Preserving Plasticity: New Directions in Research for the Developing Brain

Abstract

After completing this article, readers should be able to: 1. Characterize the process of corticogenesis. 2. Describe findings of magnetic resonance imaging of the developing brain. Cerebral development of the fetus is under genetic control, and during the third trimester of gestation, synapse development, dendritic spine elaboration, and cortical-cortical connections proceed as the period of developmental plasticity begins. In contrast to infants born at term, those who are born preterm can suffer significant developmental disability; many reports have shown that the neurodevelopmental outcome of very low-birthweight preterm infants is related directly to gestational age at birth. Infants weighing less than 1,000 g at birth now represent almost 1% of all live births in the United States, and the survival rate for this population approaches 85%. In stark contrast to the improved survival, however, are the emerging reports of neurodevelopmental disability in these very tiny and frequently critically ill infants. The incidence of cerebral palsy is increasing as the survival rate increases, and the incidence of cognitive deficits in this population has not changed during the past decade. The incidence of major neurodevelopmental handicaps in very preterm infants ranges from 12% to 32%, and even “healthy” preterm infants experience a high degree of educational difficulties. When we examined 200 very low-birthweight survivors of the Randomized Indomethacin Intraventricular Hemorrhage Prevention Trial who had reached 8 years of age, more than 50% required special assistance in school or were educated in full-time special education classrooms, and 25% already had repeated at least one grade in school. These data are consistent with those of other observers and indicate that preterm birth disrupts the normal genetically programmed series of events regulating corticogenesis in the developing brain. Intracranial hemorrhage (ICH), or hemorrhage into the germinal matrix tissues of the developing brain, is a major cause of neurodevelopmental handicap …