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| Research article summary (published 30 May 2003): |
Categorization of object descriptions in Alzheimer's disease and frontotemporal dementia: limitation in rule-based processing.
Full Abstract
Studies of semantic memory in probable Alzheimer's disease (AD) have focused on the degradation of semantic knowledge, but other work in AD suggests an impairment in the semantic categorization processes that operate on this knowledge. We examined the categorization of object descriptions, where semantic category membership judgments were based on rule-based or similarity-based categorization processes. We found that AD patients were selectively limited in their semantic categorization under conditions requiring a rule-based approach. However, AD patients did not differ from healthy seniors under conditions based on judgments of overall similarity. We showed that this was not due to nonspecific or overall task-related difficulty associated with the rule condition by asking the subjects to use similarity-based judgments of perceptually degraded versions of the stimuli. The results of this condition did not differ from other similarity-based judgments but did differ from the rule-based condition in AD. Rule-based judgments of semantic category membership correlated with executive measures of inhibitory control and mental search, but not with measures of episodic memory or overall dementia severity, suggesting a contribution of executive resources to rule-based semantic categorization. Moreover, the pattern of limited rule-based categorization in AD closely resembled the performance profile of patients with frontotemporal dementia, further implying that executive resource limitations underlie AD patients' limited rule-based semantic categorization. These findings suggest that semantic memory difficulty in AD is due in part to a deficit in executive processes that are central to rule-based categorization in semantic memory.
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Author information
Author/s: Grossman, Murray (M); Smith, Edward E (EE); Koenig, Phyllis L (PL); Glosser, Guila (G); Rhee, Jina (J); Dennis, Kari (K);
Affiliation: Department of Neurology-2 Gibson, Hospital of the University of Pennsylvania, University of Pennsylvania, Philadelphia, Pennsylvania 19104-4283, USA. mgrossma(-atsign-)mail.med.upenn.edu
Grants: AG15116 (Agency:United States NIA) ; AG17586 (Agency:United States NIA) ; NS35867 (Agency:United States NINDS)
Journal and publication information
Publication Type: Comparative Study; Journal Article; Research Support, U.S. Gov't, P.H.S.
Journal: Cognitive, affective & behavioral neuroscience (Cogn Affect Behav Neurosci), published in United States. (Language: eng)
Reference: 2003-Jun; vol 3 (issue 2) : pp 120-32
Dates: Created 2003/08/28; Completed 2003/10/07; Revised 2007/11/14;
PMID: 12943327, status: MEDLINE (last retrieval date: 11/6/2008)
Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.
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