By Sophia Cariati

Jordan Giedd, a healthy 5-year-old boy from Silver Spring, MD, climbs onto a long, narrow table that fits snugly into the tubelike core of a magnetic resonance imaging (MRI) machine -- a device used to examine the inner workings of the body. His father, Jay Giedd, M.D., chief of brain imaging at the Child Psychiatry Branch of the National Institute of Mental Health (NIMH), and a technician, Michelle Williams, tuck pillows behind his neck and slip a plastic ring around his head. After reminding him to lie still, they slide the table into the tunnel so Jordan's upper body is inside the core while his feet are visible outside it. For about 30 minutes, he remains still as the machine makes rhythmic, loud noises and captures three-dimensional photos of his brain.

Over the course of five years, children like Jordan, who have normally developing brains, and those with neurodevelopmental disorders such as attention deficit hyperactivity disorder (ADHD), schizophrenia, and bipolar disorder, visit NIMH in Bethesda, MD, to take part in brain-imaging studies. These and hundreds of similar studies will create the first atlas of the healthy, growing mind and help researchers discover the basis for abnormalities.

"There is a big push for science to unlock the causes of neurodevelopmental disorders so that we can prevent and treat them," says David Amaral, Ph.D., professor of psychiatry and neuroscience at the University of California, Davis. "And MRI tests play an important role in this process."

The MRI Experience
On a recent visit to NIMH, I watched as eight children ages 4 and older arrived at the hospital with their parents. NIMH is one of seven centers across the U.S. compiling a database of normal brain development by repeatedly scanning the brains of 400 healthy children ages 3 to 18. In tandem, NIMH researchers use MRI to peer into the brains of hundreds of children with ADHD, bipolar disorder (manic-depressive illness), and childhood-onset schizophrenia. Most children will receive four MRIs during the course of their involvement -- children ages 3 to 6 will come back every few months, while older children, whose brains change less rapidly, return less frequently. Each child is a paid volunteer, recruited through local newspapers and community centers. The youngest children often come in pajamas, close to their bedtime, with their teddy bears in tow.

Williams and Maureen Tobin, a research assistant, help the children relax by telling them what to expect: "It doesn't hurt, and there aren't any needles. But the machine is kind of loud," they explain. Unlike other imaging techniques, MRI is noninvasive and doesn't involve radiation, so parents generally feel comfortable allowing their children to participate. To help the kids relax or, better yet, fall asleep, Mom or Dad sometimes reads a favorite bedtime story. Once inside the machine, children can see into the room through a mirror. Naturally, some of them are frightened by the noise or feel claustrophobic, even though their heads are outside of the machine. Though many are at first apprehensive about lying in such a small, loud space, Tobin estimates that less than 10% of all the children she sees are too frightened to actually participate.

Unraveling the Mysteries of the Brain
Equipped with what are basically multimillion-dollar oversized magnets, doctors can now use MRI to measure how the brain changes as a child matures and learns. Doctors can also see how brains respond when they perform specific tasks like counting to 10. Until recently it was accepted that most of brain maturation occurred in the first 18 months of life and that the process was complete by age 3, but MRI studies are revolutionizing the way we think about normal brain development. Experts now know that it continues throughout childhood and well into early adolescence.

Starting in 1987, Arthur Toga, Ph.D., professor of neurology and director of the Laboratory of Neuro Imaging at the University of California in Los Angeles, and his colleagues repeatedly analyzed the brain scans of healthy children ages 3 to 15 for up to four years. With the help of computers, they tracked changes. In children ages 3 to 6, the area of the brain that helps learn new behaviors and organize new skills underwent the most rapid growth. "This shows how important it is to stimulate children at these ages -- to play new games with them and to strategize," says Dr. Toga.

Insights into Autism
Autism, which is believed to affect up to 1 in 500 children, impairs normal communication skills and social inclinations. While most children can instinctively read other people's minds through facial expressions and body language, many with autism are unable to use these social cues.

MRI studies implicate the amygdala -- a part of the brain that controls social and emotional behavior -- in autism. Recently scientists at the University of Cambridge in England studied the brains of people with a mild form of autism and those of healthy individuals while both groups attempted to interpret facial expressions. The brain scans showed that the amygdala was "turned on" in the brains of healthy individuals during these exercises, while in the autistic brains it remained dormant.

Researchers from the University of Washington School of Medicine in Seattle found that this "social" area of the brain was smaller in people with autism. "Studies have found that there is something functionally and structurally irregular in the amygdala," says researcher Elizabeth Aylward, Ph.D.

Understanding ADHD
Although nearly one in every five children has a neurodevelopmental disorder, scientists are still unsure about what causes them and lack conclusive tests for their diagnosis. But for a condition such as ADHD, which affects 3% to 5% of children in this country, they're uncovering helpful information.

For years experts have debated whether ADHD is a real problem or a label too readily placed on rambunctious, healthy children. Unlike diabetes, a disease detected with a simple blood test, ADHD is diagnosed by observing a child's behavior. Parents, educators, and even some doctors argue that this "fuzzy" technique has led to an overdiagnosis of ADHD, resulting in the overmedication of many children. But brain-imaging studies are finally providing proof that ADHD has a biological origin.

In 1996, F. Xavier Castellanos, M.D., chief of the ADHD Research Unit at the child psychiatry branch of NIMH, led a landmark MRI study that compared the brains of boys diagnosed with ADHD to the brains of those without. "The first step was to find out if the brains are different," said Dr. Giedd, coauthor of the study, "and we've established that pretty solidly now." Overall, brain size is about 5% smaller in children with ADHD, mainly because of the smaller size of two areas involved in attention, the frontal cortex and the basal ganglia. Other studies have since shown that the basal ganglia of kids with ADHD are less active during attention tests, and that Ritalin, a stimulant, increases activity in this part of the brain.

Still, MRI can't yet be used to diagnose this or similar psychiatric conditions. On the whole, brain scans of children with ADHD, autism, and other conditions are different from those of children without ADHD, but the discrepancies are too small and too varied to be used for individual diagnoses. "The truth is, it is a very subtle finding," says Dr. Castellanos. "I can't just look at an MRI and say whether a child has ADHD."

If this combination of attention tests and MRI proves effective, it may lead to a definitive diagnosis, which would help everyone involved: "When you are committing a child to long-term medication, it's crucial to verify the source of the illness or behavior," says Martin H. Teicher, M.D., Ph.D., professor of psychiatry at Harvard Medical School in Boston. "An MRI, along with the behavioral test, gives parents a much greater sense of confidence about using drugs."

Is MRI Right for Your Child?
As promising as brain scanning is, doctors caution that the field is still in its infancy. "It'll probably be five to 10 years before we can use MRI to diagnose," says Dr. Giedd. So spending the $800 to $2,000 it costs for a brain scan will probably make no difference to a child's diagnosis or treatment, says Judith L. Rapoport, M.D., chief of the child psychiatry branch at NIMH."But by using MRI as a research tool, we lay the groundwork for understanding what goes wrong in brain development and how it causes diseases," Dr. Rapoport says.

What's more, insurance companies will not compensate for MRIs performed on patients with neuropsychiatric conditions. If brain imaging can identify these disorders, they'll have an impetus to cover MRIs. Earlier diagnosis will allow for earlier intervention and better prognoses -- "money in the bank for insurers," explains Dr. Teicher.

For now, diagnostic and treatment options for children with neurodevelopmental disorders are limited. "But if we can understand what affects brain development, then we can get to the next step of intervention and give practical advice to parents, teachers, and children," says Dr. Giedd.