Altered structural-functional connectivity bandwidth in major depressive disorder: A multiplex network analysis

Major depressive disorder (MDD) is a prevalent and severe mental illness that may lead to abnormalities in both brain structure and functional connectivity. Although existing research has extensively reported changes in brain network connectivity in MDD patients, the interaction mechanisms between structural connectivity and functional connectivity remain unclear. This study aims to investigate the role of structural connectivity (SC) in influencing functional connectivity (FC) in patients with MDD, employing multilayer network statistical approaches. We introduce a novel measure, the SC-FC bandwidth, to assess the communication capacity between regions with synchronized functions. We investigated the connection between brain SC and FC in 57 individuals with MDD and 59 healthy control participants. Using diffusion tensor imaging (DTI) and resting-state functional magnetic resonance imaging (rs-fMRI) data, we constructed SC and FC networks and examined SC-FC polygons and bandwidths. The study found that functional connectivity in MDD patients is primarily mediated through indirect structural pathways, with limited contribution from higher-order pathways. Significant differences between MDD patients and healthy controls were observed across multiple functional sub-networks. Moreover, a strong positive correlation between SC-FC bandwidth and functional connectivity was identified. SC-FC bandwidth in specific sub-networks was significantly correlated with clinical ratings in MDD patients. By applying multilayer network analysis, this study highlights changes in SC-FC polygons and bandwidth in MDD patients, underscoring the essential role of structural connectivity in facilitating functional interactions. These results offer a fresh perspective on the neural mechanisms underlying MDD.