Network analysis for investigating functional connectivity in major depression disorder: A functional magnetic images (fMRI) study

Major depressive disorder (MDD) is a common mental disorder characterized by a pervasive low mood. The aim of this study is to investigate the difference of network properties of functional network derived from functional magnetic resonance imaging (fMRI) between the healthy subjects and the patients with major depression disorder. The functional MR images were acquired from 13 healthy subjects and 19 patients with major depression disorder. All images of each subject were parcellated into cortical and sub-cortical regions which were defined as the nodes of the network. The functional relations between these regions were estimated by the timefrequency cross mutual information (TFCMI) followed by a thresholding to construct a set of undirected graphs. Our findings indicated that the MDD patients presented lower degree, strength and cliquishness of connections, whereas longer mean path length in the brain network. This suggested the reduced efficiency of the brain network for MDD patients. In addition, the network properties of MDD patients were altered significantly in some regions in the frontal lobes and limbic system which were in good agreement with the dysfunction connectivity reported by the previous literatures in the study of major depression disorder.