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| Research article summary (published 30 Dec 2004): |
Loss of high-level perceptual knowledge of object structure in DAT.
Full Abstract
Visual object recognition and naming deficits in patients with dementia of the Alzheimer type (DAT) have typically been attributed to deficits in semantic processing. On a visual object naming test, a group of 10 mild, early stage DAT patients (mean MMSE=23.8) were found to suffer from anomia, compared to a group of 10 age-matched control participants. DAT naming errors were typically within category (commission), associative or circumlocutory errors. Performance on tests of low level visuo-spatial ability fell within the normal range. Together these results suggested that anomia resulted from a dysfunctional semantic system with intact visual perception. However, in a naming task using visually degraded images of familiar objects, the recognition threshold in DAT patients was significantly higher, indicating the need for a more visually complete object representation, before it could be accurately recognised. In a matched task using words visually degraded in an identical manner, the recognition threshold for DAT patients was very similar to that of the control group. It is argued that these results support the idea that impaired structural descriptions of objects (i.e., pre-semantic representation of an object within the visual perceptual system) combines with degraded semantic representations to produce anomia in mild early stage DAT.
Author information
Author/s: Done, D John (DJ); Hajilou, B Bruce (BB);
Affiliation: Department of Psychology, University of Hertfordshire, Hatfield Campus, College Lane, Hatfield AL10 9AB, UK.
Journal and publication information
Publication Type: Clinical Trial; Journal Article
Journal: Neuropsychologia (Neuropsychologia), published in England. (Language: eng)
Reference: 2005-; vol 43 (issue 1) : pp 60-8
Dates: Created 2004/10/18; Completed 2005/01/11; Revised 2009/11/11;
PMID: 15488906, status: MEDLINE (last retrieval date: 11/11/2009, IMS Date: )
Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.
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