title: Altered effective connectivity of the default mode network in resting-state amnestic type mild cognitive impairment.
abstract: Amnestic mild cognitive impairment (aMCI) is the transitional, heterogeneous continuum from normal elderly to Alzheimer's disease (AD). Previous studies have shown that brain functional activity in the default mode network (DMN) is impaired in aMCI patients with saliently cognitive and memory decline. However, the effective connectivity among the spatially isolated, but functionally related areas within the DMN in aMCI patients remains largely unknown. The present study examined dysfunctional connectivity of the DMN by combining an independent component analysis (ICA) approach with multivariate Granger causality analysis (mGCA) in 18 aMCI patients and 18 age-matched cognitively normal elderly. Results from mGCA showed decreased effective connectivity occurred among the middle temporal gyrus (MTG), hippocampus (HC) and fusiform gyrus (FG), as well as between the precuneus/posterior cingulate cortex (PreCN/PCC) and HC in patients with aMCI. Such an impaired connectivity was also correlated with patients' cognitive performance of the auditory verbal learning. Moreover, enhanced effective connectivity within frontal cortex emerged, which may maintain memory functions after attenuated connections within DMN activity. These findings may elucidate the dysfunctional processes in brain networks of aMCI patients, highlighting the importance of connectivity changes in the pathophysiology of aMCI.
authors: School of Psychology, Shaanxi Normal University, Xi'an, China.
authors: Hao
authors: H
authors: Yan
authors: Yumei
authors: Y
authors: Zhang
authors: Hongyan
authors: H
authors: Chen
authors: Yonghui
authors: Y
authors: Wang
authors: Yijun
authors: Y
authors: Liu
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000647:Amnesia / Q000150:complications*; D001921:Brain / Q000473:pathology*; D001931:Brain Mapping; D016022:Case-Control Studies; D060825:Cognitive Dysfunction / Q000150:complications*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D008959:Models, Neurological; D009483:Neuropsychological Tests; D012146:Rest