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Quantitative and Qualitative Impairments in Semantic Fluency, but not Phonetic Fluency, as a Potential Risk Factor for Alzheimer's Disease

Published online by Cambridge University Press:  21 February 2012

Brona O'Dowd*
Affiliation:
Centre for Magnetic Resonance, University of Queensland, Australia.
Jonathan Chalk
Affiliation:
Department of Medicine, University of Queensland, Australia.
Greig de Zubicaray
Affiliation:
Centre for Magnetic Resonance, University of Queensland, Australia.
*
Address for correspondence: Brona O'Dowd, BBSc (Hons) MClin (Neuro) PhD, Senior Research Officer (Neuropsychologist), Centre for Magnetic Resonance, University of Queensland, St Lucia, 4072. E-mail: [email protected]
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Abstract

Qualitative aspects of verbal fluency may be more useful in discerning the precise cause of any quantitative deficits in phonetic or category fluency, especially in the case of mild cognitive impairment (MCI), a possible intermediate stage between normal performance and Alzheimer's disease (AD). The aim of this study was to use both quantitative and qualitative (switches and clusters) methods to compare the phonetic and category verbal fluency performance of elderly adults with no cognitive impairment (n = 51), significant memory impairment (n = 16), and AD (n = 16). As expected, the AD group displayed impairments in all quantitative and qualitative measures of the two fluency tasks relative to their age- and education-matched peers. By contrast, the amnestic MCI group produced fewer animal names on the semantic fluency task than controls and showed normal performance on the phonetic fluency task. The MCI group's inferior category fluency performance was associated with a deficit in their category-switching rate rather than word cluster size. Overall, the results indicate that a semantic measure such as category fluency when used in conjunction with a test of episodic memory may increase the sensitivity for detecting preclinical AD. Future research using external cues and other measures of set shifting capacity may assist in clarifying the origin of the amnestic MCI-specific category-switching deficiency.

Type
Articles
Copyright
Copyright © Cambridge University Press 2004

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