Optimizing Targeted Interventions for Aphasia

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Language treatments for chronic aphasia are not restorative, and the psychosocial and economic impacts of aphasia are devastating. Knowledge of modifiable brain targets has not been harnessed to catalyze meaningful treatment outcomes. Transcranial direct current stimulation (tDCS) allows systematic investigations of the effects of brain target engagement. tDCS investigations aim to restore a left hemisphere bias for language processing. tDCS has strong clinical translational potential, but the diffuse current flow it delivers to the stroke brain and uncontrolled cortical dosage limits inferential precision. Although tDCS could be used to shape hemispheric contributions to language and investigate target engagement, methodological approaches so far have not employed it for that purpose, preventing vertical progress in aphasia treatment development. Both aphasia and tDCS research are lacking data on meaningful language outcomes and treatment-induced brain changes. There is a critical need for rigorous investigations of treatments capable of coaxing spared brain areas into adaptive participation for functional improvements. Failure to meet this need means that millions of people with aphasia will have little hope for easing of disability burden. The long-term goal is to optimize aphasia recovery with clinically translatable brain-based approaches. The overall objective of this project is to determine how to induce functional language improvement and adaptive changes to spared eloquent language cortex. The central hypothesis is that functional language outcomes for people with chronic aphasia will be enhanced when treatment focuses on normalizing language processing bias to the left hemisphere. The rationale is that identifying behavioral and adjunctive treatments that engage brain targets will allow optimization of treatment parameters and facilitate the development of novel and personalized approaches to move beyond the status quo and towards precision neurorehabilitation. Guided by strong preliminary data, this hypothesis will be tested by pursuing two specific aims: 1) Demonstrate the enhancing effect of targeted right hemisphere modulation; and 2) Measure normalization of brain activity following treatment. Under the first aim, language treatment will be paired with active or sham HD-tDCS to inhibit right inferior frontal right gyrus (pars triangularis), after which gains in narrative and naming will be measured and the two groups compared. Under the second aim, changes in EEG measures of brain function will be characterized and related to narrative and naming outcomes. This contribution will be significant because it is expected to have broad application to clinical populations who would benefit from treatment-induced adaptive brain reorganization. Our major innovation for this project is the pairing of a proven behavioral treatment that will recruit language networks with targeted “high-definition” tDCS (HD-tDCS) to focus inhibition and control cortical dosage to the frontal right hemisphere. These contributions will be important for the more than 2.4 million adults in the United States living with aphasia.