The design is primarily a randomized control-trial design, comparing the effects of placebo (sham) and active TMS stimulation on reward processing across two groups of participants - healthy controls and opioid users.~Participants will be asked to engage in a virtual T-maze task, a reward-based choice task that elicits robust reward positivities. During this task participants will receive simultaneous EEG/TMS, while they engage in the virtual T-maze decision making task, used in our previous reward positivity studies on SUDs. ERPs will be recorded throughout the T-Maze task, and the reward positivity will be measured as the difference in maximum amplitude between reward and no-reward feedback conditions.~The TMS coil will be positioned using a an Adept Viper s850 robotic arm (SmartMove, ANT Neuro, Enschede, The Netherlands), providing precise targeting of the predetermined left dorsolateral prefrontal (DLPFC) coordinate (< 10 mm from the scalp, orientated at a 45º angle). Participants in the active TMS condition will receive rTMS pulses throughout the duration of the T-Maze task, with a maximum of 2000 pulses delivered to each participant. Identical parameters will be applied to the SHAM group with the exception that the TMS coil will be flipped 180º to mimic auditory stimulation.
The primary aims of this study are to identify impaired cognitive control in opioid use disorder (OUD) and subsequently to examine the effects of transcranial magnetic stimulation (TMS) on reward processing, as measured by the reward positivity (an electrophysiological signal) in people with OUD. To this end, the investigators will adopt a randomized sham-controlled trial to evaluate the efficacy of Ri-TMS on cognitive control in OUD.~The investigators hypothesize that Ri-TMS will be successful in modulating the reward positivity in opioid users in the active TMS condition.