title: Altered causal connectivity of resting state brain networks in amnesic MCI.
abstract: Most neuroimaging studies of resting state networks in amnesic mild cognitive impairment (aMCI) have concentrated on functional connectivity (FC) based on instantaneous correlation in a single network. The purpose of the current study was to investigate effective connectivity in aMCI patients based on Granger causality of four important networks at resting state derived from functional magnetic resonance imaging data--default mode network (DMN), hippocampal cortical memory network (HCMN), dorsal attention network (DAN) and fronto-parietal control network (FPCN). Structural and functional MRI data were collected from 16 aMCI patients and 16 age, gender-matched healthy controls. Correlation-purged Granger causality analysis was used, taking gray matter atrophy as covariates, to compare the group difference between aMCI patients and healthy controls. We found that the causal connectivity between networks in aMCI patients was significantly altered with both increases and decreases in the aMCI group as compared to healthy controls. Some alterations were significantly correlated with the disease severity as measured by mini-mental state examination (MMSE), and California verbal learning test (CVLT) scores. When the whole-brain signal averaged over the entire brain was used as a nuisance co-variate, the within-group maps were significantly altered while the between-group difference maps did not. These results suggest that the alterations in causal influences may be one of the possible underlying substrates of cognitive impairments in aMCI. The present study extends and complements previous FC studies and demonstrates the coexistence of causal disconnection and compensation in aMCI patients, and thus might provide insights into biological mechanism of the disease.
authors.affiliation: Department of Radiology, Xuanwu Hospital, Capital Medical University, Beijing, China; Beijing Key Laboratory of Magnetic Resonance Imaging and Brain Informatics, Beijing, China; Key Laboratory for Neurodegenerative Diseases, Ministry of Education, Beijing, PR China.
authors.forename: Peipeng
authors.initials: P
authors.lastname: Liang
authors.affiliation: Wallace H Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia, United States of America.
authors.forename: Zhihao
authors.initials: Z
authors.lastname: Li
authors.affiliation: Auburn University MRI Research Center, Department of Electrical and Computer Engineering, and Department of Psychology, Auburn University, Auburn, Alabama, United States of America.
authors.forename: Gopikrishna
authors.initials: G
authors.lastname: Deshpande
authors.affiliation: Department of Radiology, Xuanwu Hospital, Capital Medical University, Beijing, China; Beijing Key Laboratory of Magnetic Resonance Imaging and Brain Informatics, Beijing, China; Key Laboratory for Neurodegenerative Diseases, Ministry of Education, Beijing, PR China.
authors.forename: Zhiqun
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Wallace H Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia, United States of America.
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Hu
authors.affiliation: Department of Radiology, Xuanwu Hospital, Capital Medical University, Beijing, China; Beijing Key Laboratory of Magnetic Resonance Imaging and Brain Informatics, Beijing, China; Key Laboratory for Neurodegenerative Diseases, Ministry of Education, Beijing, PR China.
authors.forename: Kuncheng
authors.initials: K
authors.lastname: Li
mesh_terms: D000368:Aged; D000647:Amnesia / Q000503:physiopathology*; D001288:Attention / Q000502:physiology; D001921:Brain / Q000503:physiopathology*; D002540:Cerebral Cortex / Q000503:physiopathology; D060825:Cognitive Dysfunction / Q000503:physiopathology*; D003710:Demography; D005260:Female; D006257:Head; D006801:Humans; D008297:Male; D008568:Memory / Q000502:physiology; D009038:Motion; D009415:Nerve Net / Q000503:physiopathology*; D009483:Neuropsychological Tests; D012146:Rest