Functional connectivity in obsessive-compulsive disorder : a magnetoencephalographic study

Abstract

Researchers have associated obsessive-compulsive disorder (OCD) with aberrant functional connectivity among a number of brain regions. Analysis of functional connectivity in the resting state may provide important evidence in elucidating the pathophysiology of OCD. The aim of the present study is to evaluate whether patients with OCD exhibit differences in resting-state functional connectivity when compared to healthy controls using MEG. We recruited 24 patients with OCD (21 males, 3 females), in addition to 22 healthy controls (19 males, 3 females). Prior to our analysis of functional connectivity, we examined group differences in brain activity and oscillatory activity and the association between overall OCD symptom severity and regional oscillatory activity. We utilized the phase locking value (PLV) to examine group differences in functional connectivity between regions of interest and to determine the distribution of functional hubs based on weighted-graph theory. Patients with OCD exhibited significantly reduced phase synchronization in all band frequencies, with the exception of the delta band, when compared with healthy controls. In addition, the OCD group exhibited significantly lower phase synchronization in theta and gamma band frequencies between the left insula and right limbic regions, as well as among left orbitofrontal areas. A similar tendency was observed with respect to alpha and beta band frequencies, though patients with OCD exhibited greater connectivity with lower phase synchrony than healthy controls. We further observed differences in the distribution of the upper functional hubs for each group in all band frequencies. Healthy controls exhibited a greater number of central hubs in the orbitofrontal and left insular regions, whereas patients in the OCD group exhibited additional functional hubs in the temporo-parietal and cingulate regions. The results of the present study indicate that, during the resting state, patients with OCD exhibit lower phase synchronization and fewer functional hubs in ventral areas, including the orbitofrontal, limbic, and insular regions when compared with healthy controls. These findings suggest that reduced functional connectivity in areas of the limbic loop and functionally connected neighboring regions reflect an underlying pathophysiology associated with dysfunction of inhibitory control in patients with OCD.