A study published in Cerebral Cortex, demonstrates that when one brain area loses functionality, a “back-up” group of secondary brain areas immediately activate, replacing not only the unavailable area but also its collateral areas.
Scientists at Carnegie Mellon University’s Center for Cognitive Brain Imaging (CCBI) have used a combination of neural imaging methods to discover how the human brain adapts to injury. Functional magnetic resonance imaging (fMRI) was used to study precisely how the brains of 16 healthy adults adapted to the temporary incapacitation of the Wernicke area, the brain’s key region involved in language comprehension. They applied Transcranial Magnetic Stimulation (TMS) in the middle of the fMRI scan to temporarily disable the Wernicke area in the participants’ brains. During this time, the participants were asked to perform a sentence comprehension task before, during and after the TMS was applied.
The fMRI scans measured how the brain activity changed immediately following stimulation to the Wernicke area. The results demonstrated that as the brain function in the Wernicke area decreased following the application of TMS, a group of secondary brain areas immediately became activated and coordinated, allowing the individual’s thought process to continue with no decrease in comprehension performance. Three brain regions compensated for the virtually disabled region: 1) the contralateral areas — areas that are in the mirror-image location of the brain; 2) areas that are next to the impaired; and 3) a frontal executive area. It is interesting to note that the first two areas are functionally similar to the virtually impaired Wernicke area and the third area coordinates the response to the impairment.
The authors point out that following the TMS, the impaired area and its partners gradually returned to their previous levels of coordinated activity, while the newly activated brain areas were still in place. This approach reveals some principles of network-level adaptation to trauma with potential application to traumatic brain injury, stroke, and seizure.