Yes, there are gender differences in cognitive function, but they're more limited than previously thought. And yes, income does affect cognitive performance -- but less than expected when only healthy children are considered. And while basic cognitive skills steadily improve in middle childhood, they then seem to level off -- questioning the idea of a burst of brain development in adolescence. These findings are the first data to emerge from the National Institutes of Health (NIH) MRI Study of Normal Brain Development, a large, population-based study that began in 1999 and is documenting structural brain development and behavior from birth to young adulthood.
The analysis, led by Deborah P. Waber, PhD in the Department of Psychiatry at Children's Hospital Boston, focused on cognition and behavior in healthy 6- to 18-year-olds enrolled at Children's and five other metropolitan areas across the United States. Population-based sampling techniques used U.S. Census data to ensure demographic diversity. A rigorous screening process eliminated children with medical, neurologic or psychiatric disorders, familial risk factors for such disorders, or prenatal exposure to toxic substances, providing a glimpse of how a healthy brain develops.
"This report -- and many others that will follow -- provides a comprehensive set of benchmark values that clinicians and scientists studying brain development can reference for many years to come," said NIH Director Elias A. Zerhouni, MD.
From an initial sample of more than 35,000 target families, the researchers were able to enroll approximately 450 children, of whom 385 were 6 years or older. Once enrolled, the children underwent MRI scans of the brain and completed a battery of behavioral and cognitive tests to ascertain their overall IQ, verbal ability, mental processing speed, spatial ability, memory, fine motor dexterity, psychosocial function, reading and calculation ability, and other measures of cognitive function. Most have returned two more times so that their development can be tracked.
Overall, this healthy group performed better than previously reported norms. However, analysis of the first wave of data also found that:
"In the past, studies of structural brain development and often studies of cognitive development were performed on samples of convenience that weren't necessarily representative of the overall population," Waber adds. "This study provides information on a much more diverse and representative sample, and a much larger one than previously available."Other components of the NIH MRI Study of Normal Brain Development are structural brain imaging with MRI, magnetic resonance spectroscopy (MRS), and diffusion tensor imaging (DTI) to study the growth of different brain structures and the formation of connections between them, and even changes in brain chemistry. The ultimate goals of the project are to provide an atlas of the development of the healthy child's brain and to link the imaging findings with neurobehavioral function.
Waber's co-authors were Carl de Moor and Peter Forbes, Department of Psychiatry, Children's Hospital Boston; C. Robert Almli and Kelly Botteron of Washington University School of Medicine, St. Louis; Gabriel Leonard and Denise Milovan of McGill University, Montreal; Tomas Paus of McGill University and the University of Nottingham (UK), and Judith Rumsey of the National Institute of Mental Health.
The six Pediatric Study Centers are Children's Hospital Boston; Children's Hospital Medical Center of Cincinnati; Children's Hospital of Philadelphia; University of California at Los Angeles; University of Texas, Houston; and Washington University, St. Louis.
The study was funded by the National Institute of Neurological Disorders and Stroke, the National Institute of Mental Health, the National Institute of Child Health and Human Development and the National Institute on Drug Abuse.
Article: "The NIH MRI study of normal brain development: performance of a population based sample of healthy children aged 6 to 18 years on a neuropsychological battery," May 18, Journal of the International Neuropsychological Society.
Materials provided by Children's Hospital Boston. Note: Content may be edited for style and length.
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