Transcranial Direct Current Stimulation in the Treatment of Primary Progressive Aphasia

Inclusion Criteria: * Presence of aphasia attributable to non-fluent PPA or logopenic PPA * High school education (or more) * Between the ages of 50 and 90 * Must be able to understand the nature of the study and give informed consent Exclusion Criteria: * Cognitive impairment of sufficient severity to preclude giving informed consent (Mini Mental State Examination \[MMSE\] less than 15) * Any unrelated neurologic or physical condition that impairs communication ability * History of unrelated neurological conditions, including but not limited to traumatic brain injury (TBI), stroke, or small vessel disease, that has resulted in a neurologic deficit * Any additional neurological condition that would likely reduce the safety of study participation, including central nervous system (CNS) vasculitis, intracranial tumor, intracranial aneurysm, multiple sclerosis, or arteriovenous malformations * A medically unstable cardiopulmonary or metabolic disorder * Individuals with pacemakers or implantable cardiac defibrillators * Terminal illness associated with survival of less than 12 months * Major active psychiatric illness that may interfere with required study procedures or treatments, as determined by the enrolling physician * Current abuse of alcohol or drugs, prescription or otherwise * Participant in another drug, device, or biologics trial within 30 days prior to enrollment * Nursing a child, pregnant, or intending to become pregnant during the study * Left-handedness Exclusion for tDCS, specifically: * History of spontaneous or partial complex seizures or unexplained loss of consciousness within 6 months of enrollment * Subjects with metallic objects in the face or head other than dental apparatus, such as braces, fillings, or implants * Subjects with previous craniotomy or any breach in the skull Exclusion for MRI, specifically: * Presence of any of the following devices: cardiac pacemaker, other pacemakers (for carotid sinus, insulin pumps, nerve stimulators, lead wires or similar wires), optic implant, implanted cardiac defibrillator, aneurysm clip, any electronically/magnetically/mechanically activated implant, ferromagnetic implants (coils, filters, stents; metal sutures or staples) * Presence of any of the following: pregnancy, claustrophobia, metal in eye or orbit, tattooed eyeliner