It's hard to say what's going on in the heads of children, but a new study shows how it's going on.
Kids' brains are organized differently than those of adults, scientists have learned through a series of brain scans. The workings of children's neural connections are more governed by proximity to one another than is the case in adult brains, said Steven E. Petersen of the Washington University School of Medicine in St. Louis.
Petersen and his colleagues are interested in normal brain organization and development to learn more about how developmental disorders and brain injury can impair mental capabilities.
Their new findings on children's brains could be used to develop new treatments for such disorders.
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{{ video="LS_090515_brain-changes" title="How the Brain Changes as We Grow Up" caption="Brains scans of volunteers age 7 to 31 shows how organizational structures in the human brain undergo a major shift." }}
Brain networks
The researchers use resting-state functional connectivity MRI to identify and study brain networks. These scans show the spontaneous activity that takes place in brains while study subjects do nothing.
When this brain activity rises and falls at the same time in different brain regions, researchers conclude that those areas likely work together.
For the new study, Petersen and his colleagues scanned the brains of 210 subjects ranging from 7 to 31 years old. Researchers set the lower limit for study subjects at 7 years of age because the brain is approximately 95 percent of its adult size at this age.
Previous research revealed four brain networks with varying responsibilities in the adult brain that typically involve tight links between several brain regions that are physically distant from each other.
The new research found that this is not the case in children: Instead of having networks made of brain regions that are distant from each other but functionally linked, most of the tightest connections in a child's brain are between brain regions that are physically close to each other.
That doesn't mean that kids are more scatter-brained than adults though.
"Regardless of how tempting it might be to assume otherwise, a normal child's brain is not inherently disorganized or chaotic," Petersen said. "It's differently organized but at least as capable as an adult brain."
The scans also showed how the organization of the brain changes as we age.
"The result was a detailed movie of how the organizational transition from a child's brain to an adult's brain takes place. It clearly shows a switch from localized networks based on physical proximity to long-distance networks centered on functionality," said study team member Damien Fair, a graduate student at Washington University during the research, and now at Oregon Health and Science University.
As a person ages, those long-range networks become more efficient and then brain can use more of them, said study co-author Alex Cohen, a graduate student at Washington University.
"They're trying to solve the task of being a brain in a human body," he said. Kevin Bacon on the brain
Researchers also checked children's brains for "small-world" organization, another organizational quality present in adult brains. This is the same idea as the game "six degrees of Kevin Bacon," which connects any actor or actress to Kevin Bacon in six movies or less through their co-stars.
In this case, the "co-stars" are nodes in the brain.
"It's the idea of a large network that lets you connect one node with another in a relatively short number of steps via special nodes," Fair says. "Like Kevin Bacon, these special nodes have many connections to other nodes, allowing them to help shorten the amount of steps that have to be taken when connecting nodes."
Scientists already had some idea that children had many fewer long-distance links among brain regions than adults, but didn't know whether those connections could be seen in the function of the brain. When they looked more closely they found there were enough of these links and nodes with multiple connections to establish small-world organization.
The researchers are now examining ways to adapt the study, detailed online in the journal PLoS Computational Biology, to the changing physical geography of younger brains.
The research was supported by funding from the National Institutes of Health, National Science Foundation, John Merck Scholars Fund, Burroughs-Wellcome Fund, Dana Foundation, Ogle Family Fund, Washington University Chancellor's Graduate Fellowship and UNCF/Merck Graduate and Postgraduate and Science Research Fellowship.
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