The complementary role of the cerebral hemispheres in recovery from aphasia after stroke: A critical review of literature

Objectives: To review the literature on the specific role of the right cerebral hemisphere during recovery from aphasia in order to address the lack of consensus among authors. To derive a theoretical model reconciling the controversial findings in the literature. Methods: Initial PubMed, MEDLINE (1946 to 5 May 2012) and PsycINFO (1806 to first week June 2012) searches on recovery mechanisms from aphasia, whether treatment-related or not, retrieved a total of 35 English language articles. Articles, cross-referenced in this initial set were also reviewed if they met the inclusion criteria, thus resulting in a total of 42 articles included in this review. Main outcomes: Recruitment of the right hemisphere during recovery from aphasia can be effective if it occurs during a critical time window post-stroke. The recruitment's effectiveness will depend on the lesion's location, extent and permanence. Preservation of core language processing areas will generate minimal right hemisphere recruitment and vice versa. Some experimental studies seem to suggest that the improvement linked to a particular hemisphere can be modulated by specific therapy methods. Conclusion: The specific conditions in which effective right recruitment takes place may have important implications for rehabilitation treatment. These findings could lead to improved recovery in people suffering from aphasia. However, more research with non-invasive brain stimulation is needed.