The purpose of this research is to learn more about a new treatment for individuals with Major Depressive Disorder (MDD) with heightened symptoms of anhedonia (i.e. loss of pleasure or interest in activities). The treatment is called Prism, and it is a software device intended for a novel form of neurofeedback training to be used in a clinic setting.

During this study, the subject will use different techniques to measure brain activities, including magnetic resonance imaging (MRI) and electroencephalography (EEG).

The study is comprised of the Screening Visit, Baseline Assessment, Pre-training Visit, 20 NF Training Visits (two training visits per week over 10 weeks), two Booster NF Training Visits (Week 16, and Week 20, and the 3-Month Follow-up Assessment Visit (Week 24).

Participants will receive 20 NF sessions.

The study will test the following hypothesis:

• H0: M(Anhedonic)RS-EFP = M(Anhedonic)Sham-EFP
• H1: M(Anhedonic)RS-EFP ≠ M(Anhedonic)Sham-EFP

Where:

M(Anhedonic)RS-EFP and M(Anhedonic)Sham-EFP are the mean changes from baseline HDRS-17 score in the Active and Sham arms of the Anhedonic MDD participants.

*HDRS-21 is administered for cluster analysis

Inclusion Criteria:

1. Primary Diagnosis of MDD with Anhedonia, established according to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition Text Revision (DSM5TR) - HDRS-17 score of ≥20, SHAPS-C score of ≥25.
2. Fluency in written and spoken English.
3. Able intellectually to understand the instructions
4. Ability to give signed, informed consent either written or electronic (via REDCap eConsent).
5. Normal or corrected-to-normal vision and hearing.
6. Ability to adhere to the study schedule.
7. Completed at least one antidepressant treatment course at an adequate dose and duration in the current episode per the ATRQ.

Exclusion Criteria:

1. Contraindications to MRI (e.g., metal in the body, claustrophobia).
2. Any suicidal behavior in the past 1 year (i.e., actual attempt, interrupted attempt, aborted attempt, or preparatory acts or behavior) assessed using Columbia -Suicide Severity Rating Scale (C-SSRS) prior to screening and during the screening period.
3. Diagnosis for current moderate or severe substance or alcohol use disorder (SUD/AUD) within the past month (as defined in DSM-5-substance use disorder).
4. Any unstable medical condition, as per the clinical judgement of the investigator.
5. Any change in, or initiation of, fluoxetine within the past 8 weeks or of other SSRIs/SNRIs antidepressants, bupropion, stimulants, or other psychiatric medications within the past 4 weeks.
6. Recent initiation (within the past 2 months) of psychotherapy; continuation of established maintenance supportive therapy will be permitted.
7. Enrollment in another therapeutic clinical study at screening or within 2 months prior to screening or intended enrollment within the duration of this study.

Double-blind: neither participants nor clinicians assessing them will have information regarding the treatment arm.