Efficacy and Safety of Task-specific, Biomarker-driven, HD-ctACS inTRD.

Participants received High-Definition closed-loop transcranial Alternating Current Stimulation (HD-ctACS) for 30 minutes daily, 5 days per week. A 4x1 ring electrode montage was used, with the center electrode placed over the bilateral temporal cortices. Stimulation was delivered as a sinusoidal alternating current at a 2 mA peak amplitude, with the frequency individualized for each participant based on their baseline EEG. The stimulation was administered in a closed-loop, task-specific manner: a 500 ms burst of stimulation was triggered only when a subliminal negative facial stimulus was presented and the participant's real-time Nucleus Accumbens gamma power exceeded their baseline by two standard deviations.

Participants received High-Definition transcranial Alternating Current Stimulation (HD-tACS) in 30-minute sessions once daily, 5 days per week. A 4x1 ring electrode layout was used to target the bilateral temporal cortices. The stimulation consisted of a sinusoidal alternating current with a 2 mA peak intensity, delivered at an individualized gamma frequency determined from a baseline EEG. The intervention was administered using a closed-loop, task-specific paradigm: upon presentation of a subliminal negative facial stimulus while the real-time Nucleus Accumbens gamma power exceeded a baseline threshold of +2 SD, a 500 ms stimulation was delivered following a random delay of 1000-2000 ms.