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.

Key words:

• Alzheimer's disease
• semantic categories
• semantic memory

ACKNOWLEDGEMENT

This study was supported by two grants—one part in the Italian Public Health Department Grant, 2007; another part in the Italian Ministerial Grant Funds for Investment in Basic Research (FIRB)–Future in Research, 2008.

We have to thank very much Professor Lisa Morrow, from Western Psychiatric Institute and Clinic at the University of Pittsburgh, PA, for her valuable suggestions and for her assistance in the preparation of this article.