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Spatial specificities of the calcium-dependent synaptic activity, hemodynamic-based blood oxygenation level-dependent (BOLD) and cerebral blood flow (CBF) fMRI were quantitatively compared in the same animals. Calcium-dependent synaptic activity was imaged by exploiting the manganese ion (Mn++) as a calcium analog and an MRI contrast agent at 9.4 T.(More)
The nature of vascular contribution to blood oxygenation level dependent (BOLD) contrast used in functional MRI (fMRI) is poorly understood. To investigate vascular contributions at an ultrahigh magnetic field of 9.4 T, diffusion-weighted fMRI techniques were used in a rat forepaw stimulation model. Tissue and blood T(2) values were measured to optimize the(More)
The blood oxygenation level-dependent (BOLD) contrast mechanism can be modeled as a complex interplay between CBF, cerebral blood volume (CBV), and CMRO2. Positive BOLD signal changes are presumably caused by CBF changes in excess of increases in CMRO2. Because this uncoupling between CBF and CMRO2 may not always be present, the magnitude of BOLD changes(More)
Visualizing brain anatomy in vivo could provide insight into normal and pathophysiology. Here it is demonstrated that neuroarchitecture can be detected in the rodent brain using MRI after systemic MnCl2. Administration of MnCl2 leads to rapid T1 enhancement in the choroid plexus and circumventricular organs, which spreads to the CSF space in ventricles and(More)
A multislice EPI sequence was used to obtain functional MR images of the entire rat brain with BOLD contrast at 11.7 T. Ten to 11 slices covering the rat brain, with an in-plane resolution of 300 microm, provided enough sensitivity to detect activation in brain regions known to be involved in the somatosensory pathway during stimulation of the forelimbs.(More)
Development of efficient imaging techniques to trace neuronal connections would be very useful. Manganese ion (Mn2+) is an excellent T1 contrast agent for magnetic resonance imaging (MRI). Four reports utilizing radioactive Mn2+ in fish and rat brain indicate that Mn2+ may be useful for tracing neuronal connections. Therefore, the purpose of this work was(More)
Manganese-enhanced MRI (MEMRI) is being increasingly used for MRI in animals due to the unique T1 contrast that is sensitive to a number of biological processes. Three specific uses of MEMRI have been demonstrated: to visualize activity in the brain and the heart; to trace neuronal specific connections in the brain; and to enhance the brain cytoarchitecture(More)
The close correspondence between neural activity in the brain and cerebral blood flow (CBF) forms the basis for modern functional neuroimaging methods. Yet, the temporal characteristics of hemodynamic changes induced by neuronal activity are not well understood. Recent optical imaging observations of the time course of deoxyhemoglobin (HbR) and(More)
The model used for calculating perfusion by MRI techniques that use endogenous water as a tracer assumes that arterial water is a freely diffusible tracer. Evidence shows that this assumption is not valid in the brain at high blood flow rates, at which movement of water into and out of the microvasculature becomes limited by diffusion across the blood-brain(More)
The extraction fraction of vascular water in rat brain is investigated by means of diffusion measurements of arterial spin labeled water at varying cerebral blood flow (CBF) values. The apparent diffusion coefficient (ADC) of the difference of the proton magnetization signal in the brain acquired with and without continuous arterial spin labeling is modeled(More)