Additional Study Information: We will evaluate the D-cycloserine (DCS) and lurasidone with MRI measurement of brain responses to DCS. DCS is a drug that works on the same brain receptor as ketamine. DCS is not approved by the FDA for bipolar depression. Study participants will receive a dose of lurasidone or placebo in one MRI and a dose of DCS in another, followed by an optional follow-up four week phase of lurasidone plus DCS. We hope to develop a better understanding of how these medications work. Participants should be currently depressed and be willing to stop their medications or not currently be taking any medications. Participation involves clinical assessments, taking medications, blood draws and up to 3 MRIs. Eligible individuals will be compensated up to $1100 and may receive up to 5 months of free doctor visits for medication-based treatment.