In the songbird brain, HVc and its two monosynaptic targets RA and area X are useful models to study brain plasticity. Thus far the volume of these nuclei was determined by histological procedures that obviously make repeated measures impossible. We recently showed that in vivo injection of Mn2+-ions into HVc allows visualizing and accurately delineating RA and area X by Manganese Enhanced-MRI. The present study analyzed the effect of testosterone (T) on the volume of RA and area X and axonal transport dynamics of Mn2+ in female starlings that were implanted with a cannula in the right HVc. Repeated visualization of RA and area X detected a marked volume increase in T-treated birds. The dynamics of axonal transport was altered after T-treatment in the area X, but not in RA. Subsequent analysis of the Mn2+-accumulation based on individual pixels of the MRI images showed an inside-out uptake in RA of both T-treated and controls birds. Mn2+-accumulation was observed in both the medial and lateral parts of are...

Functional magnetic resonance imaging (fMRI) of primary olfactory cortex (POC) has yielded inconsistent results. Odorant-induced POC activity is present at times and absent at others even within the same lab using the same task. Most statistical models used in analysis of fMRI data rely on two assumptions: 1. a monotonic transform from quantity of stimulus to quantity of neural activity, and 2. a linear transform from quantity of neural activity to quantity of MR signal. Whereas the latter has been demonstrated for MR (Boynton et al., 1996), the former has not been demonstrated for POC. Models of temporal encoding, unlike rate-encoding models of olfaction, imply no monotonic transform from quantity of stimulus to quantity of neural activity in POC. Thus, fMRI is potentially invalid as a measure of POC activity under temporal encoding models. To address this we set out to quantify the stimulus intensity-dependence in POC. An olfactometer was used to generate high and low concentrations of the odorants citra...

[Aim] The purpose of this study was to evaluate in the same cat the reproducibility, dependency on stimulus spatial frequency and similarity to the optical intrinsic signal (OIS) of iso-orientation maps obtained from blood oxygenation level dependent (BOLD) and cerebral blood volume (CBV)-weighted functional magnetic resonance imaging (fMRI). [Methods] BOLD-fMRI, CBV-weighted fMRI with monocrystalline iron oxide nanoparticle (10 mg/kg MION) and 570-nm OIS imaging were sequentially performed on the same anesthetized cats. An identical periodic visual stimulation (full-field moving gratings of 4 orientations alternated with homogeneous gray (10 s each) / period) was used in all measurements. Functional MRI at 9.4-Tesla was performed on a 2-cm x 2-cm area parallel to marginal gyrus (area 18) of one hemisphere with a surface coil. The position and orientation of a 1-mm thickness imaging slice (128 x 128 pixels) were determined based on cortical emerging veins with a high resolution venogram. By using Fourier a...

Speculations about the role of free radicals generated in biological systems (so called bioradicals) are commonplace in many recent publications dealing with oxidative stress, inflammation and hypoxia reperfusion. Electron Paramagnetic Resonance Imaging (EPRI) technique has been developed to obtain the spatial distribution of the paramagnetic materials, particularly on a microscopic scale. A large number of biological studies were successfully carried out, especially for the visualization of bioradicals generated in vivo system. Typical example is the detection and visualization of nitric oxide (NO) in septic-shocked animals. The strength of EPRI is that only free radicals are visible in its image. On the contrary, weakness of EPRI is that nothing can be visible except paramagnetic materials on its image. Therefore, it seems imposible to predict in which organs the bioradicals were generated most from the results with EPRI. In order to overcome this problem, in this study, we have started developing EPR/MR...

The spastic Han-Wistar (sHW) rat suffers from glutamate excitotoxicity causing the observed neurodegeneration within the cerebellum (Purkinje cells) and hippocampus (CA3 pyramidal cells). Mutants homozygous for the autosomal trait begin to exhibit motor tremor and hind limb rigidity as early as 25 days of age with progressive ataxic symptoms resulting in mortality at 60 days of age. We hypothesized that this neurodegeneration could be observed non-invasively using magnetic resonance imaging (MRI) and spectroscopy (MRS) of selected brain regions in the sHW rat. Mutant and normal siblings were imaged at 4.7 T using T2- and diffusion-weighted imaging (DWI), and MRS at 25, 40, and 55 days post-natal. Neurodegeneration in the hippocampus, retrospinal and piriform cortices, and cerebellum were quantified and brain volume reductions were calculated. MRS assessment of brain metabolites was limited to the hippocampus. At 55 days, subjects were sacrificed and imaged at 11.7 T for MR microscopy, followed by conventio...

Success of in vivo microelectrode placement is particularly challenging when targeted brain regions are below the cortical surface because stereotaxic locations can vary between individuals. In the past, post-mortem histology was the only technique available to verify the accuracy of electrode placement. More recently, magnetic resonance imaging (MRI) has become widely used but provides only a qualitative account of the relative locations of brain structures and recording cylinders. We have developed a novel technique using MRI to more quantitatively determine electrode trajectories relative to desired anatomical targets. Surgically implanted recording cylinders are fitted with a 7 cm-long plastic tube filled with CuSO4-doped water to aid in the segmentation of the cylinder from brain matter in an MRI volume taken at 1.5T. For slices in which the image of a cylinder can be clearly distinguished from surrounding structures, the cylinder is fit to an ellipse. The mean major and minor axes of all such ellipse...

Diffusion tensor magnetic resonance imaging (DT-MRI) is among the most promising noninvasive imaging techniques, extensively used in brain pathology assessment. Pelizaeus-Merzbacher Disease (PMD) is a disorder linked to a point mutation in PLP/DM20 gene on X chromosome producing an irreversible hypomyelination in affected males. The heterozygous females, carriers of the mutated gene exhibit a transient hypomyelination and oligodendrocyte loss, followed by myelin recovery. The jimpy mouse, a model of human PMD, was used for in vivo DT-MRI brain investigation. Both affected males and female carriers were used to analyze, noninvasively, the sexual dimorphism of white matter in this neurodegenerative disorder and to quantify the hypomyelination and recovery, correlated with histopathology.The myelin loss and regeneration were assessed by calculating and mapping the radial(D⊥) and axial (D‖) water diffusion to axonal tracts, fractional anisotropy (FA) and mean diffusivity. A significant increase of D⊥, caused b...

Considering the close phylogenetic relationship between humans and chimpanzees, it is of particular interest to characterize the age-related changes of the chimpanzee brain that correspond to key foci of pathologic brain aging in humans such as hippocampus, entorhinal cortex, and basal ganglia. Recently, we reported that, unlike aged humans with neurodegenerative pathology, aged great apes have preserved neuron number and cellular volume in layer II neurons of the entorhinal cortex. In the present study, we measured the volume of the hippocampus, caudate nucleus, and putamen from magnetic resonance images (MRIs) of a cross-sectional age-graded sample of postmortem chimpanzee brains. Volumes of interest (VOIs) were measured from either axial T1 weighted or coronal T2 weighted scans, using MRIcro software. VOI measurements were normalized for whole brain volume. Whole brain, raw VOI, and normalized VOI volumes were not correlated with age. ANOVA found no differences in any VOI between age cohorts (19-27 and ...

Brief ischemia leading to selective neuronal death and gliosis induces delayed T1 hyperintensity on MRI in the striatum of humans and rats (Stroke. 1999; 30: 1038-46). The MRI variation may stem from biochemical alterations including Mn-SOD induction in reactive glial cells. To clarify the significance of the MRI modification, we investigated the changes in the striatum of male wistar rats from 4 hours to 4 months after 15-min MCAO with regard to MRI, Mn concentration, neuronal number, immunoreactivities of astrocyte, microglia and Mn-SOD. The behavior study was performed to reveal brain function alteration in relation to the MRI and histological changes. We observed an increase in the T1 signal intensity of the lateral striatum 1 week after ischemia that subsequently decreased from 4 weeks and returned to baseline levels at 16 weeks. Mn-SOD immunoreactivity of glial cells in the lateral striatum increased from the 1st to the 3rd week and decreased from the 4th week after ischemia. The Mn concentration inc...

It has been hypothesized that the auditory system is hierarchically organized, with the primary auditory cortex (AI) encoding the stimulus in the most direct fashion, and upper levels in the hierarchy extracting more complex features of the stimulus. Blood-oxygenation level-dependent functional magnetic resonance imaging was used to investigate the functional organization of the cortical response to various complex, non-speech stimuli, including pure tones, band-passed noise, and upward and downward frequency modulated (FM) sweeps. 15 right-handed normal volunteers performed a one-back task while attending to binaurally presented 30s blocks of the four stimuli classes, each block consisting of stimuli of differing frequencies from the same class. Statistical maps measuring the association between hemodynamic response and stimulus class were made for each subject and combined in stereotaxic space. Bandpass noise showed greater activation than FM sweeps in right auditory cortex and inferior frontal gyrus. Th...