Understanding the origin and the limitations of the signal intensity changes detected by functional magnetic resonance imaging (fMRI) is critical for full utilization of the capabilities of this technique. This in turn requires an in-depth examination of the physiological basis of fMRI signals. The most commonly used fMRI technique, based on blood oxygenation level dependent (BOLD) effect, is complex and depends on alterations in cerebral metabolic rate of oxygen consumption (CNM02), cerebral blood flow (CBF), and cerebral blood volume (CBV) in response to increased neuronal activity. Contribution of these metabolic and hemodynamic parameters to BOLD is expected to depend on vascular dimensions and geometry as well as experimental parameters such as static magnetic field and spatial resolution. Our understanding of these relationships remains largely qualitative, derives from modeling efforts, and requires additional experimental evaluation. This application aims to bring together expertise in spin-physics, BOLD modeling, and physiology, together with methods utilizing magnetic resonance (MR) imaging and spectroscopy, and different magnetic field strengths (going from 4.7 Tesla to 9.4 Tesla), to focus on investigating the spatiodynamics of vascular and metabolic basis of fMRI signal changes in a well-established animal model. The hypotheses to be tested are: 1) During steady state conditions, regional changes in CMR02 Can be calculated from BOLD and CBF data; and 2) Dynamically, the CMR02 change during neuronal activity is constant except for a transition period in the seconds domain at the onset and the termination of the neuronal stimulation, and the temporal characteristics of the BOLD response is determined by the temporal behavior of CBF and CBV.
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