Using Combined EEG and Non-invasive Brain Stimulation to Examine and Improve Reward Functioning in Opioid Use Disorder

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.

Inclusion criteria

• Native English speakers
• Males and Females aged 18-55 years old
• Ability to provide informed written or verbal consent
• Opioid dependent individuals (according to the Alcohol, Smoking and Substance Involvement Screening Test opioid dependence score), or
• Healthy controls with no history of significant substance use

Exclusion criteria

• Un-correctable visual impairment
• Uninterruptable central nervous system medication
• TMS contraindications (e.g., pregnancy, braces, history of seizures, metal implants).
• History of neurological or psychiatric illness
• Diagnosed learning disability
• History of significant head injury (loss of consciousness for more than five minutes)
• Substance abuse (Participants who score above 39.5 on the Global Continuum of Substance Risk scale of the Alcohol, Smoking and Substance Involvement Screening Test - controls only)
• Use of psychoactive or vasoactive medications