Stratified Pharmacological Approaches for Regulating Circuit-Level Effects

Inclusion Criteria:

* 18-65 years old (inclusive)
* Fluent and literate in English, with non-impaired intellectual abilities to ensure adequate comprehension of the task instructions.
* Willing to provide written, informed consent.
* Functional magnetic resonance imaging (fMRI) scanning eligibility. All participants will need to successfully complete the screening forms at the Stanford Center for Cognitive and Neurobiological Imaging (CNI).
* Patient Health Questionnaire-8 (PHQ-8) \>/= 10
* Meet the Diagnostic and Statistical Manual of Mental Disorders-5 (DSM-5) diagnostic criteria for current or recurrent nonpsychotic Major Depressive Disorder (MDD) established by the Mini International Neuropsychiatric Interview (MINI)

Exclusion Criteria:

* Suicidality with active plan or as determined clinician judgment
* Current or lifetime history of medical illness or brain injury that may interfere with assessments as determined by clinician judgment
* Severe impediment to vision, hearing, and/or hand movement likely to interfere with ability to complete the assessments, or is unable and/or unlikely to follow the study protocols as determined by clinician judgment
* Pregnant, breastfeeding or unwilling or unable to use adequate birth control throughout the study
* History of non-responsive depression to dopamine agonists
* Any contraindication to being scanned in the 3.0T fMRI scanner, such as a cardiac pacemaker or implanted device that has not been cleared for scanning
* Previous or current DSM-5 bipolar disorder (I, II, not otherwise specified), schizophrenia spectrum or other psychotic disorders, or psychosis or as determined by clinician judgment
* Previous or current diagnosis of Attention-Deficit/Hyperactivity Disorder (ADHD)
* Meeting DSM-5 criteria for current Obsessive-Compulsive Disorder (OCD) or eating disorder
* Meeting DSM-5 criteria for alcohol use disorder or substance use disorder within the last 12 months
* Clinically significant presence/history of impulsive-compulsive behaviors or control disorder including but not limited to gambling disorder within the last 12 months.
* Current use or use of psychotropic medication within the past month. (If the participant's usual treating clinician agrees with discontinuing the medication, participants may enroll after tapering off the medication under the supervision of either their usual clinician or the study clinician. A washout period of 5 half-lives-or a different duration as determined by the study clinician-must be completed before the first scan.)
* Concurrent participation in other intervention or treatment studies