PURPOSE: To investigate the topologic reorganization of the default-mode network (DMN) in patients with mild cognitive impairment (MCI) and whether, relative to healthy control subjects, patients with MCI would be more likely to show disrupted functional connectivity and altered topological configuration of the DMN during the memory task compared with that observed during the resting state. MATERIALS AND METHODS: This study was approved by the institutional review board of Beijing Normal University Imaging Center for Brain Research. Written informed consent was obtained from each participant. Healthy control subjects (n = 26) and patients with amnestic MCI (aMCI) (n = 25) performed an episodic memory task and also rested while undergoing functional magnetic resonance imaging. Task-induced deactivations were identified and parcellated into different regions associated with the DMN. Functional connectivity across all pairs of regions was computed to construct the DMN architecture. Graph theoretical approaches were used to characterize topological properties of this network. RESULTS: Patients with aMCI showed similar deactivation in the DMN to that observed in healthy control subjects (P > .05) but showed significantly decreased anterior-to-posterior functional connectivity only during the task (P < .05). Significant increases in local efficiency (P < .05), but not in global efficiency (P > .05), were observed in aMCI only during the task. Decreased functional connectivity was predictive of increased local efficiency (r = -0.35, P = .015). Significant correlations between these network measures and cognitive performance (P < .05) indicated their potential use as early markers to assess the risk of Alzheimer disease (AD). CONCLUSION: This study suggests the early onset functional reorganization of the DMN toward a nonoptimized regularity configuration in aMCI and expands the understanding of dynamic functional reorganization in brain networks along the continuum from normal aging to AD dementia.
PURPOSE: To investigate the topologic reorganization of the default-mode network (DMN) in patients with mild cognitive impairment (MCI) and whether, relative to healthy control subjects, patients with MCI would be more likely to show disrupted functional connectivity and altered topological configuration of the DMN during the memory task compared with that observed during the resting state. MATERIALS AND METHODS: This study was approved by the institutional review board of Beijing Normal University Imaging Center for Brain Research. Written informed consent was obtained from each participant. Healthy control subjects (n = 26) and patients with amnestic MCI (aMCI) (n = 25) performed an episodic memory task and also rested while undergoing functional magnetic resonance imaging. Task-induced deactivations were identified and parcellated into different regions associated with the DMN. Functional connectivity across all pairs of regions was computed to construct the DMN architecture. Graph theoretical approaches were used to characterize topological properties of this network. RESULTS:Patients with aMCI showed similar deactivation in the DMN to that observed in healthy control subjects (P > .05) but showed significantly decreased anterior-to-posterior functional connectivity only during the task (P < .05). Significant increases in local efficiency (P < .05), but not in global efficiency (P > .05), were observed in aMCI only during the task. Decreased functional connectivity was predictive of increased local efficiency (r = -0.35, P = .015). Significant correlations between these network measures and cognitive performance (P < .05) indicated their potential use as early markers to assess the risk of Alzheimer disease (AD). CONCLUSION: This study suggests the early onset functional reorganization of the DMN toward a nonoptimized regularity configuration in aMCI and expands the understanding of dynamic functional reorganization in brain networks along the continuum from normal aging to AD dementia.
Authors: Wutao Lou; Lin Shi; Defeng Wang; Cindy W C Tam; Winnie C W Chu; Vincent C T Mok; Sheung-Tak Cheng; Linda C W Lam Journal: Hum Brain Mapp Date: 2015-05-28 Impact factor: 5.038
Authors: S Duke Han; Patricia A Boyle; Lei Yu; Debra A Fleischman; Konstantinos Arfanakis; Sue Leurgans; David A Bennett Journal: Arch Gerontol Geriatr Date: 2014-05-16 Impact factor: 3.250
Authors: Rongfeng Qi; Jun Ke; U Joseph Schoepf; Akos Varga-Szemes; Cole M Milliken; Chang Liu; Qiang Xu; Fangyu Wang; Long Jiang Zhang; Guang Ming Lu Journal: Mol Neurobiol Date: 2015-12-03 Impact factor: 5.590
Authors: Ludovica Griffanti; Ottavia Dipasquale; Maria M Laganà; Raffaello Nemni; Mario Clerici; Stephen M Smith; Giuseppe Baselli; Francesca Baglio Journal: Front Hum Neurosci Date: 2015-08-11 Impact factor: 3.169