All intervention sessions will use the Soterix Mini-CT Remote tDCS device

We will deliver 2-mA tDCS current intensity during a 30 minute stimulation period (including a 30-second ramp-up and 30-second ramp-down period) to the dorsolateral prefrontal cortex. Electrodes will be fixed on marked locations based on the 10-20 EEG system. Anodal stimulating electrode will be over the left DLPFC (F3) and cathodal electrode over the right DLPFC (F4).

To assess changes in target engagement, we will measure the change in resting-state functional connectivity (measured as a Pearson correlation coefficient, r) between the prefrontal cortex and the incentive salience network from pre- to post-intervention using a paired t-test. The connectivity metric ranges from a minimum value of -1.0 (perfectly negative correlation) to a maximum value of 1.0 (perfectly positive correlation). Higher scores indicate stronger functional connectivity (greater top-down regulation), representing a better outcome.

To assess changes in executive functioning, we will measure the change in executive functioning from pre- to post-intervention using a repeated measures t-test. Cognitive performance will be assessed via a behavioral battery spanning cognitive flexibility, working memory, inhibitory control, and delay discounting (utilizing standardized Pearson assessments and a computerized delay discounting task). Performance metrics across tasks will be converted to standardized z-scores (typically ranging from -3.0 to +3.0). The primary endpoint is the post-intervention mean z-score minus the pre-intervention mean z-score. A positive change score indicates an increase in executive functioning, representing a better clinical outcome.