Altered interhemispheric functional connectivity in remitted bipolar disorder: A Resting State fMRI Study

Lianping Zhao,Zhangzhang Qi,Li Huang,Ying Wang,Yao Sun,Shuming Zhong,Zhongping Zhang,Yanbin Jia

doi:10.1038/s41598-017-04937-6

Abstract

Abnormalities in structural and functional brain connectivity have been increasingly reported in patients with bipolar disorder (BD). However, alterations of remitted BD (RBD) in functional connectivity between the cerebral hemispheres are still not well understood. This study was designed to analyze the pattern of the interhemispheric functional connectivity of the whole brain in patients with remitted BD during resting state. Twenty patients with RBD and 38 healthy controls (HC) underwent the resting-state functional magnetic resonance imaging. The functional connectivity between any pair of symmetrical interhemispheric voxels (i.e., functional homotopy) was measured by voxel-mirrored homotopic connectivity (VMHC). The patients with RBD showed lower VMHC than HC in the middle frontal gyrus and precentral gyrus. No regions of increased VMHC were detected in the RBD patients. There were no significant correlations between the VMHC values in these regions and the clinical variables. These findings suggest substantial impairment of interhemispheric coordination in RBD and they may represent trait, rather than state, neurobiological feature of brain function in BD.

Highlights

Bipolar disorder (BD) is a chronic, severe, and fluctuating mental disorder and the worldwide prevalence of the bipolar disorder (BD) spectrum is 1–4%1
Four patients with remitted BD (RBD) and four healthy controls (HC) were excluded from further analyses due to excessive head motion during the image acquisition
There were no significant differences in sex, age and years of education between the RBD group and the HC group

Summary

Introduction

Bipolar disorder (BD) is a chronic, severe, and fluctuating mental disorder and the worldwide prevalence of the BD spectrum is 1–4%1. Resting-state fMRI (rs-fMRI), which reveals the patterns of coherent spontaneous fluctuations of blood oxygen level dependent (BOLD) signals[12], provides fresh insights intra-and interhemispheric functional connectivity. There are no studies to investigate possible impairment of homotopic resting-state functional connectivity in RBD patients so far. We compared the interhemispheric resting-state functional connectivity in patients with RBD and healthy controls (HC) by use of VMHC analysis. Reduced VMHC values in patients with RBD were anticipated, which would suggest an impairment of interhemispheric functional coordination. We believe such data will contribute to our improved understanding of the pathophysiology of BD

Methods

Discussion

Conclusion