September 20, 2010

Charting Brain Maturity

Schematic of a brain showing colorful connections within Scientists used a new technique to visualize functional connections within the brain as it matures. Orange rods indicate connections that strengthen with age, and green represents links that weaken with age. Dosenbach et al., Science.

Researchers used advanced imaging to chart individuals' brain maturity based on the functional connections between brain regions. The finding raises the possibility that brain scanning data may one day be used to monitor psychiatric and developmental disorders.

Researchers hope to use functional magnetic resonance imaging (fMRI) to help diagnose developmental delays and neuropsychiatric disorders that don't have obvious structural brain abnormalities. Previous developmental fMRI studies have been able to distinguish between brain development in children and adults. A group led by Drs. Nico Dosenbach and Bradley Schlaggar at the Washington University School of Medicine in St. Louis set out to see if they could go a step further and develop a way to predict brain maturation in individuals.

The researchers used a variation of fMRI called resting state functional connectivity MRI (fcMRI). This technique measures blood oxygen levels to detect correlations in activity between different brain regions. Regions with highly correlated patterns of activity while a person is at rest have strong functional connectivity. With fcMRI, data can be collected quickly and easily under different resting conditions, including anesthesia, sleep and quiet rest. Past studies have shown fcMRI measurements to be reliable across scans and different institutions. The researchers collected data on blood oxygen levels in 5-minute scans of 238 participants ranging in age from 7 to 30 years old.

To analyze the data, the scientists used multivariate pattern analysis techniques, which allow for continuous predictions about the relative functional maturity levels of individual brains. The study was funded by NIH’s National Institute of Neurological Disorders and Stroke (NINDS) and National Institute of Mental Health (NIMH), along with other sources.

The analysis, reported in the September 10, 2010, issue of Science, showed that changes in functional maturity levels between the ages of 7 and 30 years look much like the growth curves for height, head circumference and other measures used by pediatricians.

The scientists found that the region with the greatest relative prediction power about brain maturity was the right anterior prefrontal cortex. This region is thought to be important for cognitive control and higher-order reasoning. Interestingly, weakening connections between brain regions contributed more to predicting brain maturity than strengthening connections (68% versus 32%).

This approach could help researchers understand the causes of, and explore new treatments for, brain development disorders such as autism or attention-deficit disorder.

"Pediatricians regularly plot where their patients are in terms of height, weight and other measures, and then match these up to standardized curves that track typical developmental pathways," Schlaggar says. "When the patient deviates too strongly from the standardized ranges or veers suddenly from one developmental path to another, the physician knows there's a need to start asking why." Brain scanning data may one day provide similar guidance for monitoring and treating psychiatric and developmental disorders.

—by Harrison Wein, Ph.D.

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