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

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.