| Increasing evidence supports the idea that many neurodevelopmental and psychiatric disorders are the result of abnormal brain development, either in the prenatal period or in the first few years of life. Detecting deviations from healthy postnatal developmental trajectories early in life offers an opportunity to identify children who are at increased risk for neurodevelopmental disorders. Use of magnetic resonance imaging (MRI) in a longitudinal study design provides an effective, non-invasive, in vivo method for investigating early stages of brain development in typical and atypical infants.;In the first two postnatal years, cortical thickness and surface area have distinct and heterogeneous patterns of development that are exceptionally dynamic. By age 2, cortical thickness has reached an average of 97% of adult values, compared to surface area, which has reached 69%. Cortical thickness and surface area growth in the first postnatal year is significantly related to general cognitive development. Many of the cortical regions that were found to be significant have been shown to be strongly involved in sensorimotor development and language acquisition, two vital foundations for future cognitive functioning.;Schizophrenia is highly heritable and studying the offspring of schizophrenia patients provides a powerful tool for assessing the effects of genetic liability on early structural brain development. Infants with a high genetic risk for schizophrenia exhibited significant structural differences at both 1 and 2 years of age when compared to typically developing infants. Results from a qualitative analysis also suggest that infants at high genetic risk for schizophrenia may be experiencing a period of accelerated gray matter growth between birth and 1 year, after which cortical growth appears to arrest in high-risk children between 1 and 2 years of age.;Taken together, there is a critical need for a greater understanding of cortical and cognitive development in the first two years of life. As such, this dissertation will have a positive impact because a more complete understanding will lead to more effective early identification strategies and interventions that could attenuate, or even prevent, the progression of neurodevelopmental disorders. |
