Modulating Default and Salience/Ventral Attention Networks: Exploring the Treatment Effect of Transcranial Alternating Current Stimulation on Chronic Insomnia

INTRODUCTION: Chronic insomnia necessitates novel therapeutic strategies. While transcranial alternating current stimulation (tACS) shows promise, its neural mechanisms remain elusive. METHODS: We conducted a 4-week, double-blind, randomized, sham-controlled trial to investigate the effects of high-intensity tACS (15 mA). Eighteen patients completed the protocol and longitudinal resting-state fMRI. RESULTS: Clinical results demonstrated a significant reduction in Pittsburgh Sleep Quality Index (PSQI) scores within the active tACS group (13.8 [3.0] vs. 7.7 [3.0], p < 0.001), indicating substantial clinical improvement, whereas the sham group showed no significant change (13.8 [2.9] vs. 13.9 [2.4], p = 0.74). Furthermore, the spontaneous brain activity exhibited extensive reductions in both the Default and Salience/Ventral Attention networks, showing a negative correlation with increase in clinical sleep scores. The functional connectivity was significantly altered within the Default and Salience/Ventral Attention networks, and the majority of changes displayed a decreasing trend. Graph theoretical analysis revealed a topological reorganization in these networks, characterized by reduced clustering coefficients and characteristic path lengths, coupled with increased global efficiency. CONCLUSION: The study provides valuable insights into the potential mechanisms of tACS as an innovative intervention for improving sleep quality in insomnia, contributing to further research and optimization for insomnia treatment.