title: Contrasting prefrontal cortex contributions to episodic memory dysfunction in behavioural variant frontotemporal dementia and Alzheimer's disease.
abstract: Recent evidence has questioned the integrity of episodic memory in behavioural variant frontotemporal dementia (bvFTD), where recall performance is impaired to the same extent as in Alzheimer's disease (AD). While these deficits appear to be mediated by divergent patterns of brain atrophy, there is evidence to suggest that certain prefrontal regions are implicated across both patient groups. In this study we sought to further elucidate the dorsolateral (DLPFC) and ventromedial (VMPFC) prefrontal contributions to episodic memory impairment in bvFTD and AD. Performance on episodic memory tasks and neuropsychological measures typically tapping into either DLPFC or VMPFC functions was assessed in 22 bvFTD, 32 AD patients and 35 age- and education-matched controls. Behaviourally, patient groups did not differ on measures of episodic memory recall or DLPFC-mediated executive functions. BvFTD patients were significantly more impaired on measures of VMPFC-mediated executive functions. Composite measures of the recall, DLPFC and VMPFC task scores were covaried against the T1 MRI scans of all participants to identify regions of atrophy correlating with performance on these tasks. Imaging analysis showed that impaired recall performance is associated with divergent patterns of PFC atrophy in bvFTD and AD. Whereas in bvFTD, PFC atrophy covariates for recall encompassed both DLPFC and VMPFC regions, only the DLPFC was implicated in AD. Our results suggest that episodic memory deficits in bvFTD and AD are underpinned by divergent prefrontal mechanisms. Moreover, we argue that these differences are not adequately captured by existing neuropsychological measures.
authors: Neuroscience Research Australia, Randwick, Sydney, New South Wales, Australia ; Department of Psychology, Macquarie University, Sydney, New South Wales, Australia ; Australian Research Council Centre of Excellence in Cognition and its Disorders, Sydney, New South Wales, Australia.
authors: Stephanie
authors: S
authors: Wong
authors: Neuroscience Research Australia, Randwick, Sydney, New South Wales, Australia.
authors: Emma
authors: E
authors: Flanagan
authors: Department of Psychology, Macquarie University, Sydney, New South Wales, Australia ; Australian Research Council Centre of Excellence in Cognition and its Disorders, Sydney, New South Wales, Australia.
authors: Greg
authors: G
authors: Savage
authors: Neuroscience Research Australia, Randwick, Sydney, New South Wales, Australia ; Australian Research Council Centre of Excellence in Cognition and its Disorders, Sydney, New South Wales, Australia ; School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia.
authors: John R
authors: JR
authors: Hodges
authors: Neuroscience Research Australia, Randwick, Sydney, New South Wales, Australia ; Australian Research Council Centre of Excellence in Cognition and its Disorders, Sydney, New South Wales, Australia ; School of Medical Sciences, University of New South Wales, Sydney, New South Wales, Australia.
authors: Michael
authors: M
authors: Hornberger
mesh_terms: D000368:Aged; D000544:Alzheimer Disease / Q000175:diagnosis / Q000503:physiopathology*; D001284:Atrophy; D001519:Behavior; D003071:Cognition; D005260:Female; D057180:Frontotemporal Dementia / Q000175:diagnosis / Q000503:physiopathology*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D061212:Memory, Episodic; D011939:Mental Recall; D008875:Middle Aged; D009483:Neuropsychological Tests; D017397:Prefrontal Cortex / Q000473:pathology / Q000503:physiopathology*; D012307:Risk Factors