title: Resting-state brain organization revealed by functional covariance networks.
abstract: BACKGROUND
  Brain network studies using techniques of intrinsic connectivity network based on fMRI time series (TS-ICN) and structural covariance network (SCN) have mapped out functional and structural organization of human brain at respective time scales. However, there lacks a meso-time-scale network to bridge the ICN and SCN and get insights of brain functional organization.
  
  
  RESULTS
  We proposed a functional covariance network (FCN) method by measuring the covariance of amplitude of low-frequency fluctuations (ALFF) in BOLD signals across subjects, and compared the patterns of ALFF-FCNs with the TS-ICNs and SCNs by mapping the brain networks of default network, task-positive network and sensory networks. We demonstrated large overlap among FCNs, ICNs and SCNs and modular nature in FCNs and ICNs by using conjunctional analysis. Most interestingly, FCN analysis showed a network dichotomy consisting of anti-correlated high-level cognitive system and low-level perceptive system, which is a novel finding different from the ICN dichotomy consisting of the default-mode network and the task-positive network.
  
  
  CONCLUSIONS
  The current study proposed an ALFF-FCN approach to measure the interregional correlation of brain activity responding to short periods of state, and revealed novel organization patterns of resting-state brain activity from an intermediate time scale.
authors.affiliation: Department of Medical Imaging, Jinling Hospital, Nanjing University School of Medicine, Nanjing, Jiangsu Province, China.
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: Zhang
authors.forename: Wei
authors.initials: W
authors.lastname: Liao
authors.forename: Xi-Nian
authors.initials: XN
authors.lastname: Zuo
authors.forename: Zhengge
authors.initials: Z
authors.lastname: Wang
authors.forename: Cuiping
authors.initials: C
authors.lastname: Yuan
authors.forename: Qing
authors.initials: Q
authors.lastname: Jiao
authors.forename: Huafu
authors.initials: H
authors.lastname: Chen
authors.forename: Bharat B
authors.initials: BB
authors.lastname: Biswal
authors.forename: Guangming
authors.initials: G
authors.lastname: Lu
authors.forename: Yijun
authors.initials: Y
authors.lastname: Liu
mesh_terms: D001921:Brain / Q000502:physiology*; D001931:Brain Mapping; D016000:Cluster Analysis; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009434:Neural Pathways / Q000502:physiology*; D012146:Rest / Q000502:physiology*; D055815:Young Adult