High-gamma tACS may regulate brain network connectivity to alleviate symptoms in female adolescent non-suicidal self-injury: a preliminary TMS-EEG pilot study

Abstract Objectives To explore the efficacy and potential neurophysiological mechanisms of 77.5 Hz transcranial alternating current stimulation (tACS) in the treatment of female adolescent non-suicidal self-injury (NSSI). Methods Six female NSSI patients received 21 days of 77.5 Hz, 15 mA tACS treatments. Neuropsychological scales were assessed at baseline (W0), after treatment (W3), and 4-week (W7) and 8-week (W11) follow-ups. Transcranial magnetic stimulation with EEG evaluated changes in source-level brain activity and phase-synchronous functional connectivity. Mixed repeated-measures ANOVA with Bonferroni correction (p < 0.017) was used for behavioral data analysis to correct for multiple comparisons. Effect sizes (Cohen’s d) was reported for all statistical results. Results Significant improvements were observed in depressive symptoms and self-injury behaviors after treatment (OSIC: W7: P = 0.009, Cohen’s d=-1.682; HAMD-24: W3: P = 0.006, Cohen’s d=-1.892; W7: P = 0.001, Cohen’s d=-2.839; W11: P = 0.001, Cohen’s d=-2.738; all P < 0.017). Electrophysiological analysis revealed that 77.5 Hz tACS might decrease Default network activity, increased Limbic, SalVAttn and Control network activity, and enhanced the functional connectivity in high-gamma band between Control and SalVAttn/Default network. A positive correlation was found between increased C100 activity in the SalVAttn (left frontal-insula) region and reduced HAMD-24 scores (R = 0.826, p = 0.043), this correlation analysis was based on a small sample size (n = 6), and the correlation coefficient was unstable, with results only for preliminary exploratory reference. Conclusion 77.5 Hz tACS may alleviate NSSI symptoms in female adolescents potentially by regulating brain activity and functional connectivity in emotional-control networks.