Right hemispheric structural plasticity across intensive language action therapy in chronic post-stroke aphasia

Background Aphasia is a debilitating language disorder usually caused by left-hemispheric brain damage that often persists into the chronic stage (>6 months poststroke). Intensive Language Action Therapy (ILAT) has been shown to enhance language recovery in chronic aphasia by promoting functional reorganization through action-embedded language use. However, less is known about treatment-induced structural neuroplasticity across ILAT. This study examined whether ILAT is accompanied by right-hemispheric grey matter volume (GMV) increases and their association with language improvement in chronic aphasia. Methods Voxel-based morphometry (VBM) was applied to structural magnetic resonance imaging (MRI) data from 14 individuals receiving ILAT for 2-4 weeks, using pre- and post-treatment MRI scans and Aachen Aphasia Test (AAT) scores to assess right-hemispheric increases in GMV and language performance improvements, respectively. Whole-brain analyses were complemented by predefined region-of-interest (ROI) analyses in perisylvian regions. Results VBM analysis across ILAT revealed a significant GMV increase in a cluster spanning the right insula and putamen. While these changes did not significantly correlate with language improvement, GMV at both pre- and post-intervention timepoints was associated with language performance at each corresponding timepoint. Pre-specified region-of-interest (ROI) analyses revealed that GMV increases across ILAT in the right superior temporal gyrus (STG) were significantly associated with language improvement across therapy. Conclusion Together, these findings suggest that short-term, intensive aphasia therapy is accompanied by regionally specific structural change. The insula/putamen may reflect residual structural capacity relevant to language function generally, while STG change tracked the degree of improvement more specifically. These findings, from a small sample, identify candidate regions for hypothesis-driven testing in larger, controlled cohorts.