A Thesis submitted to The University of Arizona College of Medicine - Phoenix in partial fulfillment of the requirements for the Degree of Doctor of Medicine. / End‐of‐life (EOL) care and decision‐making in pediatrics is a challenging and complex aspect of patient care experienced by residents and physician attendings. Previous studies have evaluated determinants that contribute to physicians’ attitudes towards EOL care as well as preparedness of students and residents in EOL decision‐making. However, the determinants contributing to a physician’s ability to make such decisions and feel confident in addressing EOL issues are dynamic. Recognizing that decision‐making changes over time, identifying when these changes occur may demonstrate the need for educational interventions for medical students and residents early in their career to help prepare them for EOL decision‐making. A longitudinal assessment of changes in attitudes and knowledge of EOL discussions and how they impact EOL decision‐making was not previously evaluated. This preliminary study establishes a baseline for medical student, resident, and attendings for EOL decision‐making and those factors that contribute to their decisions. This preliminary data has demonstrated a difference amongst attendings compared to residents and students. Despite low probability of survival, residents and students are more likely to select more aggressive management options when compared to attendings. Data obtained after completion of future surveys will show when decision‐making changes, which factors contribute to these changes and their significance in making decisions, and when participants are comfortable addressing EOL care.

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Aging is typically associated with declining mental abilities, most prominent for some forms of memory. There are, however, large inter-individual differences within the older population. Some people experience rapid decline whereas others seem almost spared from any adverse effects of aging. This thesis examined the neural underpinnings of such individual differences by using longitudinal observations of episodic memory change across 15-20 years, combined with structural and functional magnetic resonance imaging of the brain. Study I found significant correlations between volume and activity of the hippocampus (HC), and memory change over a 6-year period. That is, individuals with decline in HC function also had declining memory. In contrast, Study II showed that successfully aged individuals, who maintained high memory scores over 15-20 years, had preserved HC function compared to age-matched elderly with average memory change. The successful agers had HC activity levels comparable to those of young individuals, as well as higher frontal activity. Study III revealed that individual differences in memory ability and brain activity of elderly reflect both differential age-related changes, and individual differences in memory ability that are present already in midlife, when age effects are minimal. Specifically, memory scores obtained 15-20 years earlier reliably predicted brain activity in memory-relevant regions such as the frontal cortex and HC. This observation challenges results from previous cross-sectional aging studies that did not consider individual differences in cognitive ability from youth. Collectively the three studies implicate HC and frontal cortex function behind heterogeneity in cognitive aging, both substantiating and qualifying previous results from cross-sectional studies. More generally, the findings highlight the importance of longitudinal estimates of cognitive change for fully understanding the mechanisms of neurocognitive aging. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Manuscript.</p>

Repeated measures designs are widely used in educational and psychological research to compare the changes exhibited in response to a treatment. Traditionally, measures of change are found by calculating difference scores (subtracting the observed initial score from the final score) for each person. However, problems such as the reliability paradox and the meaning of change scores arise from using simple difference scores to study change. A new item response theory model will be presented that estimates latent change scores instead of difference scores, addresses some of the limitations of using difference scores, and provides a direct comparison of the mean latent changes exhibited by different groups (e.g. females versus males). A simulation-based test was conducted to ascertain the viability of the model and results indicate that parameters of the newly developed model can be estimated accurately. Two sets of analyses were performed on the Early Childhood Longitudinal Study-Kindergarten cohort (ECLS-K) to examine differential growth in math ability between 1) male and female students and 2) Caucasian and African American students from kindergarten through fifth grade.