The question then was, Did these abnormalities arise at or before birth or sometime later? Peterson started scanning normal and premature infants. The scans of premature newborns showed that they had the same brain abnormalities as the eight-year-olds. "It was so distinctive, the pattern of abnormalities, it's almost impossible to look at a scan and not be able to tell this is a premature child," Peterson says.

One of the most salient differences was in the size of the tiny cavities in the brain known as ventricles. "The ventricles are massively dilated, about four times larger in the prematurely born kids than in the term children," Peterson says. "We saw that in eight-year-olds and in the infants. The tissue around those ventricles is really damaged....It suggests that these babies are having problems in development even before they're born." Peterson followed the newborns for two years and then tested them with a kind of IQ test meant for toddlers. The earlier they were born, the more immature their brains were at birth. And the more immature their brains, the lower their intelligence scores.

To neuroscientists, the discovery that premature kids had brain abnormalities made sense. Much of the brain's growth and development occurs during the last half of pregnancy. Neurons begin life clumped near the center of what will become the brain but soon start to migrate outward. Glial cells, which help neurons communicate, go through a period of explosive growth, accounting for most of the brain's increase in weight. The neurons extend meandering tentacles, seeking connections with other cells. Billions of connections are made during the last weeks of pregnancy. The axons then develop their coats of white, fatty insulation. By this time, the brain is massively overdeveloped, with far too many wires and connections. So it begins cutting back. It's as if each connection is tested, to determine its value. The useful circuits are kept; the others are trimmed away, leaving a sleek, efficient machine.

Premature birth likely disrupts these processes -- the migration of the nerve cells, the growth of glial cells and white matter, and the trimming. Premature kids have most of the neurons they will carry with them into adult life, but it's possible they're not in the right places or properly connected or tested. Researchers, says Peterson, are "intensively testing" these possibilities.

Peterson's research offers the hope of helping children compensate for whatever brain-related peculiarities they might have. "We want to use imaging to predict who's going to have particularly difficult problems in the course of development, so we can intervene more effectively," he says. That intervention might consist of specially designed education programs or physical therapy and other treatments to compensate for physical and emotional difficulties.

When Peterson began this work, his interest was professional. But now he has a personal interest as well. Two years ago, his daughter was born four weeks premature. While she shows no ill effects, he says he watches her, and he worries.