Explore the vast range of titles available.

Structural magnetic resonance imaging can now resolve laminar features within the cerebral cortex in vivo. A variety of intracortical contrasts have been used to study the cortical myeloarchitecture with the purpose of mapping cortical areas in individual subjects. In this article, we first briefly review recent advances in MRI analysis of cortical microstructure to portray the potential and limitations of the current state-of-the-art. We then present an integrated framework for the analysis of intracortical structure, composed of novel image processing tools designed for high resolution cortical images. The main features of our framework are the segmentation of quantitative T1 maps to delineate the cortical boundaries (Bazin et al., 2014), and the use of an equivolume layering model to define an intracortical coordinate system that follows the anatomical layers of the cortex (Waehnert et al., 2014). We evaluate the framework with 150μm isotropic post mortem T2∗-weighted images and 0.5mm isotropic in vivo T1 maps, a quantitative index of myelin content. We study the laminar structure of the primary visual cortex (Brodmann area 17) in the post mortem and in vivo data, as well as the central sulcus region in vivo, in particular Brodmann areas 1, 3b and 4. We also investigate the impact of the layering models on the relationship between T1 and cortical curvature. Our experiments demonstrate that the equivolume intracortical surfaces and transcortical profiles best reflect the laminar structure of the cortex in areas of curvature in comparison to the state-of-the-art equidistant and Laplace implementations. This framework generates a subject specific intracortical coordinate system, the basis for subsequent architectonic analyses of the cortex. Any structural or functional contrast co-registered to the T1 maps, used to segment the cortex, can be sampled on the curved grid for analysis. This work represents an important step towards in vivo structural brain mapping of individual subjects. •The framework includes segmentation of T1 maps and equivolume cortical layering.•All processing is performed at high resolution, 0.4mm isotropic.•A native curved 3D intracortical coordinate system is defined to sample MRI data.•The computed T1 cortical profiles accurately reflect cortical myeloarchitecture.

•χ-separation, a magnetic susceptibility source separation method, is applied to explore iron and myelin profiles across layers of cortex and white matter.•The depth-wise profiles of χpos and χneg were consistent with the profiles of iron and myelin from literatures.•The depth-wise profiles of χpos and χneg were different from those of QSM or R2*, carrying different information. The in-vivo profiling of iron and myelin across cortical depths and underlying white matter has important implications for advancing knowledge about their roles in brain development and degeneration. Here, we utilize χ-separation, a recently-proposed advanced susceptibility mapping that creates positive (χpos) and negative (χneg) susceptibility maps, to generate the depth-wise profiles of χpos and χneg as surrogate biomarkers for iron and myelin, respectively. Two regional sulcal fundi of precentral and middle frontal areas are profiled and compared with findings from previous studies. The results show that the χpos profiles peak at superificial white matter (SWM), which is an area beneath cortical gray matter known to have the highest accumulation of iron within the cortex and white matter. On the other hand, the χneg profiles increase in SWM toward deeper white matter. These characteristics in the two profiles are in agreement with histological findings of iron and myelin. Furthermore, the χneg profiles report regional differences that agree with well-known distributions of myelin concentration. When the two profiles are compared with those of QSM and R2*, different shapes and peak locations are observed. This preliminary study offers an insight into one of the possible applications of χ-separation for exploring microstructural information of the human brain, as well as clinical applications in monitoring changes of iron and myelin in related diseases.

Cortical layer-dependent high (sub-millimeter) resolution functional magnetic resonance imaging (fMRI) in human or animal brain can be used to address questions regarding the functioning of cortical circuits, such as the effect of different afferent and efferent connectivities on activity in specific cortical layers. The sensitivity of gradient echo (GE) blood oxygenation level-dependent (BOLD) responses to large draining veins reduces its local specificity and can render the interpretation of the underlying laminar neural activity impossible. The application of the more spatially specific cerebral blood volume (CBV)-based fMRI in humans has been hindered by the low sensitivity of the noninvasive modalities available. Here, a vascular space occupancy (VASO) variant, adapted for use at high field, is further optimized to capture layer-dependent activity changes in human motor cortex at sub-millimeter resolution. Acquired activation maps and cortical profiles show that the VASO signal peaks in gray matter at 0.8–1.6mm depth, and deeper compared to the superficial and vein-dominated GE-BOLD responses. Validation of the VASO signal change versus well-established iron-oxide contrast agent based fMRI methods in animals showed the same cortical profiles of CBV change, after normalization for lamina-dependent baseline CBV. In order to evaluate its potential of revealing small lamina-dependent signal differences due to modulations of the input-output characteristics, layer-dependent VASO responses were investigated in the ipsilateral hemisphere during unilateral finger tapping. Positive activation in ipsilateral primary motor cortex and negative activation in ipsilateral primary sensory cortex were observed. This feature is only visible in high-resolution fMRI where opposing sides of a sulcus can be investigated independently because of a lack of partial volume effects. Based on the results presented here, we conclude that VASO offers good reproducibility, high sensitivity and lower sensitivity than GE-BOLD to changes in larger vessels, making it a valuable tool for layer-dependent fMRI studies in humans. [Display omitted] •A CBV-sensitive fMRI method is developed for high-resolution fMRI in humans.•Lamina-dependent CBV fMRI responses are shown in humans.•VASO cortical profiles are validated with Fe-contrast agent fMRI in animals.•Sensitivity to large veins can be minimized using VASO-CBV instead of BOLD fMRI.•Ipsilateral fMRI responses to finger tapping are positive in M1 and negative in S1.

This work presents a novel approach for modelling laminar myelin patterns in the human cortex in brain MR images on the basis of known cytoarchitecture. For the first time, it is possible to estimate intracortical contrast visible in quantitative ultra-high resolution MR images in specific primary and secondary cytoarchitectonic areas. The presented technique reveals different area-specific signatures which may help to study the spatial distribution of cortical T1 values and the distribution of cortical myelin in general. It may lead to a new discussion on the concordance of cyto- and myeloarchitectonic boundaries, given the absence of such concordance atlases. The modelled myelin patterns are quantitatively compared with data from human ultra-high resolution in-vivo 7T brain MR images (9 subjects). In the validation, the results are compared to one post-mortem brain sample and its ex-vivo MRI and histological data. Details of the analysis pipeline are provided. In the context of the increasing interest in advanced methods in brain segmentation and cortical architectural studies, the presented model helps to bridge the gap between the microanatomy revealed by classical histology and the macroanatomy visible in MRI. •We present a model that predicts T1 contrast related to myelin as measured with MRI.•The predictions are based on cytoarchitectural a-priori information.•When compared to in-vivo T1 maps the model reveals area-specific signatures.•Quantitative analysis shows agreement between in-vivo T1 maps and model.•Visual comparison to classical histology data is provided.

Studies into cortical thickness in psychiatric diseases based on T1-weighted MRI frequently report on aberrations in the cerebral cortex. Due to limitations in image resolution for studies conducted at conventional MRI field strengths (e.g. 3 Tesla (T)) this information cannot be used to establish which of the cortical layers may be implicated. Here we propose a new analysis method that computes one high-resolution average cortical profile per brain region extracting myeloarchitectural information from T1-weighted MRI scans that are routinely acquired at a conventional field strength. To assess this new method, we acquired standard T1-weighted scans at 3 T and compared them with state-of-the-art ultra-high resolution T1-weighted scans optimised for intracortical myelin contrast acquired at 7 T. Average cortical profiles were computed for seven different brain regions. Besides a qualitative comparison between the 3 T scans, 7 T scans, and results from literature, we tested if the results from dynamic time warping-based clustering are similar for the cortical profiles computed from 7 T and 3 T data. In addition, we quantitatively compared cortical profiles computed for V1, V2 and V7 for both 7 T and 3 T data using a priori information on their relative myelin concentration. Although qualitative comparisons show that at an individual level average profiles computed for 7 T have more pronounced features than 3 T profiles the results from the quantitative analyses suggest that average cortical profiles computed from T1-weighted scans acquired at 3 T indeed contain myeloarchitectural information similar to profiles computed from the scans acquired at 7 T. The proposed method therefore provides a step forward to study cortical myeloarchitecture in vivo at conventional magnetic field strength both in health and disease.

Improvements in the spatial resolution of structural and functional MRI are beginning to enable analysis of intracortical structures such as heavily myelinated layers in 3D, a prerequisite for in-vivo parcellation of individual human brains. This parcellation can only be performed precisely if the profiles used in cortical analysis are anatomically meaningful. Profiles are often constructed as traverses that are perpendicular to computed laminae. In this case they are fully determined by these laminae. The aim of this study is to evaluate models for cortical laminae used so far and to establish a new model. Methods to model the laminae used so far include constructing laminae that keep a constant distance to the cortical boundaries, so-called equidistant laminae. Another way is to compute equipotentials between the cortical boundary surfaces with the Laplace equation. The Laplace profiles resulting from the gradients to the equipotentials were often-used because of their nice mathematical properties. However, the equipotentials these Laplacian profiles are constructed from and the equidistant laminae do not follow the anatomical layers observed using high resolution MRI of cadaver brain. To remedy this problem, we introduce a novel equi-volume model that derives from work by Bok (1929). He argued that cortical segments preserve their volume, while layer thickness changes to compensate cortical folding. We incorporate this preservation of volume in our new equi-volume model to generate a three-dimensional well-adapted undistorted coordinate system of the cortex. When defined by this well-adapted coordinate system, cortical depth is anatomically meaningful. We compare isocontours from these cortical depth values to locations of myelinated bands on high-resolution ex-vivo and in-vivo three-dimensional MR images. A similar comparison was performed with equipotentials computed with the Laplace equation and with equidistant isocontours. A quantitative evaluation of the equi-volume model using measured image intensities confirms that it provides a much better fit to observed cortical layering. •Cortical profiles are needed for cortical thickness measurements and parcellation.•Laplace equipotentials do not follow the anatomical layers observed with MRI.•Our model preserves volume and changes layer thickness to compensate folding.•We compare Laplace and equi-volume laminae with myelinated bands ex- and in-vivo.•The novel equi-volume model fits observed cortical stratification much better.

Purpose Although premature birth is recognised as a cause of cerebral visual impairment (CVI), which can include cerebral visual dysfunction (CVD), the incidence and nature of CVD in prematurely born children is not known. Methods A prospective, controlled investigation was undertaken of forty-six, mainstream primary school children, prematurely born with gestations of 24.0–34.6 weeks, and of 130 control (term-born) children. Assessments were made of IQ, ophthalmic functions, visual perception and visual attention. Structured history-taking seeking evidence of behavioural features of CVI used a question inventory. Obstetric, neonatal and paediatric medical histories were documented from case records. Results Fifteen out of forty-six (33 %) of the prematurely born children—“cluster A”—revealed behaviours corresponding with CVD on cluster analysis of the CVI inventory. The whole prematurely born group performed worse than controls on all visual perception tests and all four visual attention tests. Children in cluster A were responsible for this effect, performing worse than controls on all visual perception and visual attention tests except visual closure, while cluster B prematurely born children performed no differently to controls. Conclusions The prevalence of CVD in these prematurely born children is between 21–47 % (95 % CI), with a pattern similar to “dorsal stream dysfunction”. Currently available perceptual tests appear to be unable to identify the specific pattern of problems noted in this group. Many studies have provided evidence of cognitive and intellectual dysfunction in prematurely born children, and it is possible that CVD is a contributor. The CVI inventory is a potential means of identifying and characterising the condition, which can be ameliorated with simple strategies.

Background Schizophrenia (SCZ) is marked by profound biological and clinical heterogeneity, presenting major challenges for accurate diagnosis and personalized treatment. Traditional classifications based solely on clinical presentation are limited by inter-individual variability, overlapping symptom profiles, and low stability across disease stages and treatment states. Dysregulation of the excitation–inhibition (E–I) balance within neural circuits is thought to underpin diverse positive and negative symptoms. Classification based on neural excitability may therefore provide critical insights into disentangling this heterogeneity. Methods We applied a cortical excitability (CE) mapping approach to spatially characterize E–I dysregulations in 77 drug-naïve first-episode SCZ (FES) patients and 76 healthy controls (HCs). CE abnormalities were identified using voxel-wise comparisons, and patients were subsequently clustered into subtypes based on the spatial patterns of CE alterations. Longitudinal analyses assessed the subgroups’ clinical trajectories over 12 months of antipsychotic treatment. Furthermore, CE maps were integrated with transcriptomic and neuroreceptor datasets to analyse potential molecular mechanisms underlying the observed CE abnormalities. Results Relative to HCs, FES patients exhibited CE abnormalities primarily in the bilateral frontal lobes, sensorimotor cortex, and right cuneus. Two subtypes were identified, differing in both the spatial extent of CE abnormalities and their clinical profiles: FES1 showed more widespread CE reductions across frontal and association cortices, associated with greater affective and cognitive burden, whereas FES2 demonstrated a comparatively preserved CE profile and milder symptom expression. Subsequent transcriptomic and receptor analyses revealed distinct biological underpinnings: FES1 was associated with synaptic dysfunction and neurodevelopmental disruption, while FES2 reflected multisystem involvement potentially accompanied by compensatory processes. Conclusions CE-based subtyping captures clinically and biologically meaningful heterogeneity in FES. Moreover, this approach provides a promising framework for bridging neural circuit dysfunction with molecular signatures and may advance precision psychiatry in SCZ.

The newly established mouse cortical-bone-derived stem cells (mCBSCs) are unique stem cells compared to mouse mesenchymal stem cells (mMSCs). The mCBSC-treated hearts after myocardial infarction have been reported to have greater improvement in myocardial structure and functions. In this study, we examined the stemness features, cell surface glycan profiles, and paracrine functions of mCBSCs compared with mMSCs. The stemness analysis revealed that the self-renewing capacity of mCBSCs was greater than mMSCs; however, the differentiation capacity of mCBSCs was limited to the chondrogenic lineage among three types of cells (adipocyte, osteoblast, chondrocyte). The cell surface glycan profiles by lectin array analysis revealed that α2-6sialic acid is expressed at very low levels on the cell surface of mCBSCs compared with that on mMSCs. In contrast, the lactosamine (Galβ1-4GlcNAc) structure, poly lactosamine- or poly N-acetylglucosamine structure, and α2-3sialic acid on both N- and O-glycans were more highly expressed in mCBSCs. Moreover, we found that mCBSCs secrete a greater amount of TGF-β1 compared to mMSCs, and that the TGF-β1 contributed to the self-migration of mCBSCs and activation of fibroblasts. Together, these results suggest that unique characteristics in mCBSCs compared to mMSCs may lead to advanced utility of mCBSCs for cardiac and noncardiac repair.

Low‐profile topping‐off surgery, combining cortical bone trajectory screws with pedicle screws and Coflex stabilization, achieved comparable clinical outcomes to traditional topping‐off, with reduced incision length, blood loss, and drainage. This technique offers a less invasive approach and faster recovery for patients with lumbar degenerative diseases.