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Dynamics of language reorganization after stroke.
Dorothee Saur1, Rüdiger Lange, Annette Baumgaertner
1Department of Neurology, University Freiburg, Breisacher Strasse 64, 79106 Freiburg, Germany. dorothee.saur@uniklinik-freiburg.de
Brain : a Journal of Neurology
|April 28, 2006
Summary
Brain reorganization after stroke-induced aphasia involves three phases: initial low activation, followed by right-hemisphere language area recruitment correlating with recovery, and finally, normalization of left-hemisphere activation.
Area of Science:
- Neuroscience
- Neurology
- Cognitive Science
Background:
- Stroke-induced aphasia impacts language recovery.
- Previous studies suggest bilateral network involvement in chronic aphasia recovery.
- The dynamics of language system reorganization from acute to chronic stages remain unclear.
Purpose of the Study:
- To investigate the temporal dynamics of brain reorganization in the language system.
- To identify changes in brain activation patterns during aphasia recovery.
- To correlate brain activity changes with language function improvement.
Main Methods:
- Repeated functional MRI (fMRI) examinations in 14 acute stroke patients with aphasia.
- Auditory comprehension task using an event-related design.
- Parallel language testing from acute to chronic stages (1.8 to 321 days post-stroke).
Main Results:
- Acute phase: Reduced activation in left-hemispheric language areas.
- Subacute phase: Increased bilateral activation, particularly in the right Broca-homologue (BHo) and supplementary motor area (SMA), correlating with language improvement.
- Chronic phase: Normalization of activation with a shift back to left-hemispheric language areas.
Conclusions:
- Language recovery after stroke follows a three-phase reorganization process.
- Early recovery involves right-hemisphere recruitment, which is crucial for functional improvement.
- Later stages show a normalization of activation, suggesting consolidation of the language network.