Existing treatments for mood disorders usually take weeks to months to achieve their antidepressant effects, and a significant number of patients do not respond. Moreover, during the early phase of treatment, increased risk of suicide attempts is a major concern. Thus, pharmacological interventions that exhibit antidepressant effects within hours or a few days are urgently needed. The rapid-acting antidepressant effects of a commonly used surgical anesthetic, Ketamine, were recently realized. However, much remains unknown with regard to changes in cognition that occur after an administration of Ketamine. Prior research has suggested a bias to negative memories in depression and a bias to positive memories in healthy controls. Additionally, hyper-connectivity within the brain's resting state network, the default-mode network, has been associated with depressive rumination. The present study examines changes in memory biases and brain network connectivity resulting from an administration of Ketamine in patients with treatment-resistent mood disorders.