Reductions in GABA following a tDCS-language intervention for primary progressive aphasia

• Published in: Neurobiology of aging 2019-07, Vol.79, p.75-82
• Main Authors: Harris, Ashley D., Wang, Zeyi, Ficek, Bronte, Webster, Kim, Edden, Richard AE, Tsapkini, Kyrana
• Format: Article
• Language: English
• Subjects: Aged; Anodal tDCS; Aphasia, Primary Progressive - metabolism; Aphasia, Primary Progressive - psychology; Aphasia, Primary Progressive - therapy; Female; Follow-Up Studies; GABA-edited MRS; gamma-Aminobutyric Acid - metabolism; Humans; Language Therapy; Learning; Magnetic Resonance Spectroscopy; Male; Middle Aged; Neural plasticity; Neurodegenerative disorder; Neuronal Plasticity; Time Factors; Transcranial Direct Current Stimulation
• ISSN: 0197-4580; 1558-1497
• DOI: 10.1016/j.neurobiolaging.2019.03.011

Transcranial direct current stimulation (tDCS) has shown efficacy in augmenting the effects of language therapy in primary progressive aphasia (PPA). The mechanism of action of tDCS is not understood, but preliminary work in healthy adults suggests it modulates γ-aminobutyric acid (GABA) levels to create an environment optimal for learning. It is unknown if this proposed mechanism translates to aging or neurodegenerative conditions. This study tested the hypothesis that tDCS reduces GABA at the stimulated tissue in PPA. We applied GABA-edited magnetic resonance spectroscopy to quantify GABA levels before and after a sham-controlled tDCS intervention with language therapy in PPA. All participants showed improvements but those receiving active tDCS showed significantly greater language improvements compared to sham both immediately after the intervention and at 2-month follow-up. GABA levels in the targeted tissue decreased from baseline after the intervention and remained decreased 2 months after the intervention. This work supports the hypothesis that tDCS modulates GABAergic inhibition to augment learning and is clinically useful for PPA combined with language therapy. •Anodal tDCS augments language therapy in patients with PPA compared with sham-tDCS.•Transcranial DCS decreases GABA in the left IFG, the tissue local to the tDCS anode after the intervention.•Improvements in language scores are better maintained with active tDCS at 2-month follow-up.•GABA remains lower in the targeted tissue (left IFG) in the anodal tDCS group at 2-month follow-up.