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Title Analysis of functional Magnetic Resonance Imaging : Activation Changes Related to Cataract Surgery
Author Baruel Johansen, Louise
Linde Reislev, Nina
Supervisor Hansen, Lars Kai (Cognitive Systems, Department of Informatics and Mathematical Modeling, Technical University of Denmark, DTU, DK-2800 Kgs. Lyngby, Denmark)
Institution Technical University of Denmark, DTU, DK-2800 Kgs. Lyngby, Denmark
Thesis level Master's thesis
Year 2010
Abstract This project is concerned with the analysis of functional Magnetic Resonance Imaging (fMRI) in the brain of elderly subjects affected by cataract. The objective is to examine the changes in visual cortex activity after monocular cataract surgery. The subjects are scanned three times; before surgery, 2 days after surgery and again 6-8 weeks after surgery, which makes it possible to evaluate the changes in visual input and the functional activity as measured by Blood Oxygen Level Dependent (BOLD) sensitive fMRI. The experimental procedures and stimuli paradigm are designed to enable retinotopic mapping, based on eccentricity and polar mapping experiments. The methods applied are statistical parametric mapping approaches based on a general linear model. From the model parameters of a first-level analysis, the average delay of the haemodynamic response is detected to be approximately 3 s. On the basis of the first-level analysis, 6 subjects are excluded from further analysis due to lack of response and excessive movement during scanning. In general the brains of the elderly subjects are characterised by severe atrophy. We detect significant changes (family-wise error p < 0:05) in the visual cortex using a random-effects model across subjects. Furthermore, we investigate changes in the point-to-point mapping from the visual field to the visual cortex over time. For voxels located centrally in the visual cortex, we demonstrate a general signal increase. A shift towards central vision in the point-to-point mapping is observed. For each subject we furthermore investigate the correlation between visual field sensitivity (scotomas) as measured by standard visual field tests and measures of sensitivity based on the fMRI response. However, this correlation analysis reveals no signicant eects across subjects. These results present evidence that the change in visual cortex predominantly is explained by a correction of light dispersion, activating central voxels after surgery.
Imprint Technical University of Denmark (DTU) : Kgs. Lyngby, Denmark
Series IMM-M.Sc.-2010-20
Fulltext
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Admin Creation date: 2010-04-21    Update date: 2010-10-28    Source: dtu    ID: 260008    Original MXD