Abstract
<title>Abstract</title> <p>Repetitive transcranial magnetic stimulation (rTMS) of the left dorsolateral prefrontal cortex (dlPFC) is an established treatment for treatment-resistant depression (TRD), but its molecular and network-level mechanisms remain incompletely understood, and the two levels have rarely been measured together. We studied eleven patients with TRD (6 female; mean age 47.5 ± 12.5 years) who underwent 20 sessions of 10 Hz left-dlPFC rTMS over 6 weeks, combining two complementary analytic arms in the same patients: a hypothesis-driven arm testing pre-specified changes in source-reconstructed resting-state EEG directed connectivity (Phase Slope Index, PSI) across the default mode (DMN), frontoparietal (FPN), salience (SN) and dorsal attention (DAN) networks, and a discovery arm profiling plasma microRNA (miRNA) expression by next-generation sequencing. Clinically, treatment produced significant improvement on the IDS-30 (p = 0.008), BDI-II (p = 0.005), and the negative-affect and anhedonia subscales of the LAPS. In the connectivity arm, the pre-specified limbic DMN changes were confirmed—directed drive from the posterior cingulate cortex to the subgenual anterior cingulate decreased, and directed drive from the dlPFC to the posterior cingulate increased—and the largest single effect in the dataset was a decrease in directed drive from the left dlPFC to the right superior parietal lobule (p = 0.005), implicating FPN-to-DAN reorganization. In the discovery arm, 14 miRNAs were nominally differentially expressed (p < 0.05, uncorrected; none survived false-discovery-rate correction), dominated by upregulation of the plasticity-associated let-7 and miR-30 families. Linking the arms, the strongest molecular–connectivity correlations (|r| = 0.90–0.93) fell on FPN-to-DAN and SN-to-DMN edges, consistent with normalization of the pathological DMN–DAN anticorrelation in TRD. Together these results provide the first evidence of coupled plasma miRNA and directed multi-network connectivity changes following rTMS in TRD, identifying candidate molecular correlates of a three-component network reorganization. Replication in larger, sham-controlled samples is required.</p>