Altered Intramodular Functional Connectivity in Drug Naïve Obsessive-Compulsive Disorder Patients

Modular functional alterations were shown in obsessive-compulsive disorder (OCD) patients from previous functional magnetic resonance imaging (fMRI) studies. However, most studies considered each module as a specific node and ignore the intramodular connectivity information. In this paper, we investigated the intramodular functional connectivity (FC) alterations in drug naive OCD patients using a whole brain graph theoretical approach for functional modular parcellation. Seventy-three drug-naive OCD patients and seventy-eight matched healthy controls were included in this study. We utilized infomap algorithm for modules detection. The functional connectivity strength (FCS) was calculated within each module to obtain the FC between a given voxel and all other voxels in the module. We found increased FCS in precentral and postcentral gyrus within sensor-motor network (SMN) and decreased FCS in insula within salience network (SN). Moreover, FC within SMN was negatively correlated with YBOCS- compulsions scores, while FC within SN was negatively correlated with YBOCS-total, compulsions and obsessions scores. Our findings brought useful insights in understanding the pathophysiology of OCD.