Neural correlates of cognitive impairment in aging: Examining hippocampal dysfunction and cerebrovascular disease

The broad aim of this dissertation is to use structural and functional neuroimaging techniques to identify and understand biological markers for cognitive decline in the elderly. Specifically, the focus is on the roles that cerebrovascular disease and hippocampal dysfunction play in producing cognitive impairment. In Chapter 1, the incidence of these two markers was examined in a community-based sample of elderly individuals with a wide range in cognitive abilities. The aim of this study was to investigate whether these structural brain changes were seen in individuals prior to the development of dementia, and how these changes were related to the presence of dementia. In Chapter 2, the focus was on individuals with Mild Cognitive Impairment (MCI), a clinical characterization of elderly individuals with episodic memory impairments beyond what is expected in normal aging. Hippocampal dysfunction and cerebrovascular disease were investigated as potentially different etiologies for episodic memory impairment. In Chapter 3, functional MRI was used to investigate the underlying mechanism of how cerebrovascular disease can lead to memory impairment. In brief, the findings from these studies suggest that cerebrovascular disease and hippocampal dysfunction both play important, but different roles in producing cognitive impairment and that the two may work synergistically to greatly increase the risk for developing dementia. The dissertation concludes with a general discussion of the significance and implications of these findings to aging and dementia research and future directions are suggested.