LH lesions lead to increased RH FC, but the pattern of results suggests that these changes may not reflect meaningful functional reorganization that contributes to language function after stroke.
Chronic left hemisphere stroke survivors showed higher overall within-RH functional connectivity compared to healthy controls.
Few of the RH functional connectivity differences observed in stroke survivors were found within the RH language network specifically.
Greater RH functional connectivity was not associated with lesion location or reduced FC in homotopic left hemisphere regions.
Right hemisphere functional connectivity was not associated with behavioral language outcomes in chronic stroke survivors.
The magnitude of RH functional connectivity differences between stroke survivors and controls was proportional to left hemisphere lesion size.
The study used a naturalistic movie-watching fMRI paradigm alongside a validated semantic decision task to characterize functional connectivity and define language networks.
This research suggests that when people suffer a stroke on the left side of the brain — the side that typically controls language — the right side of the brain shows increased internal connectivity (i.e., its regions communicate more with each other). This increase in right hemisphere activity is larger when the stroke damage is more extensive. These findings come from a brain imaging study comparing 85 chronic stroke survivors to 71 healthy adults using a movie-watching brain scan and a language task to map language-related brain regions. However, the study found that these right hemisphere changes are not happening specifically in the language areas of the right brain, and they are not linked to how well stroke survivors can use language. Instead, the changes are spread widely across the right hemisphere and occur between different brain networks rather than within the right hemisphere's language network. Additionally, the increased right hemisphere connectivity was not related to which specific left hemisphere regions were damaged, except in a few limited cases involving temporal lobe damage. This research suggests that the commonly held idea that the right hemisphere 'takes over' language functions after a left hemisphere stroke may be an oversimplification. The broad, non-language-specific nature of right hemisphere connectivity changes, combined with the lack of any relationship to language recovery, indicates these changes may reflect a general brain response to injury rather than meaningful reorganization that helps people recover language abilities. This has implications for rehabilitation approaches that aim to boost right hemisphere involvement in language recovery.
Vladyko N, DeMarco A, Turkeltaub P. (2026). Right Hemisphere Functional Connectivity Increases in Proportion to Left Hemisphere Lesion Size, but Not Within the Language Network.. Human brain mapping. https://doi.org/10.1002/hbm.70631