CARNEGIE MELLON (US) — When injury causes one area of the brain to lose function, secondary brain areas activate to fill in the gap.
“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,” says Marcel Just, professor of psychology at Carnegie Mellon University and director of its Center for Cognitive Brain Imaging.
“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, published in the journal Cerebral Cortex, Just, senior research psychologist Robert Mason, and Chantel Prat, assistant professor of psychology at the University of Washington, used functional magnetic resonance imaging (fMRI) 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. While in the MRI scanner, participants were performing a sentence comprehension task before, during, and after the TMS was applied. Normally, this area of the brain is a major player in sentence comprehension.
The fMRI scans were used to measure how the brain activity changed immediately following stimulation. The results showed that as the brain function in the Wernicke area decreased following the application of TMS, a “back-up” team of secondary brain areas immediately became activated and coordinated, allowing the individual’s thought process to continue with no decrease in comprehension performance.
The brain’s back-up team consisted of three types of brain regions: contralateral areas that are in the mirror-image location of the brain; areas that are right next to the impaired area; and 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 says. “The third area plays a strategic role as in responding to the initial impairment and recruiting back-up areas with similar capabilities.”
Additionally, the research showed that impairing this area of the brain also negatively affected the cortical partners with which it had been working. “Thinking is a network function,” Just explains. “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.”
Following the TMS, the impaired area and its partners gradually returned to their previous levels of coordinated activity, while the back-up team of brain areas was still in place, Mason says.
“This means, that for some period of time, there were two cortical teams operating simultaneously, explaining why performance is sometimes improved by TMS.”
Source: Carnegie Mellon University