Brain’s organization switches as children become adults

A child confronting an outraged parent demanding to know “What were you thinking?” now has a new response: “Scientists have discovered that my brain is organized differently than yours.”

But the same new study also provides parents with a rejoinder: While the overarching organization scheme differs, one of the most important core principals of adult brain organization is present in the brains of children as young as 7.

“Regardless of how tempting it might be to assume otherwise, a normal child’s brain is not inherently disorganized or chaotic,” said senior author Steven E. Petersen, Ph.D., the James McDonnell Professor of Cognitive Neuroscience. “It’s differently organized but at least as capable as an adult brain.”

The findings are published online in Public Library of Science Computational Biology by School of Medicine and Oregon Health and Science University researchers.

Petersen and his colleagues study normal brain organization and development to learn more about how developmental disorders and brain injury can impair mental capabilities. They plan to apply what they learn to develop new treatments for such disorders.

The researchers use resting-state functional connectivity MRI to identify and study brain networks. Resting-state connectivity scans the spontaneous activity that takes place in volunteers’ brains when they 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.

Through such studies, scientists previously revealed four brain networks with varying responsibilities in the adult brain. The networks typically involve tight links between several brain regions that are physically distant from each other. However, the new study showed that most of the tightest connections in a child’s brain are between regions that are physically close to each other.

Damien A. Fair, Ph.D., a former WUSTL graduate student now at Oregon Health and Science University, and Alexander L. Cohen, a WUSTL graduate student, led the study and directed analysis of data from 210 subjects ranging from 7 to 31 years old.

“We took a group of the youngest subjects, analyzed their results, then dropped data from the youngest and added data from the next-oldest and redid the analysis until we had worked our way through all subjects,” Fair said. “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.”

Researchers also checked children’s brains for “small-world” organization, also present in adult brains. This is sometimes called “Kevin Bacon” organization after the trivia game known as “Six Degrees of Kevin Bacon.” The game highlights the ease of connecting any actor or actress to Kevin Bacon in six movies or less through links among various co-stars.

“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 said. “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 knew that children had fewer long-distance links among brain regions than adults, but when they looked more closely, they found there were enough of these links and nodes with multiple connections to establish small-world organization.