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Deficient Symbol Processing in Alzheimer Disease

Toepper, Max PhD*,†,‡; Steuwe, Carolin MSc*; Beblo, Thomas PhD*; Bauer, Eva PhD; Boedeker, Sebastian BSc§; Thomas, Christine MD*,‡; Markowitsch, Hans J. PhD§,∥; Driessen, Martin MD*; Sammer, Gebhard PhD

Alzheimer Disease & Associated Disorders: October-December 2014 - Volume 28 - Issue 4 - p 340–346
doi: 10.1097/WAD.0000000000000035
Original Articles
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Symbols and signs have been suggested to improve the orientation of patients suffering from Alzheimer disease (AD). However, there are hardly any studies that confirm whether AD patients benefit from signs or symbols and which symbol characteristics might improve or impede their symbol comprehension. To address these issues, 30 AD patients and 30 matched healthy controls performed a symbol processing task (SPT) with 4 different item categories. A repeated-measures analysis of variance was run to identify impact of different item categories on performance accuracy in both the experimental groups. Moreover, SPT scores were correlated with neuropsychological test scores in a broad range of other cognitive domains. Finally, diagnostic accuracy of the SPT was calculated by a receiver-operating characteristic curve analysis. Results revealed a global symbol processing dysfunction in AD that was associated with semantic memory and executive deficits. Moreover, AD patients showed a disproportional performance decline at SPT items with visual distraction. Finally, the SPT total score showed high sensitivity and specificity in differentiating between AD patients and healthy controls. The present findings suggest that specific symbol features impede symbol processing in AD and argue for a diagnostic benefit of the SPT in neuropsychological assessment.

Departments of *Psychiatry and Psychotherapy Bethel, Research Department

Geriatric Psychiatry, Evangelic Hospital Bielefeld (EvKB), Bethesdaweg

§Department of Psychology, University of Bielefeld

Cognitive Interaction Technology, Center of Excellence (CITEC), University of Bielefeld, Universitätsstraße 25, Bielefeld

Justus-Liebig-University of Giessen, Cognitive Neuroscience at Centre for Psychiatry, Giessen, Germany

The authors declare no conflicts of interest.

Reprints: Max Toepper, PhD, Department of Psychiatry and Psychotherapy Bethel, Research Department, Evangelic Hospital Bielefeld (EvKB), Remterweg 69-71, Bielefeld D-33617, Germany (e-mail: max.toepper@evkb.de).

Received October 15, 2013

Accepted February 7, 2014

© 2014 by Lippincott Williams & Wilkins.