This study aims to evaluate the effectiveness of a therapy called High-Definition Transcranial Direct Current Stimulation (HD-tDCS) for the treatment of the language deficits experienced by people with a type of Primary Progressive Aphasia. This study uses a combination of brain imaging, language assessment, language training sessions, and HD-tDCS therapy as well as placebo therapy sessions.

The logopenic variant of Primary Progressive Aphasia (lvPPA) is an untreatable neurodegenerative disorder that is often referred to as the 'language form' of Alzheimer's Disease (AD). Transcranial Direct Current Stimulation (tDCS) has emerged as a safe and potentially effective tool that appears to enhance language production when delivered during language training. This technology provides a critical opportunity to conduct disease intervention.

In this study, the investigators will test the hypothesis that High-Definition tDCS (HD-tDCS) will improve performance on language tasks by increasing functional connectivity and by regulating abnormal neuronal oscillatory patterns. The rationale for this project is that a determination of the therapeutic efficacy and the associated neural mechanisms of HD-tDCS in lvPPA is likely to offer a scientific framework whereby new stimulation parameters, conditions, and target sites can be deciphered.

This study will test the hypothesis that HD-tDCS will improve performance on language tasks by increasing functional connectivity and by regulating abnormal neuronal oscillatory patterns. The language performance and functional connectivity changes will be determined in a randomized, double-blind, sham-controlled crossover manner, in which a stimulation of up to 2mA in the targeted cortical tissue or sham is administered to 20 lvPPA subjects age 45 years and older. The order of treatments is counterbalanced in a within-subject crossover design. In brief, study participants will receive sham during one treatment period and stimulation during the other treatment period.

Inclusion Criteria:

• Diagnosed with language variant Primary Progressive Aphasia (lvPPA) subtype, defined as either clinical lvPPA or imaging-supported lvPPA in accordance with the most recent diagnostic criteria (Mesulam., 2001; Gorno-Tempini et al., 2011).
• Fluent in English.
• 45 years of age or older.
• Structural brain MRI performed within 3 years prior to enrollment.

Exclusion Criteria:

• Severe cognitive, auditory or visual impairments that would preclude cognitive testing.
• Presence of major untreated or unstable psychiatric disease.
• A chronic medical condition that is not treated or is unstable.
• The presence of cardiac stimulators or pacemakers.
• Any metal implants in the skull
• Contraindications to MRI
• History of seizures
• History of dyslexia or other developmental learning disabilities.

Informed consent through study completion, approximately 28 weeks.

Safety Population included all subjects who received at least one intervention.

An unblinded member of the study team will randomize participants to the treatment conditions. Study Group assignment will be based on random number generation (in blocks of 4) followed by the creation of numbered envelopes.

Participants and the study team members involved in language training, tDCS delivery, and assessment of outcomes will be blind to the treatment received.