Investigating Intra-Individual Networks of Response Inhibition and Interference Resolution using 7T MRI.

Response inhibition and interference resolution are often considered subcomponents of an overarching inhibition system that utilizes the so-called cortico-basal-ganglia loop. Up until now, most previous functional magnetic resonance imaging (fMRI) literature has compared the two using between-subject designs, pooling data in the form of a meta-analysis or comparing different groups. Here, we investigate the overlap of activation patterns underlying response inhibition and interference resolution on a within-subject level, using ultra-high field MRI. In this model-based study, we furthered the functional analysis with cognitive modelling techniques to provide a more in-depth understanding of behaviour. We applied the stop-signal task and multi-source interference task to measure response inhibition and interference resolution, respectively. Our results lead us to conclude that these constructs are rooted in anatomically distinct brain areas and provide little evidence for spatial overlap. Across the two tasks, common BOLD responses were observed in the inferior frontal gyrus and anterior insula. Interference resolution relied more heavily on subcortical components, specifically nodes of the commonly referred to indirect and hyperdirect pathways, as well as the anterior cingulate cortex, and pre-supplementary motor area. Our data indicated that orbitofrontal cortex activation is specific to response inhibition. Our model-based approach provided evidence for the dissimilarity in behavioural dynamics between the two tasks. The current work exemplifies the importance of reducing inter-individual variance when comparing network patterns and the value of UHF-MRI for high resolution functional mapping.

Human Cerebellar Sub-millimeter Diffusion Imaging Reveals the Motor and Non-motor Topography of the Dentate Nucleus.

The reciprocal cortico-cerebellar loops that underlie cerebellar contributions to motor and cognitive behavior form one of the largest systems in the primate brain. Work with non-human primates has shown that the dentate nucleus, the major output nucleus of the cerebellum, contains topographically distinct connections to both motor and non-motor regions, yet there is no evidence for how the cerebellar cortex connects to the dentate nuclei in humans. Here we used in-vivo sub-millimeter diffusion imaging to characterize this fundamental component of the cortico-cerebellar loop, and identified a pattern of superior motor and infero-lateral non-motor connectivity strikingly similar to that proposed by animal work. Crucially, we also present first evidence that the dominance for motor connectivity observed in non-human primates may be significantly reduced in man - a finding that is in accordance with the proposed increase in cerebellar contributions to higher cognitive behavior over the course of primate evolution.

Metal-organic and covalent organic frameworks as single-site catalysts.

Heterogeneous single-site catalysts consist of isolated, well-defined, active sites that are spatially separated in a given solid and, ideally, structurally identical. In this review, the potential of metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) as platforms for the development of heterogeneous single-site catalysts is reviewed thoroughly. In the first part of this article, synthetic strategies and progress in the implementation of such sites in these two classes of materials are discussed. Because these solids are excellent playgrounds to allow a better understanding of catalytic functions, we highlight the most important recent advances in the modelling and spectroscopic characterization of single-site catalysts based on these materials. Finally, we discuss the potential of MOFs as materials in which several single-site catalytic functions can be combined within one framework along with their potential as powerful enzyme-mimicking materials. The review is wrapped up with our personal vision on future research directions.

Investigation of the confounding effects of vasculature and metabolism on computational anatomy studies.

Computational anatomy studies typically use T1-weighted magnetic resonance imaging contrast to look at local differences in cortical thickness or grey matter volume across time or subjects. This type of analysis is a powerful and non-invasive tool to probe anatomical changes associated with neurodevelopment, aging, disease or experience-induced plasticity. However, these comparisons could suffer from biases arising from vascular and metabolic subject- or time-dependent differences. Differences in blood flow and volume could be caused by vasodilation or differences in vascular density, and result in a larger signal contribution of the blood compartment within grey matter voxels. Metabolic changes could lead to differences in dissolved oxygen in brain tissue, leading to T1 shortening. Here, we analyze T1 maps and T1-weighted images acquired during different breathing conditions (ambient air, hypercapnia (increased CO2) and hyperoxia (increased O2)) to evaluate the effect size that can be expected from changes in blood flow, volume and dissolved O2 concentration in computational anatomy studies. Results show that increased blood volume from vasodilation during hypercapnia is associated with an overestimation of cortical thickness (1.85%) and grey matter volume (3.32%), and that both changes in O2 concentration and blood volume lead to changes in the T1 value of tissue. These results should be taken into consideration when interpreting existing morphometry studies and in future study design. Furthermore, this study highlights the overlap in structural and physiological MRI, which are conventionally interpreted as two independent modalities.

A cytoarchitecture-driven myelin model reveals area-specific signatures in human primary and secondary areas using ultra-high resolution in-vivo brain MRI.

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.

Prospective slice-by-slice motion correction reduces false positive activations in fMRI with task-correlated motion.

OBJECTIVE: We aimed to test the hypothesis that slice-by-slice prospective motion correction at 7T using an optical tracking system reduces the rate of false positive activations in an fMRI group study with a paradigm that involves task-correlated motion. MATERIALS AND METHODS: Brain activation during right leg movement was measured using a block design on 15 volunteers, with and without prospective motion correction. Clearly erroneous activations were compared between both cases, at the individual level. Additionally, conventional group analysis was performed. RESULTS: The number of falsely activated voxels with T-values higher than 5 was reduced by 48% using prospective motion correction alone, without additional retrospective realignment. In the group analysis, the statistical power was increased - the peak T-value was 26% greater, and the number of voxels in the cluster representing the right leg was increased by a factor of 9.3. CONCLUSION: Slice-by-slice prospective motion correction in fMRI studies with task-correlated motion can substantially reduce false positive activations and increase statistical power.

Anatomically motivated modeling of cortical laminae.

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.

Quantifying inter-individual anatomical variability in the subcortex using 7 T structural MRI.

Functional magnetic resonance imaging (MRI) data are usually registered into standard anatomical space. However, standard atlases, such as LPBA40, the Harvard-Oxford atlas, FreeSurfer, and the Jülich cytoarchitectonic maps all lack important detailed information about small subcortical structures like the substantia nigra and subthalamic nucleus. Here we introduce a new subcortical probabilistic atlas based on ultra-high resolution in-vivo anatomical imaging from 7 T MRI. The atlas includes six important but elusive subcortical nuclei: the striatum, the globus pallidus internal and external segment (GPi/e), the subthalamic nucleus, the substantia nigra, and the red nucleus. With a sample of 30 young subjects and carefully cross-validated delineation protocols, our atlas is able to capture the anatomical variability within healthy populations for each of the included structures at an unprecedented level of detail. All the generated probabilistic atlases are registered to MNI standard space and are publicly available.

Cortical and subcortical contributions to interference resolution and inhibition - An fMRI ALE meta-analysis.

Interacting with our environment requires the selection of appropriate responses and the inhibition of others. Such effortful inhibition is achieved by a number of interference resolution and global inhibition processes. This meta-analysis including 57 studies and 73 contrasts revisits the overlap and differences in brain areas supporting interference resolution and global inhibition in cortical and subcortical brain areas. Activation likelihood estimation was used to discern the brain regions subserving each type of cognitive control. Individual contrast analysis revealed a common activation of the bilateral insula and supplementary motor areas. Subtraction analyses demonstrated the voxel-wise differences in recruitment in a number of areas including the precuneus in the interference tasks and the frontal pole and dorsal striatum in the inhibition tasks. Our results display a surprising lack of subcortical involvement within these types of cognitive control, a finding that is likely to reflect a systematic gap in the field of functional neuroimaging.

Effects of aging on T1, T2*, and QSM MRI values in the subcortex.

The aging brain undergoes several anatomical changes that can be measured with Magnetic Resonance Imaging (MRI). Early studies using lower field strengths have assessed changes in tissue properties mainly qualitatively, using [Formula: see text]- or [Formula: see text]- weighted images to provide image contrast. With the development of higher field strengths (7 T and above) and more advanced MRI contrasts, quantitative measures can be acquired even of small subcortical structures. This study investigates volumetric, spatial, and quantitative MRI parameter changes associated with healthy aging in a range of subcortical nuclei, including the basal ganglia, red nucleus, and the periaqueductal grey. The results show that aging has a heterogenous effects across regions. Across the subcortical areas an increase of [Formula: see text] values is observed, most likely indicating a loss of myelin. Only for a number of areas, a decrease of [Formula: see text] and increase of QSM is found, indicating an increase of iron. Aging also results in a location shift for a number of structures indicating the need for visualization of the anatomy of individual brains.

[Radiofrequency ablation of atrioventricular conduction during the 5th month of pregnancy]. / Interruption de la conduction auriculo-ventriculaire par radiofréquence au 5e mois d'une grossesse.

The authors report the case of radiofrequency ablation of atrioventricular conduction in a 5 months pregnant woman who had hypertrophic cardiomyopathy. The indication of this procedure was a poorly tolerated resistant supraventricular tachycardia with foetal distress. A dual-chamber rate-assisted pacemaker programmed in the VVIR mode was implanted during the same procedure normally, with normal delivery of a healthy child at 8 months' gestation.

[Long-term outcome of a hospital series of patients with atrio-ventricular accessory pathway]. / Devenir à long terme d'une série hospitalière de patients ayant une voie de conduction accessoire auriculo-ventriculaire.

Ninety five patients with a mean age of 39 +/- 19 years, 82 of whom were symptomatic, having an accessory atrioventricular bidirectional conduction pathway (WPW syndrome: 77; "concealed": 18) were followed up for an average of 7.3 +/- 2.6 years. The objectives were to analyse: the incidence and causes of death and the possible predictive factors of death due to the WPW syndrome--the influence of medical treatment and type of medication on survival and symptoms. Of the 8 cardiac deaths, 6 seemed to be related to the WPW syndrome, a prevalence of 7.8% and an annual incidence of 1.1/1000. The main risk factors which were identified were: age 62 +/- 8 years versus 37 +/- 15 years in survivors; p < 0.02--associated organic heart disease, especially ischaemic heart disease (5/6)--the description of severe symptoms, in particular recurrent syncope--documented malignant spontaneous or induced arrhythmias (5/6)--anterograde AV conduction with an effective refractory period < or = 230 msec in 4, though it was only 270 msec in the other 2 patients, indicating that this parameter is not specific--amiodarone (6/6) did not prevent the fatal outcome in this particular group of patients. In the "benign" forms, only betablocker drugs could significantly reduce the frequency and severity of symptoms, especially when compared with Class I or IC antiarrhythmics. These results suggest that the indications of radical treatment should be widened in high risk patients, especially when elderly and with associated coronary artery disease. They also suggest that the role of betablocker drugs should be reevaluated in the so-called "benign" symptomatic forms.

[Myocardial pseudo-infarction: "stress"-associated catecholamine-induced acute cardiomyopathy or coronary spasm?]. / Tableau de pseudo-infarctus du myocarde: cardiomyopathie catécholergique aiguë "de stress" ou spasme coronarien?

As well as pheochromocytoma, in which it has been established that an excess of circulating catecholamines is responsible for the development of catecholamine-induced acute myopathy, some rare cases have been reported of a similar cardiac incident following intense emotional stress. In this study, the case has been examined of a 56-year old female with no history of cardiovascular disorder who presented with intense, nitro-resistant prolonged chest pain mimicking an acute coronary syndrome immediately following a situation involving major psychological stress. The admission electrocardiogram revealed a sharp decrease in R-wave amplitude in the right chest leads associated with an extended QT interval, and secondarily with subepicardiac ischemia in the lower leads. However, a few days after admission the electrical signs and septo-apical akinesia that had initially been observed by echocardiography completely disappeared. The clinical examination ruled out a diagnosis of myocardial necrosis, acute myocarditis, or pheochromocytoma. Moreover, no direct evidence of coronary spasm was found. The outcome was positive, with complete reversibility of all clinical signs and no organic sequelae. It is considered that this was probably a case of catecholaminergic acute cardiomyopathy triggered by intense emotional stress, a rare occurrence that should nevertheless be systematically taken into account in cases with similar clinical signs.

[Is it possible to propose the abolition of crutches according to the gait speed in patients with total knee arthroplasty?]. / Peut-on proposer la suppression des cannes anglaises en fonction de la vitesse de marche chez les patients porteurs d'une prothèse totale de genou ?

OBJECTIVE: To determine the stop of crutches to walk in patients with total knee arthroplasty from the test of maximal gait speed. METHOD: 46 patients (73.6 +/- 4.6 years) carried out the maximal gait speed test on a 10-meter track, with two crutches, at the 3rd week after a total knee arthroplasty surgery for gonarthrosis. Two groups were separated according to the need of crutches to walk. Various threshold values of maximal gait speed were then determined (ROC curve) to know if this parameter could define the stop of crutches to walk (Predictive value). RESULTS: Patients able to stop crutches (n = 27) walk faster, than the patients who still need crutches (n = 19), (0.86 +/- 0.17 m/s vs 0.65 +/- 0.14 m/s; p < 0.01). According to the ROC curve, two speeds were chosen: 1.11 m/s (9 s) and 0.55 m/s (18 s). A gait speed superior or equal to 1.11 m/s presents a positive predictive value of 86% to authorize to stop crutches. Below 0.55 m/s, the positive predictive value is 83% to keep crutches. Between these two speeds, the test of maximal gait speed does not help the clinician to decide to stop crutches. CONCLUSION: The test of maximal gait speed brings a help to decide to stop crutches only for speeds superior to 1.11 m/s.

Longitudinal changes in diffusion tensor-based quantitative MRI in multiple sclerosis.

OBJECTIVE: To estimate longitudinal changes in a quantitative whole-brain and tract-specific MRI study of multiple sclerosis (MS), with the intent of assessing the feasibility of this approach in clinical trials. METHODS: A total of 78 individuals with MS underwent a median of 3 scans over 2 years. Diffusion tensor imaging indices, magnetization transfer ratio, and T2 relaxation time were analyzed in supratentorial brain, corpus callosum, optic radiations, and corticospinal tracts by atlas-based tractography. Linear mixed-effect models estimated annualized rates of change for each index, and sample size estimates for potential clinical trials were determined. RESULTS: There were significant changes over time in fractional anisotropy and perpendicular diffusivity in the supratentorial brain and corpus callosum, mean diffusivity in the supratentorial brain, and magnetization transfer ratio in all areas studied. Changes were most rapid in the corpus callosum, where fractional anisotropy decreased 1.7% per year, perpendicular diffusivity increased 1.2% per year, and magnetization transfer ratio decreased 0.9% per year. The T2 relaxation time changed more rapidly than diffusion tensor imaging indices and magnetization transfer ratio but had higher within-participant variability. Magnetization transfer ratio in the corpus callosum and supratentorial brain declined at an accelerated rate in progressive MS relative to relapsing-remitting MS. Power analysis yielded reasonable sample sizes (on the order of 40 participants per arm or fewer) for 1- or 2-year trials. CONCLUSIONS: Longitudinal changes in whole-brain and tract-specific diffusion tensor imaging indices and magnetization transfer ratio can be reliably quantified, suggesting that small clinical trials using these outcome measures are feasible.

[Automated maintenance of a central file of blood donors]. / Gestion automatisée d'un fichier central de donneurs de sang.

Data processing of medical information gathered by the physician working in the mobile unit, has been optimized and automatized. Thanks to the simultaneous use of an optical mark reader and a lightpen it is possible to achieve a quick data entry without a manual keyboard as soon as the mobile blood units bring back the samples. The donnors' medical cards which accompany each blood sample are transmitted from the mobile unit to the laboratory for better test accuracy. This simple system, operating since October 1984, has proven its reliability and efficiency.

[Computerized management of a stock of blood products]. / Gestion automatisée d'un stock de produits sanguins.

We describe in this paper the management of the stock of perishable products in the Centre Departemental de Transfusion Sanguine des Hauts-de-Seine. The use of computer and Codabar labels enables a complete no-transcription system. The logical organisation of stock allows a better response to the specific needs of our customers. The progressive development of programmation enables a good adaptation of working methods and makes the setting of the system much easier in the blood bank.