The loss of conceptual associations in mild Alzheimer's dementia

Abstract

Changes in semantic memory are a controversial topic in research on cognitive decline in aging. In this study, we analyzed whether the semantic deficits in mild Alzheimer's disease (AD) reflect the information acquisition process, and whether the deficits are related to when the information was initially stored. We hypothesized that in the earlier stages of dementia, the ability to access semantic associative relations reflects the use of these associations during different developmental stages. Specifically, we asserted that Alzheimer's patients might be able to access the relations that are learned earlier in life for the longest amount of time compared to those that are learned later. In this study, 254 subjects were divided into four groups (child, adult, senior, and Alzheimer's patients groups) and were evaluated with an experimental semantic association task that incorporated five semantic associative relations that were used to compare performance by age group. An analysis of variance (ANOVA) 4 × 5 test showed a significant main group effect, F(3, 250) = 97.1, p < .001, and an associative relations effect, F(4, 1000) = 23.1, p < .001, as well as an interaction of Group × Associative Relations, F(12, 1000) = 8.5, p < .001. The results demonstrated that the semantic associative relations that were acquired in later developmental stages were less preserved in persons with mild AD (i.e., superordinate relation, p < .0001). On the contrary, the semantic relations acquired earlier in childhood were better preserved in persons with mild AD. Our results suggest that semantic impairment begins with difficulties in using the associative relations that link concepts together in the semantic memory of patients with mild AD dementia (and possibly in individuals with mild cognitive impairment).

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.…”

“…It seems that the associative relationships elicited by visuoperceptual stimuli support the associative semantic ability when the breakdown of the verbally mediated semantic associative relationships occurs. This hypothesis is coherent with the idea that the deterioration of the semantic network is reverse to the acquisition of the semantic associative relationships in childhood (Di Giacomo, De Federicis, Pistelli, et al, 2012).…”

“…The SAT has been extensively described elsewhere (Di Giacomo, De Federicis, Pistelli, et al, 2012). It is composed of 180 items, balanced between living and nonliving items and distributed across four associative relations: superordinate, contiguity, part/whole, and function.…”

“…In patients with AD, associative relations based on links that require verbal support for meaningful association deteriorate faster than those relations that are based on perceptual and functional features . These patterns of deterioration mirror the acquisition of semantic associative networks in life-span development (Di Giacomo, De Federicis, Pistelli, et al, 2012).…”

Dissociating Normal Aging from Alzheimer’s Disease: A View from Cognitive Neuroscience

“…Due to the degeneration of semantic networks, AD patients have restricted access to semantic memory content [151–153]. As a consequence, they typically show poor performances in naming tasks that require the identification of objects.…”