Cortical reorganization occurring in multiple sclerosis (MS) patients is thought to play a key role in limiting the effect of structural tissue damage. Conversely, its exhaustion may contribute to the irreversible disability that accumulates with disease progression. Several aspects of MS-related cortical reorganization, including the overall functional effect and likely modulation by therapies, still remain to be elucidated. The aim of this work was to assess the extent of functional cortical reorganization and its brain structural/pathological correlates in Dark Agouti rats with experimental autoimmune encephalomyelitis (EAE), a widely accepted preclinical model of chronic MS. Morphological and functional MRI (fMRI) were performed before disease induction and during the relapsing and chronic phases of EAE. During somatosensory stimulation of the right forepaw, fMRI demonstrated that cortical reorganization occurs in both relapsing and chronic phases of EAE with increased activated volume and decreased la...

In macaque monkeys, dorsal intraparietal areas are involved in several daily visuomotor actions. However, their border and sources of cortical afferents remain loosely defined. Combining retrograde histologic tracing and MRI diffusion-based tractography, we found a complex hodology of the dorsal bank of the intraparietal sulcus (db-IPS), which can be subdivided into a rostral intraparietal area PEip, projecting to the spinal cord, and a caudal medial intraparietal area MIP lacking such projections. Both include an anterior and a posterior sector, emerging from their ipsilateral, gradient-like connectivity profiles. As tractography estimations, we used the cross-sectional area of the white matter bundles connecting each area with other parietal and frontal regions, after selecting regions of interest (ROIs) corresponding to the injection sites of neural tracers. For most connections, we found a significant correlation between the proportions of cells projecting to all sectors of PEip and MIP along the conti...

To determine the extent of spinal cord injury over time in rats, we are using noninvasive techniques, including conventional MRI and diffusion-weighted MRI, to evaluate the integrity of the spinal cord, the volume of injury and inflammatory changes. Adult female Sprague-Dawley rats were injured at the T9 level using the NYU impactor (10 g from 50mm on to the intact spinal cord). Locomotor behavior was recorded weekly using BBB score. At the end of 2, 7, 14 and 28 days non-fixed spinal columns were placed into a 10mm bore glass tube for MRI analysis using a 7 Tesla vertical bore magnet with the Bruker Biospin®10mm MICRO imaging probe and ParaVision 3.0.2® image acquisition software. Seven 1mm thick coronal and sagittal slices and twenty-three 1mm thick axial slice images were captured to show the entire region of interest in the spinal cord. The in-plane image resolution of the coronal and sagittal slices was 39µm/pixel and in the axial slices was 43µm/pixel. Multi-slice spin echo images at TR = 2100ms, TE ...

This anatomical study presents MRI-based volumetric analysis of all structures of the Medial Temporal Lobe (MTL) including the hippocampus, the amygdala, the temporopolar cortex and the parahippocampal gyrus (perirhinal, entorhinal and parahippocampal cortices) spared after unilateral MTL removal carried out for the treatment of drug-refractory temporal-lobe epilepsy. Such methods already applied to epileptic patients before surgery, have not been used after surgical treatment. Based on the location of the remaining anatomical landmarks, we quantified the volume of all these regions in 40 patients after unilateral MTL resection (right: N= 20; left: N = 20) and in 16 control participants using MRI-based volumetric analysis. The results showed that (1) the mean volumes of these regions contralateral to the epileptic focus were similar to those measured from normal subjects (2) the volumetric measures obtained from the resected side were obviously reduced compared to those from the non-resected side or from n...

Epochal developmental events like pregnancy and lactation can alter cortical organization and representation affecting memory, perception and attendant behavior. This study used fMRI to observe cortical activation in conscious, first time mother (primiparous) rats in response to pup suckling vs the general tactile stimulus of mechanical rubbing. Pup suckling and general tactile stimulation over the long hair of the ventrum and hairless skin of the nipples and areolas resulted in a similar pattern of cortical activation in primiparous dams. Ventrum rubbing in virgin females activated the same cortical areas. In addition to the anticipated stimulus-evoked activity in the somatosensory cortex, activation was observed in parietal, motor, temporal, cingulate, retrosplenial, auditory and visual cortices for all stimulus conditions. These activations suggest that the stimuli under these experimental conditions were not modality specific and promoted general arousal across the cortical mantel. Interestingly, the s...

Hippocampal volumetrics are important for studying disease progression and diagnosis of temporal lobe epilepsy, Alzheimer’s disease and schizophrenia. However, comparing volumetric variation across studies is difficult due to differing anatomical boundaries, subject characteristics, statistical analyses and image processing techniques. One approach to this problem is to create a database of the homogeneous aspects of studies to increase uniformity and get comparative results. The Internet Brain Volume Database (IBVD) was created to provide a comparison of the various aspects of volumetric studies. As an example of this approach, the current study evaluates normal ranges of volumes in the hippocampus across published studies with similar manual methods and anatomical boundaries. The purpose was to compare and evaluate region of interest (ROI) methods of volumetric analysis and generate a summary of trends and results. Twenty-two peer-reviewed studies involving ROI measurements of the hippocampus were survey...

The stria of Gennari --a definitive landmark for anatomical identification of primary visual cortex--has been imaged both ex vivo and in vivo and visualized in planar sections, but no surface reconstructions were performed. To image the stria, we used a high-bandwidth, multiecho FLASH pulse sequence with an isotropic voxel size of 200 microns and scanned ex vivo human occipital cortex at 7T for 12 hours. This provided enhanced contrast between gray and white matter and reduced MR image distortion, thus enabling reliable identification of the full extent of the stria. We developed software for reconstructing surfaces from slice images obtained either from MRI or serial tissue section data. This software was used to identify vertices representing points of the stria as input to a surface tiling algorithm, which outputs a two-dimensional, manifold triangular mesh representing the striate surface. A flattened surface was obtained using an accurate quasi-isometric flattening algorithm (see Balasubramanian et al...

The goal of this study was to use functional imaging to examine cortical plasticity and to identify neuronal activity changes in the network level after peripheral nerve injury. High resolution functional Magnetic Resonance Imaging (fMRI) has emerged as an important tool to study brain plasticity in humans and rodents in a non-invasive manner. In order to detect cortical reorganization, we have applied the common sciatic and the saphenous (the main nerves innervating the hindlimb) nerves injury model in rats, which was previously shown to induce short- as well as long-term intra-cortical plasticity changes at the cellular and at the network level. At different time points after surgery, fMRI was performed on an 11.7T animal MRI system on sham-operated rats, on sciatic nerve cut rats, and on rats where both the sciatic and saphenous nerves were cut. Electrical stimulation of the healthy hindlimb in the sham-operated and in the sciatic nerve cut rat groups resulted in normal contra-lateral somatosensory cort...

Memories vary in their durability even when encoding conditions apparently remain constant. We investigated whether, under these circumstances, memory durability is nonetheless associated with variation in the neural activity elicited during encoding. Event-related functional magnetic resonance imaging data were acquired while volunteers semantically classified visually presented words. Using the “remember/know” procedure, memory for one-half of the words was tested after 30 min and for the remaining half after 48 h. In several regions, including left hippocampus and left dorsal inferior frontal gyrus (IFG), activity at encoding differed depending on whether items were later recollected regardless of study-test delay. Delay-selective effects were also evident, however. Recollection after 48 h was associated with enhanced activity in bilateral ventral IFG, whereas recollection after 30 min was associated with greater fusiform activity. Thus, there is a relationship between the neural activity elicited by an...

In macaque monkeys, dorsal intraparietal areas are involved in several daily visuo-motor actions. However, their border and sources of cortical afferents remain loosely defined. Combining retrograde histological tracing and MRI diffusion-based tractography we found a complex hodology of the dorsal bank of the IPS, which can be subdivided into a rostral area PEip, projecting to the spinal cord, and a caudal area MIP lacking such projections. Both include a rostral and a caudal sector, emerging from their ipsilateral, gradient-like connectivity profiles. As tractography estimations, we used the cross-sectional volume of the white matter bundles connecting each area with other parietal and frontal regions, after selecting ROIs corresponding to the injection sites of neural tracers. For most connections, we found a significant correlation between the proportions of cells projecting to all sectors of PEip and MIP along the continuum of the dorsal bank of the IPS and tractography. The latter also revealed “false...