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▼a Although there has been a surge of research on neural development in early childhood over the last few decades, little research has focused specifically on toddlers. The current study aimed to improve our understanding of neural development in toddlerhood, through applying a developmental approach to studying event-related potentials (ERPs). A community sample of 190 toddlers were assessed at ages 30, 36, and 42 months. At each age, ERP data were collected from two different computerized tasks aimed at assessing self-regulation, a Go/NoGo task and a Passive Auditory Oddball task. From the Go/NoGo task, the NoGo N2 component, which is thought to index response inhibition, was extracted. From the Passive Auditory Oddball task, the Target P3 component, which is thought to index attentional processing, was extracted. Additionally, at each age, children participated in a variety of behavioral self-regulation tasks, including three tasks assessing response inhibition: the Bird/Alligator task (a modification of the Bear/Dragon task), the Grass-Snow task, and the Fruit-Stroop task, and several tasks assessing attention: a Sustained Attention task and the Token Sort task. At the 30 month assessment, several observer-report and parent-report measures assessing the child's home environment were collected. Study 1 aimed to explore developmental changes in the morphology of the N2 and P3 components across toddlerhood, examining both rank-order stability and mean-level change. Findings suggest that there were higher levels of rank-order stability in amplitudes (as compared to latencies), from 36 to 42 months (as compared to 30 to 36 months), and in the N2 component (as compared to the P3). However, the rank-order stability across ERP components and measurement occasions was relatively modest in size. Longitudinal growth curve analysis, conducted in a Structural Equation Modeling framework, was used to examine within-child changes in the NoGo N2 and Target P3 ERP component amplitude and latency. Findings indicated that a random-intercepts model was the best fitting model for both component's amplitude and latency values, suggesting that there was no significant change in either amplitude or latency for either component across this year of development. Study 1 also aimed to examine if the morphology of the N2 and P3 component was associated with stability and change in performance on the behavioral self-regulation tasks assessing response inhibition and attention. Latent growth curve analysis indicated that performance on all five of the behavioral tasks significantly improved from 30 to 42 months. When cross-domain latent growth curve analysis was used to examine the association between the latent growth models of the components and the latent growth models of the behavioral tasks, only the association between P3 component amplitude and change in performance on the Token Sort task was significant. Study 2 aimed to examine how features of a child's early environment alter the trajectory of neural development across toddlerhood. A cumulative risk index, combining risk factors across multiple domains of risk (including biological risk factors [e.g., illnesses, sleep deficits], socioeconomic risk factors [e.g., parent job loss, family socioeconomic status], and environmental/familial risk factors [e.g., crowdedness of the home environment, maternal depression]), was created based on parent- and observer-reports at 30 months of age. The cumulative risk index, and each domain of risk in isolation, were examined as predictors of the latent intercept identified by the fitted latent growth models of N2 and P3 latency and amplitude. Only the association between early environmental/familial risk and N2 latency were significant. Findings suggest that higher levels of exposure to early environmental/familial risk were associated with longer N2 latencies. Despite a handful of significant findings, few of the hypothesized patterns of association emerged in the current study. Several factors that might explain the current study's largely non-significant findings are explored, including high levels of missingness, low signal-to-noise ratios, and small time windows between assessments. However, the highly unique nature of the current study's data, which examines a sample of toddlers longitudinally, combines both electrophysiological and behavioral assessments of self-regulation, and includes a thorough assessment of the child's home environment (including both parent and observer-report), makes even these null findings an important and novel contribution to the literature. |