Right hemisphere brain damage impairs strategy updating
Recovery rates vary greatly, for reasons that are poorly understood .The relationships between lesion site, activity pattern changes, and recovered language functions remain unclear.For example, particularly severe participants may have larger lesions or lesions in highly critical areas.If this is the case, then the relationship between left hemisphere activity and language performance may be indirect, in that both are actually dependent on the severity and size of the stroke itself, as well as the availability of left hemisphere tissue adjacent to the critical areas.In neuroimaging studies, patterns of increased activation during language tasks in chronic aphasia have been broadly consistent across studies.In a meta-analysis of neuroimaging studies, collapsing across a wide range of language tasks, we found that people with aphasia consistently overactivated perilesional regions in the left hemisphere, as well as right hemisphere regions that were homotopic to the left hemisphere language network .
However, the relationship between lesion size, location, and ability to use these preserved regions has not been carefully examined.
The great virtue of specific biological hypotheses is that they generate specific testable predictions, especially with regard to the timing of plasticity, the relationship of specific lesion features such as size and location to the pattern of reorganization, and the relationship of brain changes to behavioral outcomes.
One such biological hypothesis which has gained a great deal of traction in recent years is the interhemispheric inhibition model, which is commonly invoked to explain recruitment of homotopic right hemisphere processors, negative relationships between right hemisphere activity and language performance, and the beneficial effects of right PTr inhibition .
Unfortunately, the same concerns arise when examining the function of the right hemisphere as were raised for the left, specifically, confounding with lesion size and location.
The usefulness of a shift from right to left hemisphere activation during the chronic stages likely depends on the availability of remaining healthy left hemisphere tissue .
In particular, people with lesions in the left inferior frontal gyrus (IFG) were more likely to recruit right IFG than those without lesions in that area.