Image showing bilateral cuneal (magenta) and frontal cortex (brown). Credit: eLife/University of Cambridge
As humans, when we need help with something, we recruit family and friends to overcome the burden. Apparently, our brains do something similar when they need help, too.
Scientists at the University of Cambridge have found the strongest evidence yet that our brains compensate for age-related deterioration by recruiting other areas to help with brain function and cognitive performance.
Previous brain imaging studies have confirmed that other parts of the brain get involved when the brain starts to gradually atrophy with age, However, until now, it was not clear whether the “recruitment” had an impact on cognitive performance.
It does, according to the new study published in eLife by scientists at the University of Cambridge in collaboration with the University of Sussex.
Humans’ ability to solve abstract problems is a sign of so-called “fluid intelligence.” Fluid intelligence tasks—like solving puzzles—engage the multiple demand network (MDN), a brain network involving regions both at the front and rear of the brain. However, its activity decreases with age.
To see whether the brain compensated for this decrease in performance, the British teams analyzed imaging data from 223 adults between 19 and 87 years of age.
The study volunteers completed “odd-one-out” puzzles of varying difficulty while lying in a functional magnetic resonance imaging (fMRI) scanner. The scanner allowed researchers to observe and record patterns of brain activity by measuring changes in blood flow in real-time.
As expected, the researchers found that the MDN was particularly active, as were regions of the brain involved in processing visual information. The team was also not surprised to find that, in general, the ability to solve problems decreased with age. However, when they looked further into the images using machine learning techniques, they did find something surprising.
In the brains of older people, two specific areas—the cuneus, at the rear of the brain, and a region in the frontal cortex—showed greater activity that correlated with better performance on the task. Moreover, activity in the cuneus region was related to performance of the task more strongly in older than younger volunteers, and contained extra information about the task beyond the MDN.
Although it is not clear exactly why the cuneus should be recruited for this task, the researchers point out that this brain region is usually good at helping humans stay focused on what we see. Older adults often have a harder time briefly remembering information that they have just seen, like the complex puzzle pieces used in the task. The increased activity in the cuneus might reflect a change in how often older adults look at these pieces, as a strategy to make up for poorer visual memory.
Ultimately, the results of this new study confirm that brain compensation in later life does not rely on the multiple demand network as previously assumed; rather, the brain recruits areas whose function is preserved in aging. This could help scientists tailor treatment and more accurately leverage areas of the brain that are not affected by neurodegenerative diseases.
“Now that we’ve seen this compensation happening, we can start to ask questions about why it happens for some older people, but not others, and in some tasks, but not others,” concluded study author Ethan Knights, lecturer at the Unviersity of Cambridge. “Is there something special about these people—their education or lifestyle, for example? And if so, is there a way we can intervene to help others see similar benefits?”