Changes in Electrical Brain Activity Due to tDCS in Post-Stroke Chronic Aphasia: a Double-Blind Randomized Controlled Study

Research Objectives To better understand changes in brain activity related to transcranial direct current stimulation (tDCS) in post-stroke chronic aphasia. Design Double-blind randomized placebo controlled study design. Setting Casa Colina Research Institute. Participants Forty three post-stroke outpatients with chronic aphasia (32 males; age: 61±13y; 0.9-18years post-injury; 32 ischemic stroke; 19 non-fluent aphasia). Twenty patients were in the tDCS group. Interventions Participants were randomly assigned either to the tDCS group (cathode on Broca, left side) or to the sham/placebo group. Both groups had five consecutive days of 20 minutes session, using a FDA approved tDCS device (soterixmedical.com). Resting state electrophysiological recordings (5 minutes) and behavioral assessments were performed the week before/after tDCS/sham intervention. Main Outcome Measures 1) EEG data: power spectrum as well as coherence in delta, theta, alpha and beta frequencies in fronto-temporal electrodes; 2) Behavioral data: the Western Aphasia Battery-Revised (WAB-R total scores and subscores). Results For the behavioral data, groups differed, pre/post intervention, on the WAB-R total score (F=5.22; p=0.028) as well as for the Auditory-Verbal Comprehension (F=4.657; p=0.038) and Repetition (F=4.56; p=0.04) subscores. For the EEG, groups also differed, pre/post intervention, when looking at changes in coherence between Broca and Wernicke on the contralateral side (F8T4, alpha and beta) as well as between Broca area on bilateral sides (F7F8, beta) and other fronto-temporal electrodes (F3T3, beta; FzT5, alpha; F4T5, beta). Post-hoc analyses revealed a significant increase in coherence for the tDCS group (but not for the sham group) for the following electrodes: F8T4 (alpha), F3T3 (beta) and F4T5 (beta). Conclusions In this double-blind randomized placebo controlled trial, our findings show a higher improvement in language functions (for both receptive and expressive language skills) in response to treatment as compared to sham. These improvements seem related to an increase in coherence not only in ipsilateral but also contralateral fronto-temporal electrodes, suggesting a higher functional connectivity within the language network due to tDCS in post-stroke chronic aphasia. Author(s) Disclosures The authors have nothing to declare.