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Nerve cell key to child disorder hild problem shows in scans

SCIENTISTS HAVE located the sites in the brain that appear to play a critical role in causing hyperactivity and attention deficit disorder, which affects an estimated 1 in 20 children.

Images from a type of brain scanner that can measure electrical activity have revealedchildren with attention deficit and hyperactivity disorder (ADHD) show marked differences to the healthy controls.

Doctors once considered hyperactivity as a temporary behavioural problem, but recent research points to an underlying biological condition that can extend into adulthood.

Chandan Vaidya, who led the research team from Stanford University in California, found that the nerve cells of ADHD children were more active than normal in the brain's frontal lobe cortex and less active in the striatal region just below, which is known to control movements.

The results support the growing belief that ADHD is the result of a physical imbalance in brain development which manifests in early childhood as an inability to concentrate, fidgeting and impulsiveness. "The long-term consequences include lower educationaloutcomes and in-creased risk ofdrug abuse in adulthood," the researchers report in Proceedings of the National Academy of Sciences.

The researchers used a functional magnetic resonance scanner to study 10 boys with ADHD and six normal boys. When they were given Ritalin, the stimulant drug used to control ADHD, the differences between the groups were dramatic. It reduced the striatal activity of the normal boys but increased it in ADHD children - showing how Ritalin affects the brain in situ. The researchers suggest that scanners be used to make a more accurate diagnosis.