Morphological analysis of cerebral cortex based on magnetic resonance imaging in the elderly
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Aging is generally associated with cognitive decline and the increased probability of a specific disease, such as Alzheimer's disease (AD). Despite intensive research into the aging brain, the mechanisms underpinning cognitive aging and the risk factors for AD still remain unknown. Magnetic resonance imaging (MRI) has been used as a valuable non-invasive technique for detecting changes within the brain in vivo. Several researches have already applied computer-based brain morphometry techniques based on MRI. Most previous studies focus on measuring cortical thickness or brain volume, while few studies examine features of the cortical sulci, which embed at least two distinct sources of genetic influences. The goals of this dissertation are to use novel computer-based morphometry techniques in T1-weighted scans in the elderly to reveal cortical sulcal variability with aging, cognitive decline, and earlier-stage AD, in order to assist with the prevention of cognitive disorders. There are three sub-projects within this dissertation. Firstly, using automated methods, we measure the global sulcal indices (g-SIs) of both cerebral hemispheres and the average sulcal span in five prominent sulci from a large community cohort of 319 non-demented individuals aged 70-90 years. Our findings suggest that both age and sex contribute to significant cortical gyrification differences and variations in the elderly. The first study establishes a reference for future studies of age-related brain changes and neurodegenerative diseases in the elderly. Secondly, we examine the relationship between cortical features and cognitive function in the same sample. To our knowledge, this is the first study to examine three-dimensional cortical sulcal patterns in community-dwelling elderly with multiple cognitive domains. The results showed the cognitive performances were correlated with sulcal features but not with cortical thickness. The findings suggest that regionally specific sulcal morphology is associated with cognitive function in elderly individuals. In the third study, we investigate sulcal morphology and cortical thickness in earlier-stage AD. The results suggest that abnormalities of the cortical sulci are characteristic of patients with even very mind AD, and could facilitate early diagnosis of the condition. In summary, we found changes in brain structure, especially the cortical surface, are associated with aging, cognitive decline, and AD. The novel sulci features may contribute to building biomarkers of cognitive decline and AD, and ultimately to assisting with the prevention of cognitive disorders.
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