Brain network modularity study in treatment-naïve, first episode major depressive disorder

Abstract

Objective To examine the changes of functional network modularity in treatment-naive, first episode major depressive disorder(MDD)patients and the relationship between modularity related indicators and clinical severity. Methods 50 treatment-naive, first episode patients with MDD and 37 age, gender, and education level matched healthy control(HC)were included. They all received fMRI scanning during quiet, eye closed and awake state. We used the 90 automated anatomical labeling(ALL)template to construct functional connectivity matrix. Several modularity related indicators, including global modularization, intra-module connectivity, inter-module connectivity, were computed. The differences in these indicators were compared between MDD group and HC group. The Pearson correlation analysis were performed to show correlation between the regions showing modularity changes and severity of disease. Result There were 4 modules in MDD patients and 3 modules in HC group. MDD patients showed significant decline in modularity degree in the left middle orbitofrontal gyrus, the inferior orbitofrontal gyrus, the superior occipital gyrus, and the rolandic operculum. No significant correlation were found between modularity degree values of these four regions and the severity of disease(r=0.21,P>0.05). No significant differences were found in global modularization, intra connectivity and inter connectivity between two groups(r=0.11,P>0.05). Conclusion MDD patients may have changed connectivity in orbitofrontal cortex, superior occipital gyrus and rolandic operculum, which are relevant nodes of neural network basis of MDD. Key words: Depressive disorder; Magnetic resonance imaging; Functional brain network; Modularity