RecruitingBehavioural interventionAutobiographical Memory in Opioid Use DisorderThe research study is being conducted to better understand memory function in people with opioid use disorder (OUD) and whether memory training can improve the symptoms and lives of people with OUD. Further, this study seeks to identify how brain and heart activity contribute to memory function and OUD symptoms. Participants will be asked to complete a baseline assessment, four weeks of at-home memory training (MemFlex), and a post-treatment follow-up assessment. Everyone enrolled will receive MemFlex as there is no placebo group. Each visit will include collection of a urine sample for drug testing. During the baseline and follow-up assessments, researchers will collect brain information using functional near-infrared spectroscopy (fNIRS) and heartbeat data using a wearable wristband sensor. MemFlex is a cognitive-behavioral intervention that does not pose any risk. However, the use of MemFlex in this study is experimental as it has not been tested in individuals with OUD. We will enroll 20 participants with OUD and 10 participants meeting healthy volunteer criteria.