A feasibility study on inferring connectivity changes in frontal lobes of MDD patients via spectral DCM

Many studies have shown that major depressive disorder (MDD) is highly relevant to the dysfunction of frontal lobes. Given the crucial role of brain network organization for MDD, this work focuses on inferring effective connectivity patterns and their changes in the frontal lobes of non-depressive and MDD subjects. We collected frontopolar left (Fp1), frontopolar right (Fp2), and frontal midline (Fz) channels of resting electroencephalogram (EEG) from 22 subjects with non-depressive states (non-depressive group), 23 subjects with mild depression (mild MDD group) and 12 subjects with moderate depression (moderate MDD group). Complete Physiology-Based Model was introduced to simulate the EEG signals of brain activities in the three targeted lobes. Then, spectral dynamic causal modelling was performed to investigate effective connectivity and its changes between the three targeted channels. The findings suggest that MDD groups exhibit a significant decline in the average strength of excitatory connectivity between pyramidal cells of the three lobes, compared to the non-depressed group. Additionally, the fluctuation of connectivity across trials among frontal lobes decreases in the mild and moderate MDD groups. The MDD groups also showed frontal asymmetry, specifically in the form of significant differences in bidirectional excitatory connections between Fp1 and Fp2. These effective connectivity changes of frontal lobes may indicate its clinical potential in future research on depression.