Developmental Trajectories of Brain Structure, Motor, and Cognitive Functions from Infancy to Early Childhood and the Impact of SES
Type of DegreePhD Dissertation
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During the first years of life, there are significant brain, cognitive, and motor development changes. Although studies have suggested a bidirectional relationship between the brain and these functional outcomes, few studies have directly examined their relationships. Moreover, the literature has suggested that socioeconomic status (SES) and related variables impact the brain, cognitive, language, and motor development. Additionally, parental stress has been associated with negative impacts on child development. However, there are knowledge gaps concerning the longitudinal relationships between the brain, motor, and cognitive development during the first few years of life, as well as the influence of socioeconomic factors and parental stress and their impact on these domains. Therefore, the overarching purpose of this dissertation was to address these knowledge gaps by examining the developmental trajectories of brain structure, motor skills, and cognitive function and their relationships from infancy to early childhood (i.e., birth – 2.5 years). In addition, this study examined the impact of adjusted household income and parental stress on the development of each domain. Lastly, we determined if changes in brain structure mediated the effect of adjusted household income and parental stress on this population's motor skills and cognitive function. To this end, a secondary data analysis was conducted using data from the National Institute of Health Study of Normal Brain Development – Object 2. We verified a significant positive relationship between average cortical thickness (CT) and BSID-II motor scale scores; however, there was an inverse relationship between average CT and BSID-II mental scale scores. Moreover, total cortical grey matter (GM) volume was not a significant predictor of motor or cognitive development. In addition, adjusted household income was a significant predictor of total cortical GM volume, and parental stress significantly predicted average CT and total cortical GM volume. However, these variables were not significant predictors of motor or cognitive development. Given the lack of relationship between the adjusted income and parental stress on the behavioral outcomes, the mediation analyses were not supported. Indeed, if total cortical GM volume or average CT were included in the model, there was still no evidence of a relationship between household income or parental stress on motor or cognitive development. Future directions and limitations are discussed. The study provided evidence regarding the developmental trajectories of each domain and the impact of income and parental stress. This study represents an important step in understanding infant development from a more comprehensive perspective.