PROJECT SUMMARY: Opioid Use Disorder (OUD) stands out as being the most lethal of addictions. Not only is there a significant risk of overdose, the life span of a patient with OUD decreased by about 18 years compared to those without an addiction. Yet, at the same time, there are three FDA approved medications available to treat OUD: methadone, buprenorphine, and naltrexone. While these medications are helpful for treating OUD, the majority of patients do not experience long term remission. Our goal is to develop an adjunctive treatment for OUD, using brain stimulation to improve treatment response. Our device, called On-Demand Electrostimulation (ODE) is designed to stimulate the brain regions that have been implicated in OUD. Previous imaging studies show that the sections of the prefrontal cortex are associated with inability to exert cognitive control over drug seeking behavior. These regions include the dorsolateral prefrontal cortex (dlPFC), dorsomedial prefrontal cortex (dmPFC), and anterior cingulate (ACC). Previous imaging studies in OUD also show that these brain regions are hypoactive in OUD. Thus, our goal is to stimulate these brain regions using ODE. In this phase one application, we delineate the initial steps needed for the development of ODE. This includes brain simulation studies and bench work using human skulls (as phantoms) to measure the electrical field generated by our electrodes. The simulation studies will be performed using a brain model that was developed in collaboration with the FDA for device development. The skull studies will be used to investigate the degree of stimulation generated by the electrodes themselves. At the end of phase one, our goal is to have a completed validation and verification plan in place with the FDA.