UC San Diego

Children born before 33 weeks of gestation have an increased risk for early brain injury, as well as cognitive, behavioral, and academic deficits. The aim of this dissertation was to contribute to a more comprehensive understanding of brain and cognitive development following preterm birth. All three studies used data from a cohort of children recruited before starting kindergarten (5 years of age) who were followed up after one and two years. At each timepoint, children completed structural and diffusion weighted MRI, as well as a battery of cognitive and behavioral tests. Forty-seven to 51 children born preterm (24–32 weeks gestational age), and 27 to 28 children born full-term were included in each study.The first study examined the effect of preterm birth on number and arithmetic skills, and how it is mediated by related cognitive functions. Number and arithmetic skills were lower in children born preterm. The performance gap in number skills decreased over time, while the performance gap in arithmetic skills increased. The effect of preterm birth on number and arithmetic skills was mediated by phonological processing, visual-motor integration, and inhibitory control, but not spatial working memory. Phonological processing showed the strongest mediating effect. The second study examined the effect of preterm birth on development of subcortical gray matter and white matter volumes, and diffusivity measures of white matter tracts. Children born preterm had smaller volumes of thalamus, brain stem, cerebellar white matter, cingulum, corticospinal tract, inferior frontal occipital fasciculus, uncinate fasciculus, and temporal superior longitudinal fasciculus, while their ventricles were larger compared to full-term controls. We found no significant effect of preterm birth on diffusivity measures. Despite developmental changes and growth, group differences were present and similarly strong at 5, 6, and 7 years. The third study examined the association between white matter tract diffusivity measures and mathematics skills at 5 and 7 years of age. Fractional anisotropy of the right and left corticospinal tract, left inferior longitudinal fasciculus, and left inferior frontal occipital fasciculus showed a significant interaction effect with term status. This moderating effect of preterm birth may be indicative of reorganization and plasticity of functional networks following early injury due to prematurity. These findings help to delineate the developmental trajectory of brain and cognitive development during early childhood following preterm birth. This knowledge may provide guidance for opportunities for support of children born preterm and their families, such as targeted evaluation and use of interventions.