memory is one of the primary neuropsychological deficits caused by Alzheimer's disease (AD). In this study, we hypothesize that the breakdown of semantic memory in the mild-to-moderate stage of AD is due to the disruption of the semantic network that links the concepts. Furthermore, the loss of these links is not homogeneous through the semantic association categories (i.e., Superordinate, Contiguity, Part/Whole, Attribute, Function). Twenty-two subjects (11 patients with mild-to-moderate dementia and 11 control subjects matched on demographics) participated in the study. Both controls and patients with AD underwent extensive neuropsychological evaluation and three experimental tasks: (1) Naming Task, (2) Semantic Association Task, and (3) Semantic Knowledge Task. Results showed that: (1) The AD group was significantly different from the normal controls group in all the experimental tasks; (2) the Semantic Association Task was significantly worse than the other tasks; (3) for the AD group, the scores of the Function and Part/Whole association categories were higher than in the other categories; and (4) living stimuli were more impaired than nonliving. These data confirm prior research showing the semantic association is differently impaired in AD patients.

Deterioration of semantic associative relationships in mild cognitive impairment and Alzheimer Disease

“…This finding is in line with other previous findings (Di Giacomo, De Federicis, Pistelli, et al, 2012;Passafiume et al, 2012), which showed that the semantic impairment in AD starts with difficulty in using the semantic associative relationships and not with a deficit in naming of the concepts.…”

Does Mount Vesuvius Indicate an Outbreak of Alzheimer's Disease?

“…Analyses revealed a positive correlation between the volcano item score and the category fluency test score in the group with AD. These findings suggest that lower semantic proximity in naming a specific object reflects the degree of semantic network deterioration in AD . Moreover, the findings argue for a top‐down deterioration beginning with the loss of higher‐order categories.…”

Evaluating the effects of episodic and semantic memory induction procedures on divergent thinking in younger and older adults

“…One possible explanation for the present findings is drawn from research into the maintenance of verbal proficiencies in older adults, such as vocabulary, word comprehension and verbal working memory. It has been found that older adults are significantly better than young adults in verbal divergent thinking tasks, whereas the opposite is true for visual divergent thinking tasks [129]. It is therefore reasonable to postulate that verbal divergent thinking in older adults may be supported by the verbal proficiencies that remain intact across the lifespan [12].…”