HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Figures Only Full Text Full Text (PDF) Correspondence: Submit a response Alert me when this article is cited Alert me when Correspondence are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Libon, D. J. Articles by Grossman, M. PubMed PubMed Citation Articles by Libon, D. J. Articles by Grossman, M. Related Collections All Cognitive Disorders/Dementia Alzheimer's disease Frontotemporal dementia Cognitive neuropsychology in dementia Assessment of cognitive disorders/dementia

Neurocognitive contributions to verbal fluency deficits in frontotemporal lobar degeneration

From the Department of Neurology (D.J.L.), Drexel University, Philadelphia, PA; and Department of Neurology (C.M., D.G., C.P., L.M., A.K., B.M., C.F., L.R., J.W., P.M., H.B.C., A.C., G.A., M.G.), University of Pennsylvania School of Medicine, Philadelphia, PA.

Address correspondence and reprint requests to Dr. David J. Libon, Drexel University College of Medicine, New College Building, Mail Stop 423, 245 North 15th St., Philadelphia, PA 19102 dlibon{at}drexelmed.edu

Objective: To test the hypothesis that different neurocognitive networks underlie verbal fluency deficits in frontotemporal lobar degeneration (FTLD).

Methods: Letter ("FAS") and semantic ("animal") fluency tests were administered to patients with a behavioral/dysexecutive disorder (bvFTLD; n = 71), semantic dementia (SemD; n = 21), and progressive nonfluent aphasia (PNFA; n = 26). Tests measuring working memory, naming/lexical retrieval, and semantic knowledge were also obtained. MRI voxel-based morphometry (VBM) studies were obtained on a subset of these patients (bvFTLD, n = 51; PNFA, n = 11; SemD, n = 10).

Results: Patients with SemD were disproportionately impaired on the semantic fluency measure. Reduced output on this test was correlated with impaired performance on naming/lexical retrieval tests. VBM analyses related reduced letter and semantic fluency to anterior and inferior left temporal lobe atrophy. Patients with bvFTLD were equally impaired on both fluency tests. Poor performance on both fluency tests was correlated with low scores on working memory and naming/lexical retrieval measures. In this group, MRI-VBM analyses related letter fluency to bilateral frontal atrophy and semantic fluency to left frontal/temporal atrophy. Patients with PNFA were also equally impaired on fluency tests. Reduced semantic fluency output was correlated with reduced performance on naming/lexical retrieval tests. MRI-VBM analyses related semantic fluency to the right frontal lobe and letter fluency to left temporal atrophy.

Conclusions: Distinct neurocognitive networks underlie impaired performance on letter and semantic fluency tests in frontotemporal lobar degeneration subgroups.

Abbreviations: AD = Alzheimer disease; ANOVA = analysis of variance; bvFTLD = behavioral/dysexecutive subgroup; FTLD = frontotemporal lobar degeneration; MMSE = Mini-Mental State Examination; MNI = Montreal Neurological Institute; MR = magnetic resonance; PNFA = progressive nonfluent aphasia; SemD = semantic dementia; TE = echo time; TR = repetition time; VBM = voxel-based morphometry.

Disclosure: Author disclosures are provided at the end of the article.

Received December 23, 2008. Accepted in final form May 15, 2009.