40 Hz Transcranial Alternating Current Stimulation for Inducing Gamma Oscillations

Working Memory behavioral performance

Participants view a continuous sequence of alphabet letters, presented as stimuli in Arial font, size 120pt, on a tube screen positioned at 60cm eye distance. The stimuli are shown with a time interval of two seconds between them. The task consisted of six blocks with 70 stimuli, including 12 possible hit trials. Participants were instructed to press the left key on a response box if the presented stimulus matched either the one presented one trial prior (1-Back) or three trials prior (3-Back). In all other cases, participants press the right key. The left button is pressed with the index finger, while the right button is pressed with the middle finger of the right hand, with buttons aligned horizontally. The response condition varied by block, with three blocks for 3-Back and three for 1-Back, and the order was counterbalanced across participants and sessions.

Time frame: During procedure (20 minutes)

electroencephalogram (EEG) oscillatory power

Change in the EEG power in the gamma band

Time frame: up to 2 hours after the intervention

electroencephalogram (EEG) functional connectivity

Change in EEG functional connectivity, specifically global efficiency, coherence, and phase-locking value at gamma frequency

Time frame: up to 2 hours after the intervention