Neurobehavioral Mechanisms of Choice in Opioid Use Disorder

Inclusion Criteria: * Must meet moderate/severe criteria for moderate/severe opioid use disorder, report recent prescription or illicit opioid use, and be opioid dependent, as evidenced by either a urine sample positive for recent opioid use or being in frank withdrawal during screening. * Female subjects must be using an effective form of birth control (e.g., birth control pills, surgical sterilization, IUD, cervical cap with a spermicide, or abstinence). * Able to speak and read English * Subjects who are interested in completing the remifentanil dose-ranging session must report a history of intravenous opioid use and a baseline O2 saturation of 95% or greater. Exclusion Criteria: * History of, or current, clinically significant physical disease (e.g., respiratory disease \[asthma, COPD, sleep apnea\], impaired cardiovascular functioning, seizure disorder or CNS tumors) or current or past history of psychiatric disorder that would limit compliance in the studies, other than substance use disorder. * Meet diagnostic criteria for psychoactive substance use disorder for substances other than opioids (OUD subjects only) or nicotine that would require detoxification (i.e., alcohol, benzodiazepines or barbiturates). * Contraindications for MRI scanning (e.g., pacemaker, metal implants, claustrophobia, or any other implanted medical device). * Vision or hearing problems that would preclude completion of experimental tasks. * At risk for respiratory complications and have predictors of difficult bag mask ventilation (e.g., dentures, very full beard), in case emergency respiratory intervention is needed. * Seeking treatment for SUD. * Poor venous access (only subjects who will participate in the remifentanil dose-ranging session).