Date of Award
Spring 1999
Document Type
Dissertation - Restricted
Degree Name
Doctor of Philosophy (PhD)
Department
Biomedical Engineering
First Advisor
Myklebust, Joel
Second Advisor
Jeutter, Dean C.
Third Advisor
Merrill, Stephen
Abstract
For the past several years, developments in magnetic resonance imaging have resulted in techniques that enhance spatiotemporal resolution and expedite formation of images. These techniques, generically termed functional magnetic resonance imaging (fMRI), have capability to detect endogenous cerebral contrast noninvasively within the cerebral regions in response to external (e.g., somatosensory and visual) stimuli, the contrast depending on blood oxygenation level dependent (BOLD) effects and increased blood flow. Previous experiments implicitly demonstrated the localizations of stimulated neuronal regions based on the locations of detected endogenous contrast. However, there are two problems: First, the connection between the activated neurons and the contrast is obscure. Second, the hemodynamic responses are far greater than the stimulated neuronal responses, thus indicating that the temporal relations between activated regions in fMRI are unknown. The fMRI provides excellent spatial topography of activated brain regions but modest temporal characteristics, whereas the EEG has better temporal resolution but limited spatial resolution. Thus, cerebral regions shown in the fMRI appear at certain times given by the EEG, providing the paths of processing neurons from one region to another. Consequently, the combination of EEG and fMRI may confirm the spatial relation between the regions of activated neurons and endogenous cerebral contrast and may provide the temporal relation between them. However, a model is required to locate such stimulated regions from EEG...