An EEG Study of Intravenous Ketamine for Major Depression Disorder

Inclusion Criteria: 1. Individuals between 18 and 70 years of age, inclusive 2. Adult patients with a documented primary Axis I clinical diagnosis meeting criteria from the DSM-V for a major depressive disorder 3. Score of \<15 on the DES 4. Moderate to severe symptoms objectively documented using MADRS total score of ≥ 20 5. Ability to maintain scheduled appointments for screenings, 4 treatment visits and follow-up EEG visit. 6. History of major depressive disorder. 7. Females of child-bearing potential who are sexually active must agree to use two forms of contraception. A pregnancy test will be performed before the first treatment. 8. Must have stable residence address, internet and mobile phone. 9. Must speak fluent English. Exclusion Criteria: 1. Known allergy to ketamine or any other drug used in the study. 2. Use of ketamine in a therapeutic model within the preceding 12 months of the study. 3. Current or any history of schizoaffective disorder(s). 4. Score of ≥ 15 on DES 5. History of illicit active substance abuse or dependence including ketamine as determined on by the SCID-5-CT and/or drug urine screening during study visits. 6. Pregnancy, breastfeeding or desire to become pregnant during the course of the study. 7. Serious, unstable illnesses including, but not limited to; hepatic, gastro-intestinal, respiratory, cardiovascular (including ischemic heart disease and coronary heart disease). History of ischemic stroke, atrial fibrillation, severe endocrinological, neurological, immunological or hematological disease. 8. Any history of cerebral vascular events including stroke, bleeding into the brain and subdural hematomas. 9. Any implantable metallic device(s) or implant(s) above the level of shoulders. 10. Any non-removable metallic piercings. 11. Patients with cochlear implants and non-removable hearing aids. 12. Current use of: Dilantin, Depakote, Phenobarbital, Gabapentin, Pregabalin and Benzodiazepines. Certain candidates with long use of Benzodiazepines may qualify at PI's discretion. 13. Severe labile hypertension. 14. Significant uncontrolled hypertension (i.e., SBP \> 150 mmHG, DBP \> 100 mmHG) 15. Uncontrolled diabetes mellitus. 16. Patients on renal dialysis. 17. Inability to achieve consistent IV access.