Researchers have used a new combination of neural imaging methods for the first time to show how the brain adapts after an injury.
Scientists at Carnegie Mellon University’s Center for Cognitive Brain Imaging showed that when one part of the brain is injured, a “backup” team of secondary brain areas activates immediately. These secondary areas replace both the unavailable area and its confederates.
“The human brain has a remarkable ability to adapt to various types of trauma, such as traumatic brain injury and stroke, making it possible for people to continue functioning after key brain areas have been damaged,” said Marcel Just, the D. O. Hebb Professor of Psychology at CMU and CCBI director. “It is now clear how the brain can naturally rebound from injuries and gives us indications of how individuals can train their brains to be prepared for easier recovery. The secret is to develop alternative thinking styles, the way a switch-hitter develops alternative batting styles. Then, if a muscle in one arm is injured, they can use the batting style that relies more on the uninjured arm.”
For the study, Just, Robert Mason, senior research psychologist at CMU, and Chantel Prat, assistant professor of psychology at the University of Washington, used functional magnetic resonance imaging (fMRI) in their study. The researchers studied the brains of 16 healthy adults whose brains were temporarily disabled in the Wernicke area by the use of Transcranial Magnetic Stimulation (TMS) in the middle of a MRI scan. The Wernicke area plays a major role in sentence comprehension.
The participants did a sentence comprehension task before, during and after the application of TMS. The MRI scans were used to measure how the brain activity decreased after the TMS. Researchers found that a backup team of secondary brain areas immediately activated and became coordinated. The participants were able to continue their thought processes with no decrease in comprehension performance.
There are three types of brain regions that act as backups:
- contralateral areas —areas in the mirror-image location of the brain
- reas that are right next to the impaired area
- a frontal executive area
“The first two types of back-up areas have similar brain capabilities as the impaired Wernicke area, although they are less efficient at the capability,” Just said. “The third area plays a strategic role as in responding to the initial impairment and recruiting back-up areas with similar capabilities.”
The research showed that the impairment of the Wernicke area has a negative effect on its cortical partners. “Thinking is a network function,” Just explained. “When a key node of a network is impaired, the network that is closely collaborating with the impaired node is also impaired. People do their thinking with groups of brain areas, not with single brain areas.”
Mason observed that after the TMS, the impaired area of the brain and its partners gradually returned to their previous levels of coordinated activity, while the back-up team of brain areas remained in place. “This means, that for some period of time, there were two cortical teams operating simultaneously, explaining why performance is sometimes improved by TMS,” he said.
The research was published in February, 2013 in “Cerebral Cortex.”
