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The purpose of the present thesis was to examine and quantitatively study key postnatal events in the developing and mature human cerebral cortex within the context of the systematic variation in the laminar structure of the cortex that underlies connectivity patterns and cortical function. To address this, we expanded upon previous work completed by LeRoy Conel and performed extensive analysis of Cresyl-Violet, Cajal, and Golgi-Cox images of various Von-Economo’s Areas for five age groups in order to see where variations in dendritic tree arborization, which is visualized by Golgi-Cox staining, pruning, which is visualized by Cresyl Violet staining, and cytoskeletal changes, which are visualized by Cajal staining, may lie. The results of this analysis showed that across all age groups and cortical types, there are consistently high levels of dendritic tree arborization, cytoskeletal changes, and cell body density changes in all layers across younger age groups, followed by slight declines in older age groups, following the trend of rapid gray matter expansion during the first two years of postnatal life before shifting towards white matter growth. These levels were also the most exaggerated in cortical layers III and V of Agranular, Dysgranular, Eulaminate II, and Eulaminate III areas, suggesting that cortical layers III and V of these areas change the most rapidly during the key events of postnatal development that Conel sought to analyze in his staining experiments. We also found that in layers III and V, Golgi-Cox values increased, reflecting the growth of dendritic trees while Cresyl-Violet and Cajal values decreased, reflecting decreases in cell body density, allowing for increased space between cells, highlighting a complementary inverse relationship that is seen between neurite outgrowth and cell body density. Since postnatal developmental processes in the cortex are largely driven by transcription factors that regulate chromatin expression well into adulthood, we also examined how certain epigenetic modifications in the nuclei of neurons in the adult cortex may explain for variations seen between areas in the analysis of Conel’s images. To address this, we analyzed populations of H4K12 and SC35 expressing pyramidal neurons in layers III and V of Area 46 and Area 32 in order to further understand how patterns of acetylation and RNA splicing may play a role in the rapid changes of layers III and V seen in Eulaminate II and Dysgranular areas. In the case of SC35, higher levels of splicing were seen in layer III of Area 32 and layer V of Area 46, suggesting that splicing centers within the neurons of these layers and areas are more organized. In the case of H4K12, similar levels of acetylation were observed in layers III and V of Area 46 whereas higher levels were observed in layer V of Area 32, indicating a certain degree of regulation of gene expression within these areas. The results of this study demonstrate variations in the timing of the major events of postnatal development across layers in different structural types of cortical areas that correspond to limbic, multimodal, and highly specialized unimodal areas and the inverse relationship seen between neurite outgrowth and changes in cell body density. Additionally, these results demonstrate the impact that patterns of RNA splicing and acetylation may have on these events and can be utilized to identify disruptions in developmental disorders such as autism. / 2024-09-21T00:00:00Z

In the current study, a person-centered approach was taken to the examination of the relation between leader effectiveness and personality preferences. Type Theory and Adaption-Innovation Theory precepts were examined in tandem using cluster analytic techniques in order to discover whether past variable-centered findings relating these two theories would generalize to a person-centered examination. Eight patterns were hypothesized to emerge from the cluster analysis based on past correlational research, and three of these patterns were present in the seven-cluster solution. Leader effectiveness was measured in terms of multisource ratings on Benchmarks™. Hypotheses were proposed based on past variable-centered research examining the relations between Jungian personality types and self, superior, peer, and subordinate ratings of leader effectiveness. Some support was found for the variable-centered predictions, but the pattern-focused approach provided insight into the dynamics of the five personality preferences examined as well as suggested that indicators other than what would be predicted based on variable-centered studies may contribute to perceptions of leader effectiveness. Overall, the results of this study show that, taken together, variable and person-centered approaches to research may help strengthen the sometimes fragile relationship between personality and leader effectiveness. / Ph. D.

The objective of this research was to investigate the nature of landowner supply-response behavior as it related to the land conversion process in the rural-urban fringe. Emphasis was placed on the derivation of the farmer's dynamic supply-response curve of agricultural land for urban uses since the nature of this curve has important implications for land-use policy alternatives in fringe areas. It was argued that the aggregate land market approach to land use policy analysis in the rural-urban fringe is generally inappropriate for practical and theoretical reasons. Consequently, a disaggregated micro model based on the proprietary land unit was developed to explain the land conversion process. The theoretical model is composed of three cost and two demand components. The interaction of these components results in a dynamic supply-response curve of agricultural land for urban uses which is discontinuous over a wide range for many classes of landowners. The theoretical model was tested through discriminant analyses of data collected from a study area where there exists heavy urban demand for agricultural land. The data included information on landowners over time, physical characteristics of the tracts of land, transfer information and· various demand variables. Results of the empirical analyses provided support for the hypotheses incorporated into the theoretical model. Specifically, empirical evidence was found to support the hypotheses that (1) individual farmers' supply response curves are discontinuous over a wide range, (2) farmers' fixed capital investment is a primary cause of the discontinuity, (3) farmers with less fixed capital investment will generally have more elastic supply-response curves which are discontinous over a smaller range, and (4) speculators' supply-response curves will generally be highly elastic and continuous. Various implications of the theoretical model for land-use policy analysis and land-use patterns in the rural-urban fringe are discussed. Particular attention was given to an analysis of Virginia's use-value assessment program based on the theoretical model. It was found that such a program will not "save" agriculture in fringe areas but will raise land price and subsidize speculative activities. Such a program might be more successful in achieving its stated goals if it were implemented in areas on the outlying edge of the rural-urban fringe. / Ph. D.