title: Structural connectivity of the default mode network and cognition in Alzheimer׳s disease.
abstract: Disconnectivity between the Default Mode Network (DMN) nodes can cause clinical symptoms and cognitive deficits in Alzheimer׳s disease (AD). We aimed to examine the structural connectivity between DMN nodes, to verify the extent in which white matter disconnection affects cognitive performance. MRI data of 76 subjects (25 mild AD, 21 amnestic Mild Cognitive Impairment subjects and 30 controls) were acquired on a 3.0T scanner. ExploreDTI software (fractional Anisotropy threshold=0.25 and the angular threshold=60°) calculated axial, radial, and mean diffusivities, fractional anisotropy and streamline count. AD patients showed lower fractional anisotropy (P=0.01) and streamline count (P=0.029), and higher radial diffusivity (P=0.014) than controls in the cingulum. After correction for white matter atrophy, only fractional anisotropy and radial diffusivity remained significantly lower in AD compared to controls (P=0.003 and P=0.05). In the parahippocampal bundle, AD patients had lower mean and radial diffusivities (P=0.048 and P=0.013) compared to controls, from which only radial diffusivity survived for white matter adjustment (P=0.05). Regression models revealed that cognitive performance is also accounted for by white matter microstructural values. Structural connectivity within the DMN is important to the execution of high-complexity tasks, probably due to its relevant role in the integration of the network.
authors.affiliation: Neuroimaging Laboratory, Department of Neurology, University of Campinas (Unicamp), Brazil.
authors.forename: Marina
authors.initials: M
authors.lastname: Weiler
authors.affiliation: Neuroimaging Laboratory, Department of Neurology, University of Campinas (Unicamp), Brazil.
authors.forename: Brunno Machado
authors.initials: BM
authors.lastname: de Campos
authors.affiliation: Neuroimaging Laboratory, Department of Neurology, University of Campinas (Unicamp), Brazil.
authors.forename: Mateus Henrique
authors.initials: MH
authors.lastname: Nogueira
authors.affiliation: Unit for Neuropsychology and Neurolinguistics, Department of Neurology, University of Campinas (Unicamp), Brazil.
authors.forename: Benito
authors.initials: B
authors.lastname: Pereira Damasceno
authors.affiliation: Neuroimaging Laboratory, Department of Neurology, University of Campinas (Unicamp), Brazil.
authors.forename: Fernando
authors.initials: F
authors.lastname: Cendes
authors.affiliation: Neuroimaging Laboratory, Department of Neurology, University of Campinas (Unicamp), Brazil; Unit for Neuropsychology and Neurolinguistics, Department of Neurology, University of Campinas (Unicamp), Brazil. Electronic address: mbalth@unicamp.br.
authors.forename: Marcio L F
authors.initials: ML
authors.lastname: Balthazar
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000150:complications / Q000473:pathology*; D016880:Anisotropy; D001284:Atrophy / Q000150:complications / Q000473:pathology; D001921:Brain / Q000473:pathology*; D001931:Brain Mapping; D016022:Case-Control Studies; D003071:Cognition; D060825:Cognitive Dysfunction / Q000473:pathology*; D038524:Diffusion Magnetic Resonance Imaging; D056324:Diffusion Tensor Imaging / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D008297:Male; D009413:Nerve Fibers, Myelinated / Q000473:pathology*; D009483:Neuropsychological Tests; D012044:Regression Analysis
keywords: Amnestic mild cognitive impairment; Cognitive performance; Diffusion tensor imaging