Transcranial Direct Current Stimulation and Extinction in Obsessive Compulsive Disorder

Inclusion Criteria: * All Participant Inclusion Criteria would include: 1. 18 years of age or older 2. speak English fluently, and 3. able to provide written and verbal informed consent. * Obsessive-compulsive disorder (OCD) Inclusion Criteria would include: 1. meet criteria for OCD as determined by structured clinical interview 2. exhibit significant current symptoms of OCD 3. report duration of OCD symptoms of at least 1-year 4. OCD symptoms are primary or co-primary relative to other psychiatric diagnoses 5. stable psychiatric treatment (≥8-weeks) or no active treatment. 6. exhibit significant current symptoms of OCD as determined by the Dimensional Obsessive-Compulsive Scale (DOCS) (≥18). Exclusion Criteria: * All Participant Exclusion Criteria would include: 1. active severe substance use disorder(s) 2. acute suicidality 3. history of bipolar or psychotic disorder(s) 4. significant developmental disabilities 5. loss of consciousness \> 10 minutes 6. history of traumatic brain injury 7. major neurological disease 8. a positive pregnancy test 9. other brain stimulation or magnetic resonance imaging contraindications 10. new psychological treatment within the past 8 weeks 11. daily anxiolytic medication use (e.g., benzodiazepine). * Non-Clinical Control Exclusion Criteria would include: 1. meet current criteria for a psychiatric disorder as determined by structured clinical interview 2. active-psychotropic medications.