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.

Inclusion Criteria: * Age \> 60 years * Evidence of executive dysfunction via SUBJECTIVE COMPLAINTS (At least one subdomain of the Behavior Rating Inventory of Executive Function in Adults (BRIEF-A) at T \> 65, or At least one average score of \> 1.5 on Planning, Organization, or Attention subdomains of the Everyday Cognition Scale (ECog)) or OBJECTIVE PERFORMANCE (At least one demographically adjusted z-score \> -1.0 SD below the mean on a measure of executive functioning (Digits backward, Trails B, or total Verbal Fluency) on the National Alzheimer's Coordinating Center (NACC) Uniform Data Set 3.0). * DSM-5 diagnosis of a current or past (within last 3 years) depressive episode (e.g., Major Depressive Disorder (MDD), Persistent Depressive Disorder (PDD)) via the using the Structured Clinical Interview for DSM-5 Disorders (SCID-5). * Presence of 2 or more lifetime depressive episodes to be considered "recurrent." * Either stable antidepressant regimen for at least 6 weeks or no current antidepressant treatment (no plans to change treatment over course of study). * Fluent in English Exclusion Criteria: * Other psychiatric conditions via the SCID-5 (including history of bipolar disorder and psychosis, excluding comorbid anxiety disorders) * Severe depression (MADRS score \> 29) * Acute suicidality on clinical evaluation by study clinician and via response on MADRS item 10 (score of 4 or more would require further assessment) * Acute grief (occurring within past month) * History of alcohol use disorder or substance use disorder of moderate or greater severity in the last 12 months * Medications that would significantly interfere with tDCS effects (i.e., sodium channel blockers, GABA-ergic or glutamatergic drugs; see Appendix B for exclusionary list)40 * Primary neurological disorder (e.g., epilepsy, brain tumor, Parkinson's disease, Alzheimer's disease, dementia diagnosis) * Montreal Cognitive Assessment (MoCA) \< 23 * Primary amnestic cognitive profile (\>1.5 SD below demographically-adjusted mean on NACC memory measures in context otherwise normal cognitive profile, or per clinician judgement) * Any physical or intellectual disability affecting ability to complete assessments * Unstable medical illness needing urgent treatment * MRI contraindications * Electroconvulsive therapy (ECT) or transcranial magnetic stimulation (TMS) in last 2 months * Current involvement in psychotherapy * Current involvement in other research studies (including but not limited to: neuromodulation \[TMS or tDCS\] or investigational drug studies). Observational studies \[without intervention\] are acceptable.