Reward Function and Therapy for Late-Life Depression

Inclusion Criteria: * Age greater than or equal to 60 years. * Diagnosis of unipolar major depressive disorder without psychotic features, determined by Structured Clinical Interview for the Diagnostic and Statistical Manual for Mental Disorders (SCID). * Montgomery-Asberg Depression Rating Scale (MADRS) score greater than or equal to 20. * Mini Mental State Exam (MMSE) score greater than or equal to 24. * Off antidepressants or on a stable dose of an antidepressant for 12 weeks and no intent to change the dose in the next 10 weeks. * Capacity to provide written consent for both research assessment and treatment. Exclusion Criteria: * Intent or plan to attempt suicide in the near future. * Presence of current psychiatric diagnoses other than major depressive disorder without psychotic features, generalized anxiety disorder, or specific phobia. * History of past psychiatric diagnoses other than major depressive disorder without psychotic features or anxiety disorders (separation anxiety disorder, specific phobia, social phobia, panic disorder, agoraphobia, or generalized anxiety disorder). * Use of psychotropic drugs or cholinesterase inhibitors other than use of less than or equal to 0.5 mg of lorazepam daily up to five times per week. * Neurological disorders (dementias, history of stroke, multiple sclerosis, Parkinson's disease, epilepsy, etc.); cardiac, renal, or respiratory failure; severe chronic obstructive pulmonary disease; metastatic cancer; or debilitated states or less common medical illnesses that may either influence neural systems of interest or ability to participate in the study.