Combined tDCS and Cognitive Training as an Adjunctive Treatment in Opioid Use Disorder

Primary outcomes

1. tDCS effect on circuit-based target engagement of a prefrontal-incentive salience network

   Time frame: immediately after the intervention

   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.

2. tDCS effect on executive functioning

   Time frame: immediately after the intervention

   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.