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Convergent Resting State fMRI and EEG Evidence of Speech-Language Therapy and tDCS Impacts on Brain Network Connectivity for an Individual with Stroke Aphasia

Poster B88 in Poster Session B, Tuesday, October 24, 3:30 - 5:15 pm CEST, Espace Vieux-Port

Evan Houldin1,2, Sameer Ashaie1,2, Julio Pavon1,2, Leora Cherney1,2; 1Shirley Ryan AbilityLab, 2Northwestern University

INTRODUCTION: Recent studies suggest that transcranial direct current stimulation (tDCS) combined with speech-language therapy (SLT) may enhance treatment outcomes in individuals with aphasia. However, recent reviews also highlight the inconsistent impact of tDCS on treatment outcomes in individuals with aphasia. This variability in results could be explained by our lack of understanding of how tDCS combined with SLT modulates residual brain networks to impact behavioral performance. The aim of the present study was to investigate changes in conversational performance and brain network functional connectivity (FC), following intensive tDCS and SLT. Multiple imaging modalities (i.e., fMRI, EEG) were used to provide converging evidence. METHOD: The participant, P1 (right-handed male, aged 49.84) was 71.74 months post-stroke onset. P1’s WAB-R Aphasia Quotient was 65.8. P1 received 40 minutes of SLT, in the form of computer-based script practice. tDCS (2mA) was concurrently administered with the SLT for the first 20 minutes. MRI-guided neuronavigation was used to place the ‘target’ cathodal tDCS electrode above right angular gyrus (rAG) and the ‘return’ anodal electrode above center supraorbital area. P1 received 15 sessions of tDCS/SLT over 3 weeks. Resting-state fMRI data was collected pre- and post-intervention. Seed-based correlation was used to assess connectivity with AG-associated regions; e.g., default mode network (DMN). Graph analysis was used to evaluate changes in brain network properties such as intra-hemispheric FC (IHC). These properties were compared to 18 age/sex-matched healthy controls. Resting-state (rs)EEG responses were also recorded with eyes open for 3 minutes with a 64-channel system before and after treatment, on days 1, 5, 10, and 15. EEG data was analyzed in source space, with signals extracted from 4 regions of interest (left/right inferior frontal gyrus (l/rIFG), l/rAG). In order to assess changes in left- and right-hemisphere FC, a coherence analysis was performed between lIFG/lAG signals and between rIFG/rAG signals, respectively. RESULTS: The primary behavioral measure was the pre- to post-treatment change in accuracy of script-related words during the simulated conversation. Performance improved from baseline to immediately post-treatment (106.4% increase). 8/9 resting-state fMRI graph measures were found to change towards those of controls after treatment. In particular, left IHC (evaluated as the proportion of 95th-percentile to total-number-of intra-hemispheric FC edges), increased from .030 to .041, vs. the .053 healthy control mean (95% CI: .051-.056). Concurrently, right IHC decreased from .101 to .088, vs. the .066 healthy control mean (95% CI: .062-.070). Within-DMN FC also increased post-intervention. Our EEG analysis also indicated left-hemisphere FC increases post-treatment, and right-hemisphere FC decreases post-treatment. CONCLUSION: Our results suggest that cathodal tDCS applied to rAG combined with SLT increases left-hemisphere FC while decreasing right-hemisphere FC. Further, FC patterns approaching those of healthy controls may result in improvement in behavioral performance in individuals with aphasia. Results are also in line with previous brain stimulation studies indicating that left-hemisphere connectivity increases improve speech/language task performance. rsEEG results indicate ongoing impact of treatment sessions on residual brain FC. Future research is needed to further understand the differential impact of tDCS and SLT on functional network connectivity and behavioral performance.

Topic Areas: Speech-Language Treatment,

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