Cerebral blood flow patterns in preterm and term neonates assessed with pseudo-continuous arterial spin labeling perfusion MRI.

In preterm (PT) infants, regional cerebral blood flow (CBF) disturbances may predispose to abnormal brain maturation even without overt brain injury. Therefore, it would be informative to determine the spatial distribution of grey matter (GM) CBF in PT and full-term (FT) newborns at term-equivalent age (TEA) and to assess the relationship between the features of the CBF pattern and both prematurity and prematurity-related brain lesions. In this prospective study, we obtained measures of CBF in 66 PT (51 without and 15 with prematurity-related brain lesions) and 38 FT newborns through pseudo-continuous arterial spin labeling (pCASL) MRI acquired at TEA.

Pathophysiology of multiple sclerosis damage and repair: Linking cerebral hypoperfusion to the development of irreversible tissue loss in multiple sclerosis using magnetic resonance imaging.

Background And Purpose: Reduced cerebral perfusion has been observed in multiple sclerosis (MS) and may contribute to tissue loss both acutely and chronically. Here, we test the hypothesis that hypoperfusion occurs in MS and relates to the presence of irreversible tissue damage.

Methods: In 91 patients with relapsing MS and 26 healthy controls (HC), gray matter (GM) cerebral blood flow (CBF) was assessed using pulsed arterial spin labeling.

Hemispheric functional segregation facilitates target detection during sustained visuospatial attention.

Visuospatial attention is strongly lateralized, with the right hemisphere commonly exhibiting stronger activation and connectivity patterns than the left hemisphere during attentive processes. However, whether such asymmetry influences inter-hemispheric information transfer and behavioral performance is not known. Here we used a region of interest (ROI) and network-based approach to determine steady-state fMRI functional connectivity (FC) in the whole cerebral cortex during a leftward/rightward covert visuospatial attention task.

Microwave techniques for electron cyclotron resonance plasma diagnostics.

This paper reviews the main microwave diagnostic techniques and tools adopted in electron cyclotron resonance (ECR) (and others) ion source laboratories, with a special focus on techniques and instruments developed at INFN-LNS. Along with the tools used for optimization of microwave launching (power monitors, spectral analysis, and network analyzers), this paper deals, in particular, with more recent devices on-purpose developed to perform in-plasma analysis, such as absolute density measurements and density profiles retrieval. Among these, the first example of microwave interferometry for ECR compact machines (the VESPRI interferometer at INFN-LNS) will be briefly discussed, in combination with microwave polarimetric techniques based on Faraday rotation detection.

Perception is associated with the brain's metabolic response to sensory stimulation.

Processing of incoming sensory stimulation triggers an increase of cerebral perfusion and blood oxygenation (neurovascular response) as well as an alteration of the metabolic neurochemical profile (neurometabolic response). Here, we show in human primary visual cortex (V1) that perceived and unperceived isoluminant chromatic flickering stimuli designed to have similar neurovascular responses as measured by blood oxygenation level-dependent functional magnetic resonance imaging (BOLD-fMRI) have markedly different neurometabolic responses as measured by proton functional magnetic resonance spectroscopy (1H-fMRS). In particular, a significant regional buildup of lactate, an index of aerobic glycolysis, and glutamate, an index of malate-aspartate shuttle, occurred in V1 only when the flickering was perceived, without any relation with other behavioral or physiological variables.

A flow-diffusion model of oxygen transport for quantitative mapping of cerebral metabolic rate of oxygen (CMRO) with single gas calibrated fMRI.

One promising approach for mapping CMRO is dual-calibrated functional MRI (dc-fMRI). This method exploits the Fick Principle to combine estimates of CBF from ASL, and OEF derived from BOLD-ASL measurements during arterial O and CO modulations. Multiple gas modulations are required to decouple OEF and deoxyhemoglobin-sensitive blood volume.

Evaluation of denoising strategies for task-based functional connectivity: Equalizing residual motion artifacts between rest and cognitively demanding tasks.

In-scanner head motion represents a major confounding factor in functional connectivity studies and it raises particular concerns when motion correlates with the effect of interest. One such instance regards research focused on functional connectivity modulations induced by sustained cognitively demanding tasks. Indeed, cognitive engagement is generally associated with substantially lower in-scanner movement compared with unconstrained, or minimally constrained, conditions.

Brain Network Modularity During a Sustained Working-Memory Task.

Spontaneous oscillations of the blood oxygenation level-dependent (BOLD) signal are spatially synchronized within specific brain networks and are thought to reflect synchronized brain activity. Networks are modulated by the performance of a task, even if the exact features and degree of such modulations are still elusive. The presence of networks showing anticorrelated fluctuations lend initially to suppose that a competitive relationship between the default mode network (DMN) and task positive networks (TPNs) supports the efficiency of brain processing.

Self-consistent electromagnetic analysis of the microwave-coupling of an electron cyclotron resonance-based charge breeder.

The Electron Cyclotron Resonance (ECR) Charge Breeding (CB) technique consists in transforming the charge state of an input beam from 1+ to n+ to allow post-acceleration. The optimization of an ECR-CB requires a deep investigation of ion dynamics and electron heating, the latter being influenced by the microwave-to-plasma coupling mechanism. In this paper, we report the electromagnetic analysis of the microwave-to-plasma coupling of the Selective Production of Exotic Species charge breeder (SPES-CB) plasma chamber, taking into account the presence of the plasma through its dielectric tensor, performed using a self-consistent approach.

Self-consistent modeling of beam-plasma interaction in the charge breeding optimization process.

The slowing down and capture by a plasma of externally injected 1+ ions, as a consequence of very frequent elastic Coulomb collisions, is the main mechanism involved in the charge breeding process based on electron cyclotron resonance ion sources. The Istituto Nazionale di Fisica Nucleare ion source group has been undertaking an intense activity on numerical simulations of the beam-plasma interaction, developing a code that has been proven to be very effective in reproducing several experimental results of charge breeding of light and heavy ions. This contribution will present the progress made in the development of the numerical code, focusing the attention on the latest simulations of charge breeding of Rb1+ ions employing a self-consistent plasma target model.

Influence of Repetitive Transcranial Magnetic Stimulation on Human Neurochemistry and Functional Connectivity: A Pilot MRI/MRS Study at 7 T.

Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive brain stimulation method commonly used in the disciplines of neuroscience, neurology, and neuropsychiatry to examine or modulate brain function. Low frequency rTMS (e.g.

Numerical simulation of the blood oxygenation level-dependent functional magnetic resonance signal using finite element method.

Since the introduction of functional magnetic resonance imaging (fMRI), several computational approaches have been developed to examine the effect of the morphology and arrangement of blood vessels on the blood oxygenation-level dependent (BOLD) signal in the brain. In the present work, we implemented the original Ogawa's model using a numerical simulation based on the finite element method (FEM) instead of the analytical models. In literature, there are different works using analytical methods to analyse the transverse relaxation rate ( ), which BOLD signal is related to, modelling the vascular system with simple and canonical geometries such as an infinite cylinder model (ICM) or a set of cylinders.

Experimental characterization of the AISHa ion source.

The Advanced Ion Source for Hadrontherapy (AISHa) has been designed to generate high brightness multiply charged ion beams for hadron therapy applications. AISHa is a compact electron cyclotron resonance ion source whose hybrid magnetic system consists of a permanent Halbach-type hexapole magnet and a set of independently energized superconducting coils. This has allowed us to achieve high performances in a cost effective way.

Brain Networks Underlying Eye's Pupil Dynamics.

Phasic changes in eye's pupil diameter have been repeatedly observed during cognitive, emotional and behavioral activity in mammals. Although pupil diameter is known to be associated with noradrenergic firing in the pontine Locus Coeruleus (LC), thus far the causal chain coupling spontaneous pupil dynamics to specific cortical brain networks remains unknown. In the present study, we acquired steady-state blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) data combined with eye-tracking pupillometry from fifteen healthy subjects that were trained to maintain a constant attentional load.

A Finite-Difference Approach for Plasma Microwave Imaging Profilometry.

Plasma diagnostics is a topic of great interest in the physics and engineering community because the monitoring of plasma parameters plays a fundamental role in the development and optimization of plasma reactors. Towards this aim, microwave diagnostics, such as reflectometric, interferometric, and polarimetric techniques, can represent effective means. Besides the above, microwave imaging profilometry (MIP) may allow the obtaining of tomographic, i.

Diffusion processes in microwave discharge ion source and consequences on the upgrade of existing ion sources.

Several experiments have shown that the insertion of insulator materials within the plasma chamber may lead to a general improvement of microwave discharge ion source performances. In particular, the insertion of alumina into the chamber walls and borum nitride into extraction and injection flanges permits to increase the extracted current and the proton fraction and leads to a general decrease in the beam ripple. These beneficial effects have been usually explained by considering the secondary electron emission of insulators hit by plasma electrons.

Corrigendum: Multi-modal Brain MRI in Subjects with PD and iRBD.

[This corrects the article on p. 709 in vol. 11, PMID: 29311789.

Scale-invariant rearrangement of resting state networks in the human brain under sustained stimulation.

Brain activity at rest is characterized by widely distributed and spatially specific patterns of synchronized low-frequency blood-oxygenation level-dependent (BOLD) fluctuations, which correspond to physiologically relevant brain networks. This network behaviour is known to persist also during task execution, yet the details underlying task-associated modulations of within- and between-network connectivity are largely unknown. In this study we exploited a multi-parametric and multi-scale approach to investigate how low-frequency fluctuations adapt to a sustained n-back working memory task.

Multi-modal Brain MRI in Subjects with PD and iRBD.

Idiopathic rapid eye movement sleep behavior disorder (iRBD) is a condition that often evolves into Parkinson's disease (PD). Therefore, by monitoring iRBD it is possible to track the neurodegeneration of individuals who may progress to PD. Here we aimed at piloting the characterization of brain tissue properties in mid-brain subcortical regions of 10 healthy subjects, 8 iRBD, and 9 early-diagnosed PD.

Disruption of Semantic Network in Mild Alzheimer's Disease Revealed by Resting-State fMRI.

Subtle semantic deficits can be observed in Alzheimer's disease (AD) patients even in the early stages of the illness. In this work, we tested the hypothesis that the semantic control network is deregulated in mild AD patients. We assessed the integrity of the semantic control system using resting-state functional magnetic resonance imaging in a cohort of patients with mild AD (n = 38; mean mini-mental state examination = 20.

Task-Related Modulations of BOLD Low-Frequency Fluctuations within the Default Mode Network.

Spontaneous low-frequency Blood-Oxygenation Level-Dependent (BOLD) signals acquired during resting state are characterized by spatial patterns of synchronous fluctuations, ultimately leading to the identification of robust brain networks. The resting-state brain networks, including the Default Mode Network (DMN), are demonstrated to persist during sustained task execution, but the exact features of task-related changes of network properties are still not well characterized. In this work we sought to examine in a group of 20 healthy volunteers (age 33 ± 6 years, 8 F/12 M) the relationship between changes of spectral and spatiotemporal features of one prominent resting-state network, namely the DMN, during the continuous execution of a working memory n-back task.

Temporal Information Entropy of the Blood-Oxygenation Level-Dependent Signals Increases in the Activated Human Primary Visual Cortex.

Time-domain analysis of blood-oxygenation level-dependent (BOLD) signals allows the identification of clusters of voxels responding to photic stimulation in primary visual cortex (V1). However, the characterization of information encoding into temporal properties of the BOLD signals of an activated cluster is poorly investigated. Here, we used Shannon entropy to determine spatial and temporal information encoding in the BOLD signal within the most strongly activated area of the human visual cortex during a hemifield photic stimulation.