The effects of transcranial direct current stimulation techniques to modulate resting-state EEG and reduce SOL: A randomized controlled trial.

Objective: To investigate the effects of repetitive bilateral transcranial direct current stimulation (tDCS) on sleep of latency (SOL) and resting-state electroencephalography (EEG) in individuals. Methods: Twenty-eight young adults, aged 21-25 years, with a mean of 22.96 ± 0.87 years, were recruited and randomly grouped into an experimental group(13 people) and a control group (15 people). Subjects in the experimental group received five awake-phase resting-state tDCS over a one-week period, with anodes placed bilaterally in the dorsolateral prefrontal cortex (F3, F4) and cathode in the left upper arm. The current intensity was 1.5 mA, and the stimulation time was 15 min. The control subjects received pseudo-stimulation, with only the beginning and end of the stimulation for 30 s to receive a gradual rise and fall of the current. The intermediate current intensity was 0 mA, and the rest of the treatment parameters and processes were the same as those in the experimental group. All subjects filled out a sleep diary every day during the experiment. Results: Compared with the pre-intervention period, in the subjective scale results, the sleep of latency factor score in the subjective sleep quality assessment scores of the subjects in the experimental group was significantly lower (p = 0.001); in the EEG results, the theta band power in the midline regions of the brains of the subjects in the experimental group (especially in the central Cz location and the prefrontal cortex) was significantly elevated, whereas the control group did not show such a difference. Conclusion: Transcranial direct current stimulation can significantly reduce the sleep of latency of individuals and enhance theta band power to promote changes in the brain from wakefulness to drowsiness, thus enhancing sleep quality. This enhancement may be due to enhancement of inhibitory executive function. In the future, neuromodulation technology is expected to be applied to insomnia patients, especially those whose main symptom is difficulty falling asleep.