The importance of the left hemisphere in language recovery in aphasia
Sims, Jordyn Ann
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Recovery from aphasia, loss of language following a cerebrovascular incident (stroke), is a complex process involving both left and right hemispheric regions. In our study, we analyzed the relationships between semantic processing behavioral data, lesion size and location, and functional signal change from functional magnetic resonance imaging (fMRI) data. Our study included 14 persons with aphasia in the chronic stage of recovery (six or more months post stroke) who performed semantic processing tasks of determining whether a written semantic feature matched a picture or whether two written words were related. Region of interest (ROI) analysis revealed that left inferior frontal gyrus pars opercularis and pars triangularis, despite significant damage, were the only regions to correlate with behavioral accuracy. Additionally, bilateral frontal regions including superior frontal gyrus, middle frontal gyrus, and anterior cingulate appear to serve as an assistive network in the case of damage to traditional language regions including inferior frontal gyrus, middle temporal gyrus, supramarginal gyrus, and angular gyrus. Contralesional posterior regions including right middle temporal gyrus, right supramarginal gyrus, and right angular gyrus are engaged in the case of complete damage to left hemisphere language regions. Additionally, right inferior frontal gyrus pars orbitalis is noted to be possibly serving a monitoring function. These results reinforce the importance of the left hemisphere in language processing in aphasia, as well as the nuanced relationships between lesion size, lesion location, and bilateral signal change in aphasia.
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