The human brain has a region that specializes in facial recognition and grows in density over time, allowing adults to recognize faces considerably better than children do. This was the chief takeaway in a new study from Stanford University researchers released earlier in the week and published in the journal Science.
A report from NPR detailed these findings in brief, as researchers analyzed brain scans of close to 50 individuals – 25 adults and 22 children. Looking at the scans, the part of the brain designed to aid in facial recognition grows continuously even after a person is past adolescence. And while the region didn't gain more neurons, it did grow additional tissue, allowing it to better support neurons.
"You can imagine a 10-foot by 10-foot garden, and it has some number of flowers in there," said Jesse Gomez, a Stanford University graduate student and lead author of the study. "The number of flowers isn't changing, but their stems and branches and leaves are getting more complex."Speaking to Live Science, Gomez added that development patterns may vary depending on the person, with some adults, for instance, having poor facial recognition skills and "child-like" density in the region responsible for recognizing faces.
"There are some kids that have adult-like tissue values, but those kids also have adult-like brain function."The researchers used a technique called qualitative magnetic resonance imaging, or qMRI, which varies from standard MRI as it doesn't just differentiate between white matter and gray matter, but also provides information on brain cell density that could allow for person-to-person comparisons. Live Science noted that qMRI works by "exciting protons in the water in brain tissue," with researchers then measuring the time it takes for protons to return to a relaxed state and using that information to help measure brain density.
When comparing the adult brains to those of the children, the researchers discovered faster relaxation times in the adult group, but only spotted this in the facial recognition area. This trend wasn't visible in a nearby area of the brain that is responsible for helping people recognize places and locations.
In an effort to determine the type of brain tissue causing the facial recognition area to become denser over time, Gomez's team used computer modeling to test several theories. According to Live Science, it's been established that the brain gains myelin – an insulating substance that grows on the axons of neurons – over time. But the computer modeling tests showed that the idea of myelin alone causing the increase in density was just too simplistic.
After analyzing anatomical samples of deceased adult brains, the researchers then discovered that the facial recognition areas of these brains actually had fewer cell bodies than the place recognition areas.
"That tells us the tissue that is growing can't be the cell bodies, so it must be the 'neural fill,'" Gomez observed.
Stanford psychology professor and fellow researcher Kalanit Grill-Spector believes that the steady improvement in facial recognition and the related tissue growth in the brain region that allows this is the body's natural response to the need to recognize more and more faces as children grow into adolescence, then young adulthood.
"When you're a young child, you need to recognize your family and a handful of friends. But by the time you've reached high school or college your social group has expanded to hundreds or even thousands of people."Penn State University assistant professor of psychology Suzy Scherf, who was not involved in the study, told NPR that the changes may also help children in recognizing different facial types as they age. While a young child would primarily recognize faces of adults, such as their parents and other relatives, facial recognition in adolescents may be more predisposed toward recognizing adolescent faces.
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