Introduction:Functional magnetic resonance imaging (fMRI) provides an indirect measure of cerebral activation via changes in blood-oxygen-level-dependent (BOLD) signal,which assumes a coupling between neural activity and tissue oxygenation changes.We sought to determine whether blood pressure(BP) changes contribute to functional activation detected by fMRI.Methods:Images were acquired in rats using a 9.4T MR system prior to and following a BP increase or decrease with and without electrical stimulation of the forepaw.Four BP ranges were investigated (1-30,31-45,46-60 and >60 mmHg).Transient BP increases were produced with norepinephrine (e.g.0.15-1.2ug/kg,I.V.)and decreases with arfonad (e.g.0.5-3.25mg/kg,I.V.).Fuzzy clustering (EvIdent) and cross-correlation analysis were used to identify voxels of apparent activation in response to stimulation or the BP time course measured arterially.Results: Electrical stimulation of the forepaw produced activation in the sensory-motor cortex.This activation increased ...

Absence seizures are impairments of consciousness with 3 Hz spike-wave discharges (SWD) on EEG. To elucidate the neuroanatomy responsible for these behavioral and EEG effects, manganese enhanced MRI (MEMRI) was completed. Mn2+ is a Ca2+ analog and MR contrast agent that has been used to non-invasively visualize Ca2+-dependent neural activity. A unique property of Mn2+ is that once internalized it is transported transynaptically via functional connections of neurons. This study was designed to uncover the functional neuroanatomical circuit causing absence epilepsy. Rats were stereotaxically implanted with a cannula in the somatosensory cortex (peri-oral area). Rats were then given an i.p. injection of vehicle or γ-butyrolactone (GBL, used to induce the absence seizure). Five minutes after GBL/vehicle administration rats were microinjected with 100nl of 100mM MnCl2 into the somatosensory cortex. The SWDs characterizing the seizure were maintained for 8 hours by repeated injections of GBL to allow sufficient ...

We used functional Magnetic Resonance Imaging (fMRI) to assess motor recovery in a patient with left middle cerebral artery (MCA) stroke. The patient was scanned on three occasions, at one-month intervals using a finger-sequencing paradigm consisting of both overt movement and movement imagery. Each of these finger-to-thumb opposition tasks were carried out in a prescribed sequence and consisted of three conditions, two unimanual and one bimanual. Although the first session showed more ipsilateral sensorimotor cortex activation during movement using the affected hand, later sessions exhibited more contralateral activation, which conforms to the pattern of the vascular response in normal subjects. However, blood flow to ipsilateral parietal cortex increased over sessions, suggesting that the undamaged parietal cortex took over the function of the affected side, even after improved blood flow to the contralateral sensorimotor cortex. Stronger activation was observed in the motor cortex of the lesion side and...

Optical imaging spectroscopy (OIS), laser Doppler flowmetry (LDF) and magnetic resonance imaging (MRI) were used to investigate the hemodynamic response to neural activation in rat barrel cortex. The MRI measurements were made at 3T in a small animal magnet facility (Magnex with MRRS console). Both fMRI measurements of the BOLD signal and cbv-MRI estimates of changes in blood volume (CBV) were obtained concurrently with measurements of CBF using a magnet compatible LDF probe (Perimed) following both electrical stimulation of the whisker pad (16s,1.2mA @5Hz) and hypercapnic challenge (120s @10% CO2). MRI measurements were obtained using a GRE-EPI sequence at a voxel resolution of 470x470x2000µm. Of necessity, cbv-MRI data was collected after BOLD measurements following infusion of the contrast agent AMI-227 (10mgFe/kg ~200µmol Fe/kg). The BOLD and cbv-MRI data from the hypercapnic challenges were used to estimate the baseline scaling term M=TE.A.CBV0.[Hbr]βv0 used in the biophysical model of the BOLD signal...

Our previous study using functional magnetic resonance imaging (MRI) suggests that the medial prefrontal cortex (mPFC), which is not considered as one of the olfactory centers, responded well to olfactory stimulations similar to the ventrolateral primary olfactory cortex (i.e., the piriform cortex and olfactory tubercle). The present study was aimed to investigate neural projections from olfactory cortices to mPFC by using manganese-enhanced MRI (MEMRI), a newly developed in vivo neural tracing technique. Rats were anesthetized and MnCl2 (100 mM, 0.2-0.5 μl) was injected stereotaxically by using a glass micropipette into several parts of olfactory pathway. Injection of Mn2+, a biological calcium analogue and paramagnetic tract tracing agent, allows highlighting specific brain areas that are active. T1-weighted multislice spin-echo images were acquired at 8 h and 24 h after Mn2+ injection using SMIS MRI system, consisted of a 4.7 T/400 horizontal superconducting magnet equipped with actively shielded gradie...

Introduction The dopamine transporter (DAT) is an important target for drugs of abuse such as cocaine as well as a therapeutic target for such conditions as narcolepsy (amphetamine) and attention deficit hyperactivity disorder (ADHD treated with ritaline or methylphenidate). Although these drugs all target the dopamine transporter, they have different behavioral effects and different affinities for the norepinephrine transprter as well as the serotonin transporter. We compared the response to four different dopamine transporter ligands to ascertain the regional differences that may exist in the activation patterns. These differences may help explain some of the relative behavioral effects. Methods Four DAT ligands were used in phMRI studies: Cocaine(1mg/kg iv, n=32); Methylphenidate(MPH, 2mg/kg iv, n=6); CFT(0.75mg/kg iv, n=4); nomifensene(NMFS, 2mg/kg iv n=6). IRON method (1) were used to obtained relative cerebral blood volume(rCBV) changes. We quantified rCBV changes in fronto-parietal cortex (FCtx), th...

The aim of our study is to develop non invasive approaches to follow the fate, viability and migratory potential of progenitor cells following transplantation using super high resolution positron emission tomography (PET) and magnetic resonance imaging (MRI). We labeled rat subventricular zone (SVZ) progenitor cells and control cell line (PC12, pheochromocytoma cells) using 18F-fluorodeoxyglucose for PET studies and dendrimer-encapsulated super paramagnetic particles (Feredex) for MRI. These labeled cells were transplanted into the striatum or rostral migratory stream (RMS) of normal and 6-OHDA lesioned rats. During a period of 2 months, transplanted progenitor cells were easily identifiable with MRI. SVZ cells implanted into the RMS migrated after one week retention time toward olfactory bulb as seen with MRI. Slow migration of the cells implanted into the striatum was observed after 3 weeks. Histological analyses using Nissl, Iron stain, H&E and Fluoro-Jade, allowed delineation of the transplantation sit...

The combination of functional and spectroscopic MRI with invasive measurements of neural activity in monkeys may help us investigate levels of neural organization revealing both how networks are organized and how small assemblies contribute to this organization. Insights can be gained into long-range neural interactions, learning-related neurochemical changes, dynamic connectivity by means of MR labeling techniques, and plasticity and reorganization following lesions. Insights are also gained into the relationship between the fMRI signal and the underlying neuronal activity that we think it represents. In my talk I’ll describe such applications and discuss their contribution in our understanding of neural mass activity.

Although fMRI of the whole brain is routinely performed in humans, there are few reports of whole brain fMRI in rodents, due in part to the need for high spatial and temporal resolution. Instead, most rodent studies have focused on the primary sensory cortex. We have developed an 11.7 T MR imager for animals that can provide the high spatial and temporal resolution necessary for whole brain fMRI in rodents. We performed whole brain imaging in the rat during electrical stimulation of the forepaw. Functional MR images with BOLD contrast were obtained in 11 rats during forepaw stimulation (90 s rest, 45 s stimulation, 90 s rest). An echo planar imaging sequence with interleaved slices was used to image the entire brain every 1.5 seconds, from olfactory bulb to cerebellum, with an in-plane resolution of 300 microns. Excellent image quality with single shot echo planar imaging was achieved even at this high magnetic field by optimizing the MR imaging sequence and hardware. Activation was observed in the primary...

Introduction: In the brain of premature infants primary intracerebral hemorrhage (ICH) is a common occurrence. It is usually unilateral and deep in the cerebrum near the ganglionic eminence beside the lateral ventricle. Blood can extend into the ventricles causing hydrocephalus. Even small lesions of this type, are associated with poor developmental outcome including cerebral palsy and mental retardation. The purpose of this study was to obtain magnetic resonance images (MRI) of the mouse brain after ICH and to correlate the images with histological evolution. Methods: ICH was induced in one-day-old mice, which are developmentally similar to a 24-26 weeks human fetus, by injection of autologous blood into the striatum. MRI was obtained 15 minutes to 48 hours later. Mice were perfused with 4% paraformaldehyde 8 hours to 28 days later. H&E, immunohistochemical, and TUNEL staining were used to quantify the lesion area, neutrophils, microglia, and cell death at the edge of the hemorrhagic lesion. Results: Hist...