Several neurodegenerative disorders such as Alzheimer’s disease (AD) are associated with elevated iron accumulation. It is not currently understood whether the iron accumulation in the AD brain is the cause of the neurodegeneration associated with the disease. Here we use T2 weighted and T2* weighted imaging to render sensitive and accurate R2* mapping for quantitative iron measurement with a 3.0T magnet. The attached figure demonstrates the MR imaging of the mouse brain. The left image is a T2 weighted image and the right a T2* parameter map. Areas high in iron content (such as the Substantia Nigra) show as hypo-intense compared to surrounding tissue. This work aims at in vivo quantitative measurement of the iron content of mice models of Alzheimer’s disease. There is a good correlation between the T2* map and the histochemically iron stained sections. These results will allow for quantitative iron measurement and the development of a calibration curve comparing T2* relaxation times to iron concentration ...

OBJECTIVE: To assess the prevalence of microhemorrhages (MHs) possibly related to cerebral amyloid angiopathy (CAA) among consecutive patients undergoing MR imaging in a memory disorders unit. BACKGROUND: The estimated prevalence of neuropathological CAA and CAA-related hemorrhages in Alzheimer's disease (AD) is 80-98% and 5-7% respectively. While CAA cannot be directly detected during life, MHs characteristic of CAA can be sensitively imaged by gradient-echo (GE) MRI. The presence of multiple strictly lobar hemorrhages without other cause (Probable CAA) is a specific marker for advanced CAA. DESIGN/METHOD: All patients age 55 or greater from the Massachusetts Alzheimer's Disease Research Center (MADRC) Patient Registry database who underwent initial dementia evaluation with GE MRI at our center between January 2001 and September 2003 were retrospectively reviewed. RESULTS: Of 61 eligible patients, 21 (34%) had hypointensities on GE MRI, 7 (11%) meeting criteria for Probable CAA, and an additional 2 showed...

An internal model is a neural mechanism that can mimic the input–output properties of a controlled object such as a tool. Recent research interests have moved on to how multiple internal models are learned and switched under a given context of behavior. Two representative computational models for task switching propose distinct neural mechanisms, thus predicting different brain activity patterns in the switching of internal models. In one model, called the mixture-of-experts architecture, switching is commanded by a single executive called a “gating network,” which is different from the internal models. In the other model, called the MOSAIC ( MO dular S election A nd I dentification for C ontrol), the internal models themselves play crucial roles in switching. Consequently, the mixture-of-experts model predicts that neural activities related to switching and internal models can be temporally and spatially segregated, whereas the MOSAIC model predicts that they are closely intermingled. Here, we directly ex...

A special area, the marginal division (MrD), has been found at the caudomedial border of rat striatum in 1988 by Shu et al. It consists of fusiform neurons and is densely filled of many neuropeptide fibers and terminals. The MrD has been also identified in the neostriatum of cat, monkey and human brains. Learning and memory function of the MrD has been verified by Y-maze test in rats. In order to investigate the function of the MrD in human brain, functional magnetic resonance imaging (fMRI) of healthy volunteers tested with an auditory digital working memory task was performed. Highly active areas were observed in the prefrontal cortex and MrD with left sided predominance during performance of the task, but other parts of the neostriatum were not excited and the MrD was not activated in a control test of non-working memory. The results indicate that the MrD participate the auditory digital working memory of human brain. Clinical case investigation combining MRI and cognitive function analyses exhibited th...

fMRI based on gradient echo (GE) BOLD effect is the most widely used method for studying brain function non-invasively in vivo. It is not clear, however, whether the spatial specificity of GE-BOLD fMRI could provide a viable tool for the investigation of cortical micro-organization, and whether alternative fMRI modalities such as CBF fMRI could be more suitable than GE-BOLD fMRI for this goal. To address this question, we investigated the lateral point spread function (PSF) in the cat visual cortex (area 18) with GE-BOLD and CBF fMRI on the same cats. All experiments were performed at ultra-high magnetic field, 9.4 T. Four anesthetized cats (1.45 ~ 1.95 kg) were monocularly stimulated with sinusoidal wave gratings (0.15 cyc/deg, 2 Hz). Contiguous areas of the upper- and lower visual fields were alternately stimulated. The activation maps of GE-BOLD and CBF were analyzed, and the border between the areas activated by the stimulation of the upper and the lower visual fields was detected. Lateral PSFs of GE-B...

In an attempt to reconcile any differences between fMRI BOLD responses and neuronal activation, we have scanned the somatosensory cortex of awake rabbits during whisker stimulation, while simultaneously recording somatosensory cortical action potentials and field oscillations. Functional MR imaging experiments were performed on a 4.7T Bruker BioSpec imaging spectrometer operating at 200.3 MHz for 1H frequency. A single-turn, 40-mm diameter radiofrequency surface coil was used for both transmission and reception. Imaging data were acquired from four consecutive, 1mm-thick slices in transverse plane using a single-shot gradient-echo EPI pulse sequence with the following parameters: FOV=48mm x 48mm, image matrix=80 x 64, TR=2s and TE=20ms. All responses were detected using cross correlation, on a pixel-by-pixel basis, with a box function representing whisker stimulation timing. Neuronal activity was recorded through 100 μm PtIr electrodes chronically implanted into whisker cortex. Activity was amplified and d...

The degree to which visual processing within ventral extrastriate brain regions, including the fusiform gyrus, is domain specific is a contentious issue. Part of the controversy may stem from the differing nature of the measures used to investigate this issue. Functional MRI measures hemodynamic changes that evolve over seconds and involve venous elements that may overestimate the spatial extent of neural activation. Direct electrical recording through subdural electrode strips and grids provide an alternative measure of neural activity with high spatial and temporal resolution. Here we will discuss two experiments that used identical presentations of visual stimuli comprising many object categories including faces. Direct electrical recordings in a sample of patients undergoing intracranial investigation for epilepsy were compared to fMRI responses evoked by the same stimuli in controls. In the present studies, we presented a series of objects from several categories and faces. Interspersed within this se...

Untreated hypertension causes many vascular abnormalities such as thickening of the tunica media and luminal dilation in a response to increased flow. Aging may lead to alterations in the blood-brain barrier (BBB) and changes in the white matter. The co-morbidity of hypertension with age complicates identification of their independent contribution to age-related changes in the cerebrovascular system. To isolate the roles of hypertension and age we developed a non-human primate model of hypertensive cerebrovascular disease in which the thoracic aorta is surgically coarcted to 2.5 mm to induce sustained hypertension (systolic 150-185 mmHg). Rhesus monkeys were divided into four groups, young (5-8 yrs) and middle aged (15-20 yrs) normotensive and young and middle aged hypertensive. Two years after entry into the study, T1 weighted serial MR images were acquired on each monkey prior to and following injection of Magnevist (gadopentate dimeglumine), a contrast agent that normally doesn’t cross the BBB. Images w...

Previous research in humans has explored the relationship between volumetric measurements of the hippocampus and amygdala, the degree of volumetric asymmetry of these structures, and various cognitive and psychiatric symptoms. The present study provides the first systematic analysis using meta-analytic procedures of the normal population parameters of hippocampal and amygdala volumetric asymmetry as well as absolute intrahemispheric volumes in healthy adult individuals. A literature review resulted in a representative sample of 62 studies (N = 2,364 participants) providing volumetric information for the left and right hippocampi and 38 studies (N = 1,569 participants) providing volumetric information for the left and right amygdala. Results revealed that, in humans, the hippocampus is a statistically reliable asymmetrical structure in normal adults, with a relative larger right hemisphere volume (effect size Dh = 0.19, p < 0.001). The amygdala, however, was not found to be reliably asymmetrical. Additional...

Lipopolysaccharide (LPS), a potent endotoxin, derived from the cell wall of gram-negative bacteria causes severe inflammation in the brain. Neuroinflammation is associated with several neurodegenerative diseases, including stroke, Parkinson’s disease, Alzheimer’s disease, multiple sclerosis and amyotrophic lateral sclerosis. The hallmark of brain inflammation is the activation of microglial cells that produce proinflammatory and neurotoxic factors, including cytokines and free radicals. In the present study we correlate magnetic resonance imaging (MRI) and immunohistochemistry applying different neuronal and glial markers to analyse neurodegenerative processes in a LPS-mediated model of neuroinflammation. As demonstrated by MRI, unilateral injection of LPS into the striatum of rats led to structural changes at different time points following endotoxin application. In parallel, immunfluorescence with Fluoro-Jade B showed an increased number of degenerating neurons in the striatum 24 hours, 3 and 7 days afte...