Brain Aging and Treatment Response in Geriatric Depression

All subjects will receive 10 to 20mg of escitalopram open-label throughout the trial. Participants will begin taking one 10mg capsule once per day, and this dosage may be increased or decreased depending on the participant's response to the medication. Participants will continue on their assigned dosage of escitalopram until treatment completion.

Memantine dosage will be 5 to 20mg a day. Participants will initially take one 5mg capsule once a day, which will be gradually increased to a maximum of 10mg capsules twice per day.

Placebo pills will be taken in combination with the active Namenda (Memantine) pills. Participants will initially take 1 capsule per day, which will be increased to a maximum of 1 capsule twice per day.