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An NMR method is applied for separating blood volume and magnetic susceptibility effects in response to neuronal stimulation in a rat model. The method uses high susceptibility contrast agents to enhance blood volume induced signal changes. In the absence of exogenous agent, the dominant source of signal change on neuronal activation is associated with the(More)
A simple model is presented that allows quantitative separation of the contributions of signals from water in blood and extravascular parenchyma due to changes in blood oxygenation, induced either by brain activation or by alteration of inspired oxygen. The separation is based on the progressive attenuation of the signals in the vasculature of different(More)
Quantitative magnetic resonance imaging (MRI) and spectroscopy (MRS) measurements of energy metabolism (i.e. cerebral metabolic rate of oxygen consumption, CMR(O2)), blood circulation (i.e. cerebral blood flow, CBF, and volume, CBV), and functional MRI (fMRI) signal over a wide range of neuronal activity and pharmacological treatments are used to interpret(More)
The factors affecting the rate of loss of transverse magnetization in gradient echo and spin-echo pulse sequences have been quantified using computer modeling for media containing arrays of susceptibility variations. The results are particularly relevant for describing the signal losses that occur in tissues containing capillaries of altered intrinsic(More)
Functional NMR imaging of the brains response to a simple visual task has been performed using a fast spin echo (FSE) imaging sequence at 1.5 T. The FSE method refocuses dephasing effects induced by large-scale susceptibility variations, and permits imaging in regions where macroscopic field gradients produce artifacts in gradient echo sequences. At 1.5 T,(More)
An animal model of sensory activation using fMRI at 2.0 T has been developed, demonstrating that fMRI studies on animals need not be limited to high field magnets. These methods produced reliable image intensity changes of 2% using median nerve stimulation in rats at 3 Hz and propofol as the anesthetic agent. At 6 Hz the activation was slightly but not(More)
Brain blood volume changes in the rat in response to 5-HT(1A) agonist and antagonist administration were measured using susceptibility contrast enhanced magnetic resonance imaging (MRI). Administration of the 5-HT(1A) agonist 8-OH-DPAT resulted in decreases in fractional brain blood volumes. Administration of the 5-HT(1A) antagonist WAY-100635 following a(More)
Near infrared optical topography (OT) is the simultaneous acquisition of hemoglobin absorption from an array of optical fibers on the scalp to construct maps of cortical activity. We demonstrate that OT can be used to determine lateralization of prefrontal areas to a language task that has been validated by functional MRI (fMRI). Studies were performed on(More)
The blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) method, which is sensitive to vascular paramagnetic deoxyhemoglobin, is dependent on regional values of cerebral metabolic rate of oxygen utilization (CMR(O2)), blood flow (CBF), and volume (CBV). Induced changes in deoxyhemoglobin function as an endogenous contrast(More)
Magnetic resonance imaging (MRI) and spectroscopy (MRS) were used at a magnetic field strength of 7 T to measure CBF and CMRO2 in the sensorimotor cortex of mature rats at different levels of cortical activity. In rats maintained on morphine anesthesia, transitions to lower activity and higher activity states were produced by administration of pentobarbital(More)