Association between therapy outcome and right-hemispheric activation in chronic aphasia

TLDR

The role of the right hemisphere in language processing and therapy success for aphasic patients is debated. The study examined how right‑hemispheric and left‑perilesional activation during language tasks relates to outcomes of constraint‑induced aphasia therapy. fMRI was used to measure activation during word‑reading and word‑stem completion in 16 chronic non‑fluent aphasic patients and 8 healthy controls before and after therapy. Higher pre‑therapy activation in right‑hemispheric regions, especially IFG/insula, predicted better therapy outcomes, while therapy itself did not alter activation patterns.

Abstract

The role of the right hemisphere for language processing and successful therapeutic interventions in aphasic patients is a matter of debate. This study explored brain activation in right-hemispheric areas and left-hemispheric perilesional areas in response to language tasks in chronic non-fluent aphasic patients before and after constraint-induced aphasia therapy (CIAT). In particular, we analysed the relation between brain responses and therapy outcome. Using functional magnetic resonance imaging (fMRI), brain activation was measured during word-reading (REA) and word-stem completion (COM) in 16 chronic non-fluent aphasic and 8 healthy subjects. Before therapy, activation in right inferior frontal gyrus/insula (IFG/IC) was stronger in aphasics compared to controls during REA and in precentral gyrus (PCG) during COM. Therapeutic intervention per se did not change brain activation for either task across all aphasic subjects. However, therapeutic success correlated with a relative decrease of activation in right-hemispheric areas, including the IFG/IC. Most importantly, initial activation in right IFG/IC and other right-hemispheric areas correlated positively with subsequent therapy success. Thus, right-hemispheric activation prior to aphasia therapy strongly predicts therapeutic success, suggesting that brain activation in chronic aphasia indicates the patients' potential for further language improvement.