Plasticity of Language-Related Brain Function During Recovery From Stroke

Abstract

Background and Purpose-This study was undertaken to correlate functional recovery from aphasia after acute stroke with the temporal evolution of the anatomic, physiological, and functional changes as measured by MRI. Methods-Blood oxygenation level-dependent contrast and echo-planar MRI were used to map language comprehension in 6 normal adults and in 2 adult patients during recovery from acute stroke presenting with aphasia. Perfusion, diffusion, sodium, and conventional anatomic MRI were used to follow physiological and structural changes. Results-The normal activation pattern for language comprehension showed activation predominately in left-sided Wernicke's and Broca's areas, with laterality ratios of 0.8 and 0.3, respectively. Recovery of the patient confirmed as having a completed stroke affecting Broca's area occurred rapidly with a shift of activation to the homologous region in the right hemisphere within 3 days, with continued rightward lateralization over 6 months. In the second patient, in whom mapping was performed fortuitously before stroke, recovery of a Wernicke's aphasia showed a similar increasing rightward shift in activation recruitment over 9 months after the event. Conclusions-Recovery of aphasia in adults can occur rapidly and is concomitant with an activation pattern that changes from left to a homologous right hemispheric pattern. Such recovery occurs even when the stroke evolves to completion. Such plasticity must be considered when evaluating stroke interventions based on behavioral and neurological measurements. (Stroke. 1999;30:749-754.)

Neural deficits in children with dyslexia ameliorated by behavioral remediation: Evidence from functional MRI

“…A number of right hemisphere regions showed increases in activity after remediation, including right inferior and superior frontal gyri, and middle temporal gyrus. These results are consistent with studies of recovery of function after left hemisphere damage that have shown increased activity in right hemisphere homologues of left hemisphere language areas associated with improved language ability (16)(17)(18).…”

“…In addition to this ''normalizing'' effect of remediation, we hypothesized there would be changes in brain function in regions not normally active during phonological processing (compensatory effects), especially in right hemisphere homologues to left hemisphere language areas. Previous research on recovery of function after brain injury has shown that, in the face of left hemisphere damage, the right hemisphere can increase its activity in a compensatory manner (16)(17)(18). Because we suspected that the remediation may only partly ameliorate the left hemisphere disruptions, it was hypothesized that right hemisphere compenAbbreviations: fMRI, functional MRI; ROI, region of interest.…”

fMRI investigation of sentence comprehension by eye and by ear: Modality fingerprints on cognitive processes

“…Future fMRI studies of patients with brain damage may eventually reveal why a given patient has a particular type of comprehension deficit [cf. Thulborn et al, 1999].…”

Language Localization in Cases of Left Temporal Lobe Arachnoid Cyst: Evidence against Interhemispheric Reorganization

“…This may occur into ipsilateral cortex (Lazar et al, 1997;Rossini et al, 1998). When sufficient damage has occurred (Kertesz, Lau, & Polk, 1993), the contralateral hemisphere has also been shown to play a role in recovery from aphasia in adults (Thomas et al, 1997;Karbe et al, 1998;Thulborn et al, 1999). The hypothesis that arachnoid cysts lead to reorganization suggests that the location of language functions may be considerably different in this patient group than in a normal control group.…”