Neurocognitive contributions to verbal fluency deficits in frontotemporal lobar degeneration.
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.
Libon
D J
DJ
Department of Neurology, Drexel University, Philadelphia, PA 19102, USA. dlibon@drexelmed.edu
McMillan
C
C
Gunawardena
D
D
Powers
C
C
Massimo
L
L
Khan
A
A
Morgan
B
B
Farag
C
C
Richmond
L
L
Weinstein
J
J
Moore
P
P
Coslett
H B
HB
Chatterjee
A
A
Aguirre
G
G
Grossman
M
M
D000368:Aged; D001039:Aphasia, Broca / Q000175:diagnosis* / Q000209:etiology* / Q000503:physiopathology; D003072:Cognition Disorders / Q000175:diagnosis* / Q000209:etiology* / Q000503:physiopathology; D003704:Dementia / Q000150:complications* / Q000473:pathology / Q000523:psychology; D004185:Disability Evaluation; D018450:Disease Progression; D005260:Female; D005625:Frontal Lobe / Q000473:pathology / Q000503:physiopathology; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D007807:Language Tests; D008279:Magnetic Resonance Imaging; D008297:Male; D008569:Memory Disorders / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology; D008875:Middle Aged; D009415:Nerve Net / Q000473:pathology / Q000503:physiopathology; D009434:Neural Pathways / Q000473:pathology / Q000503:physiopathology; D009483:Neuropsychological Tests; D012720:Severity of Illness Index; D013702:Temporal Lobe / Q000473:pathology / Q000503:physiopathology
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