Cortical Language Activation in Stroke Patients Recovering From Aphasia With Functional MRI

TLDR

Two mechanisms for aphasia recovery—repair of damaged language networks and activation of compensatory areas—have been proposed. The study aimed to determine whether both mechanisms or only one occur in the brains of patients who have recovered from aphasia. Using blood‑oxygen‑level‑dependent fMRI, the authors examined cortical language networks during lexical‑semantic tasks in seven right‑handed patients at least five months post‑stroke who had regained substantial language function. Recovered aphasic patients exhibited increased right‑hemisphere language activity and decreased left‑hemisphere activity compared with controls, with bilateral networks associated with better recovery and right‑dominant networks arising when left‑hemisphere functions were not restored.

Abstract

Background and Purpose —Two mechanisms for recovery from aphasia, repair of damaged language networks and activation of compensatory areas, have been proposed. In this study, we investigated whether both mechanisms or one instead of the other take place in the brain of recovered aphasic patients . Methods —Using blood oxygenation level–dependent functional MRI (fMRI), we studied cortical language networks during lexical-semantic processing tasks in 7 right-handed aphasic patients at least 5 months after the onset of left-hemisphere stroke and had regained substantial language functions since then. Results —We found that in the recovered aphasic patient group, functional language activity significantly increased in the right hemisphere and nonsignificantly decreased in the left hemisphere compared with that in the normal group. Bilateral language networks resulted from partial restitution of damaged functions in the left hemisphere and activation of compensated (or recruited) areas in the right hemisphere. Failure to restore any language function in the left hemisphere led to predominantly right hemispheric networks in some individuals. However, better language recovery, at least for lexical-semantic processing, was observed in individuals who had bilateral rather than right hemisphere–predominant networks. Conclusions —The results indicate that the restoration of left-hemisphere language networks is associated with better recovery and inversely related to activity in the compensated or recruited areas of the right hemisphere.