The purpose of this study is to develop a technique called real time fMRI neurofeedback.

This technique uses a regular MRI scanner, except that special software allows the researchers to measure activity in participants brain, using fMRI, and then give information, in the form of a feedback signal, which indicates brain activity in real time, while in the MRI scanner. The larger goal of this study is to develop ways to help people, including those with depression, better regulate brain activity. The researchers think that this may be helpful in managing psychiatric symptoms.

This study design has three phases, however, only two phases (phase 2 and 3) are considered to be a clinical trial. Phase 2 (part 2) was registered and is NCT05934604. This is the phase 3 (part 3) for this project and is funded by the National Institutes of Health.

Part 3/Phase 3 study hypothesis are:

• Rest Focus Task (RFT) will activate brain networks at the individual subject level to provide a viable signal for Neurofeedback (NF)
• At the group level, RFT in the Active>Passive contrast will activate canonically defined salience network
• Neurofeedback-reinforced practice over the session will increase RFT activation over the course of the training session, comparing RFT activation, without NF, before and after NF runs.
• Valid Neurofeedback will increase RFT activation more compared to sham NF (assessed during the no-NF session).

Inclusion Criteria:

• Meets The Diagnostic and Statistical Manual of Mental Disorders five (DSM5) criteria for Major Depressive Disorder, single or recurrent, active or in partial remission
• Patient Health Questionnaire (PHQ9) greater or equal (≥)6, and approximately (~) 50% with PHQ9≥10
• If participants are taking antidepressant medications, on stable dosage for 4 weeks
• No history of active substance use disorder in the past 6 months
• Absence of suicidal thoughts with plans or intentions, as assessed by Columbia Suicide Severity Rating Scale (C-SSRS)
• If a woman of child-bearing age, not pregnant or trying to become pregnant
• Ability to tolerate small, enclosed spaces without anxiety
• No metals, implants or metallic substances within or on the body that might cause adverse effects to the subject in a strong magnetic field, or interfere with image acquisition, e. g. aneurysm clips, retained particles (for example metal workers with exposures, protocol has more details), etc.
• Size compatible with scanner gantry (per protocol)
• Ability and willingness to give informed consent to participate.

Exclusion Criteria:

• Size not compatible with scanner
• Not meeting diagnostic criteria for bipolar disorder, schizophrenia, other psychosis, obsessive-compulsive disorder, active eating disorder or Post-traumatic stress disorder (PTSD)
• No history of serious neurological illness (including, but not limited to, seizures/epilepsy) or current medical condition that could compromise brain function, such as liver failure
• No history of closed head injury, e. g. loss of consciousness > ~5 min, hospitalization, neurological sequela