Wednesday, January 25, 2006

Inside the Premature Brain

Part 3 of our magazine story on advanced MRI looks at efforts by Columbia University researchers to map brain abnormalities in preterm newborns.

By Paul Raeburn

This article was a feature story in Technology Review's December 2005/January 2006 print issue. It has been divided into three parts for presentation online. This is part 3; part 1 appeared on Monday, January 23, and part 2 on Tuesday, January 24.

Parts 1 and 2 discussed the work of John Port, a neuroradiologist at the Mayo Clinic who is using MRI to explore the parts of the brain that may be involved in bipolar disorder.

Diagnosing Development

The techniques Port is studying, if they prove successful, will be used in diagnosing people already showing signs of mental illness. But what about others who are predisposed to problems but have not yet begun to exhibit symptoms? Can the MRI technology help to find these people so that they can be helped before symptoms appear?

At Columbia, Peterson is trying to answer that question. He and collaborators are among the first to scan the brains of premature infants -- sometimes within days of their birth. The aim is to catalogue the types of brain abnormalities they discover and to devise ways to intervene earlier than ever before to try to correct or compensate for them.

Peterson first became interested in the complications of premature birth about 10 years ago, when he was beginning his psychiatric research at Yale University. He had discovered something very unusual in the brains of people with Tourette's syndrome. Most of us have asymmetries in our brains -- the left side doesn't exactly match the right. Most of us also have one eye that's bigger than the other (as portrait photographers will point out) and other minor asymmetries.

But the brains of people with Tourette's syndrome were different. "In the Tourette's brain, there seemed to be an absence of asymmetry," Peterson says. A similar absence of asymmetry had been observed in animals that survived complicated births. Peterson decided to look at children who had been born prematurely. Like Port, he is using the newest MRI technologies to try to obtain information that hasn't been available before.

There was a reason for his interest. Children born prematurely are at greater risk for learning disabilities and even psychiatric illnesses. Understanding how their brains are different should lead to new ways to help them.

As it happened, Laura Rowe Ment, a pediatric neurologist at Yale, was following a group of 500 premature children born between 1989 and 1992 as part of an ongoing study. Peterson and Ment set up a collaboration. "There were imaging reports suggesting various kinds of problems in the brain -- in terms of brain development. But they were uncontrolled, the numbers were small -- they were impressionistic," says Peterson.

Even given their smaller body size, premature kids tend to have disproportionately small heads. "The guess was that brain size would be reduced" later in life, says Peterson. Researchers also speculated that there would be damage to the white matter. Ment's kids, who were then about eight years old, were especially useful because she and her colleagues had documented everything that had happened to them since they were born.

The first thing Peterson did was use the MRI scanner to determine the size of the eight-year-old children's brains. The guess was right -- their brains were smaller than normal. But the decrease in size occurred only in certain brain regions -- the parts of the cortex that govern movement, vision, language, memory, and visual and spatial reasoning. "These regions were dramatically smaller," Peterson says. The other parts of their brains were normal size, or close to it.

The second guess -- about damage to white matter -- also proved accurate. There was less white matter in the motor regions of the children's brains, meaning there were relatively few wiring connections there. And the reduction in volume correlated with IQ scores. "The bigger the abnormality -- the more abnormal it was in all these regions -- the lower their IQ was," Peterson says.