HDtDCS in Logopenic Variant PPA: Effects on Language and Neural Mechanisms

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.