Cognitive Enhancement in Recurrent Depression (The COG-D-R Study)

The goal of this clinical trial is to learn if a combination of non-drug treatments works to benefit memory, thinking, and brain functioning in older individuals with recurrent depression. The non-drug approaches the investigators are studying include transcranial direct current stimulation (tDCS) and computerized cognitive training. tDCS uses small currents of electricity on the forehead to potentially stimulate your brain's ability to process and learn. Computerized cognitive training uses tablet games to improve memory and thinking. In this study, two different cognitive training programs are being investigated, both of which are stimulating and designed to engage brain activity. One that is believed to be a specific treatment for depression, while the other provides extra stimulation for the brain that is non-specific. Two different tDCS parameters - active stimulation and sham (or placebo) stimulation - are also being investigated. Participants will be randomized to one of three study groups: 1. Depression cognitive training treatment with active brain stimulation 2. Depression cognitive training treatment with sham brain stimulation 3. Non-specific cognitive training treatment with sham brain stimulation The main questions this clinical trial aims to answer are: * Does "depression cognitive training treatment with active brain stimulation" benefit thinking and memory more so than the other treatments? * Does "depression cognitive training treatment with active brain stimulation" benefit brain functioning more so than the other treatments? Participants will: * Complete several baseline and post-intervention visits at the research center for checkups and tests over the course of 3-4 months. * Visit the research center daily for 4 weeks to complete their assigned treatment.