Bilateral neural correlates of treatment-induced changes in chronic aphasia

Aphasia is a language disorder that results from brain damage. Aphasia negatively affects communicative skills and leads to severe disability. Therefore, a reliable prognosis for aphasia recovery is essential. One of the main prognostic factors for aphasia is lesion localization. Several studies investigated the role of damaged or spared brain structures in post-stroke recovery. Nevertheless, only a few of them considered the anatomical properties of both hemispheres. Furthermore, despite the impact of communication disorder on patients’ lives, there is no evidence f how lesion characteristics influence communicative abilities and their recovery in aphasia. Therefore, we aimed to find the bilateral neural correlates for therapy-induced changes in spontaneous speech and communicative abilities in chronic aphasia. For this purpose, we applied the state-of-the-art neuroimaging technique that allows studying structures in the white matter of the brain. The results suggest that improvement at the group level is observed only in spontaneous speech but not in communicative abilities nor aphasia severity. Another important highlight is that performance in untreated chronic aphasia and post-treatment improvements do not rely on the same structures in the same way, and left and right white matter structures often act as antagonists. Spontaneous speech and communicative abilities in chronic aphasia depend on the intactness of the left hemisphere structures, while better post-treatment improvement in these variables is observed in speakers with more anatomically profound homologue structures in the right hemisphere.