title: Common and unique gray matter correlates of episodic memory dysfunction in frontotemporal dementia and Alzheimer's disease.
abstract: Conflicting evidence exists regarding the integrity of episodic memory in the behavioral variant of frontotemporal dementia (bvFTD). Recent converging evidence suggests that episodic memory in progressive cases of bvFTD is compromised to the same extent as in Alzheimer's disease (AD). The underlying neural substrates of these episodic memory deficits, however, likely differ contingent on dementia type. In this study we sought to elucidate the neural substrates of episodic memory performance, across recall and recognition tasks, in both patient groups using voxel-based morphometry (VBM) analyses. We predicted that episodic memory dysfunction would be apparent in both patient groups but would relate to divergent patterns of neural atrophy specific to each dementia type. We assessed episodic memory, across verbal and visual domains, in 19 bvFTD, 18 AD patients, and 19 age- and education-matched controls. Behaviorally, patient groups were indistinguishable for immediate and delayed recall, across verbal and visual domains. Whole-brain VBM analyses revealed regions commonly implicated in episodic retrieval across groups, namely the right temporal pole, right frontal lobe, left paracingulate gyrus, and right anterior hippocampus. Divergent neural networks specific to each group were also identified. Whereas a widespread network including posterior regions such as the posterior cingulate cortex, parietal and occipital cortices was exclusively implicated in AD, the frontal and anterior temporal lobes underpinned the episodic memory deficits in bvFTD. Our results point to distinct neural changes underlying episodic memory decline specific to each dementia syndrome.
authors.affiliation: Neuroscience Research Australia, Barker Street, Randwick, Sydney, Australia; School of Medical Sciences, University of New South Wales, Sydney, Australia; ARC Centre of Excellence in Cognition and its Disorders, Sydney, Australia.
authors.forename: Muireann
authors.initials: M
authors.lastname: Irish
authors.forename: Olivier
authors.initials: O
authors.lastname: Piguet
authors.forename: John R
authors.initials: JR
authors.lastname: Hodges
authors.forename: Michael
authors.initials: M
authors.lastname: Hornberger
mesh_terms: D000368:Aged; D000544:Alzheimer Disease / Q000150:complications / Q000473:pathology* / Q000523:psychology; D001284:Atrophy / Q000473:pathology; D001921:Brain / Q000473:pathology*; D005260:Female; D057180:Frontotemporal Dementia / Q000150:complications / Q000473:pathology* / Q000523:psychology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008569:Memory Disorders / Q000209:etiology / Q000473:pathology*; D061212:Memory, Episodic; D011939:Mental Recall; D008875:Middle Aged; D036421:Nerve Fibers, Unmyelinated / Q000473:pathology*; D011569:Psychiatric Status Rating Scales; D021641:Recognition, Psychology; D013067:Speech Perception; D013997:Time Factors; D014796:Visual Perception
keywords: Alzheimer's disease; episodic memory; frontotemporal dementia; medial temporal lobes; posterior cingulate cortex; voxel-based morphometry