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Functional neuroimaging in animal models is essential for understanding the principles of neurovascular coupling and the physiological basis of fMRI signals that are widely used to study sensory and cognitive processing in the human brain. While hemodynamic responses to sensory stimuli have been characterized in humans, animal studies are able to combine(More)
Recent MRI studies at high field have observed that, in certain white matter fiber bundles, the signal in T(2)*-weighted MRI (i.e. MRI sensitized to apparent transverse relaxivity) is dependent on fiber orientation θ relative to B(0). In this study, the characteristics of this dependency are quantitatively investigated at 7 T using ex-vivo brain specimens,(More)
T(2)*-weighted gradient-echo MRI images at high field (≥ 7T) have shown rich image contrast within and between brain regions. The source for these contrast variations has been primarily attributed to tissue magnetic susceptibility differences. In this study, the contribution of myelin to both T(2)* and frequency contrasts is investigated using a mouse model(More)
In vivo tractography based on diffusion magnetic resonance imaging (dMRI) has opened new doors to study structure-function relationships in the human brain. Initially developed to map the trajectory of major white matter tracts, dMRI is used increasingly to infer long-range anatomical connections of the cortex. Because axonal projections originate and(More)
Information about layer specific connections in the brain comes mainly from classical neuronal tracers that rely on histology. Manganese Enhanced MRI (MEMRI) has mapped connectivity along a number of brain pathways in several animal models. It is not clear at what level of specificity neuronal connectivity measured using MEMRI tracing can resolve. The goal(More)
High field (> or =7 T) MRI studies based on signal phase have been used to improve visualization of the fine structure of the brain, most notably the major white matter fiber bundles, the gray-white matter subdivision, and the laminar cortical architecture. The observed contrast has been attributed in part to local variations in magnetic susceptibility(More)
MRI at high field can be sensitized to the magnetic properties of tissues, which introduces a signal dependence on the orientation of white matter (WM) fiber bundles relative to the magnetic field. In addition, study of the NMR relaxation properties of this signal has indicated contributions from compartmentalized water environments inside and outside the(More)
Present noninvasive neuroimaging methods measure neuronal activity indirectly, via either cerebrovascular changes or extracranial measurements of electrical/magnetic signals. Recent studies have shown evidence that MRI may be used to directly and noninvasively map electrical activity associated with human brain activation, but results are inconclusive.(More)
Hypertension afflicts 25% of the general population and over 50% of the elderly. In the present work, arterial spin labeling MRI was used to non-invasively quantify regional cerebral blood flow (CBF), cerebrovascular resistance and CO(2) reactivity in spontaneously hypertensive rats (SHR) and in normotensive Wistar Kyoto rats (WKY), at two different ages (3(More)
Reactive astrogliosis occurs after diverse central nervous system (CNS) insults. While astrogliosis provides protection against inflammation, it is also obstructive in the progress of neuranagenesis after CNS insults. Thus, a method that enables in vivo visualization and tissue characterization for gliosis would be invaluable for studies of CNS insults and(More)