DEFAULT MODE NETWORK AND WORKING MEMORY NETWORK DURING AN FMRI WORKING MEMORY TASK: DIFFERENCES AND CORRELATIONS WITH BEHAVIORAL PERFORMANCE

INTRODUCTION Previous neuroimaging studies have shown that working memory load has marked effects on regional neural activation[1-5]. However, the mechanism through which working memory load modulates brain connectivity is still unclear. During a working memory task, two of the most involved networks are the default mode network (DMN) and the working memory network (WMN)[6-7]: the selective focus on these networks can be useful in better understanding the load effects. Spatial independent component analysis (ICA)[8] has becomes a reliable technique to investigate the networks involved during an fMRI task, as it extracts spatiotemporal patterns of neural activity maximizing spatial independence. A specific study, conducted with ICA, investigating on how the load and phase of a working memory task are related with the activation and response time, is nowadays lacking. The aim of this work is to use the time course of DMN and WMN, selected by means of ICA, for studying: a) how these networks are involved with the complexity of the task and the phase; b) how, in these networks, complexity and phase are correlated with reaction times. METHODS MR Data Acquisition and preprocessing Fifteen young adult healthy and right-handed were involved. The MR protocol consisted of one anatomical sequence 3D T1-weighted MP-RAGE (Voxel size: 1 x 1 x 1 mm) and three functional acquisitions of 15 minutes each performed with a T2*-weighted EPI sequence (TR/TE: 1500/30, In- plane resolution: 3.5x3.5 mm, Thickness: 3.5 mm, Nr of slices: 24, Field of view: 64 x 64 mm). All the images were collected with a Siemens Allegra 3T MR scanner (Siemens, Erlangen, Germany) and a standard head coil. During the fMRI acquisition the subjects performed a delayed spatial working memory paradigm presented with three levels of difficulty. The memory set consisted of one, three or five circles presented randomly in different locations and to the subjects were asked to judge whether or not a given target stimulus had been part of a previous memory stimulus set. Every experiment consisted of 90 working memory trials, 30 per load, divided in three runs. Data were analyzed with Brain Voyager QX. 2.4 (Brain Innovation, Maastricht, The Netherlands). FMRI preprocessing included: 3D head-motion correction, slice-scan time correction, spatial smoothing, temporal high pass filter and linear trend removal. Anatomic 3D data set was inhomogeneities corrected, filtered and transformed into Talairach coordinates and coregistered with the functional information. Independent Component Analysis This analysis was conducted using Brainvoyager QX 2.4. ICA analysis was performed on each subject\u2019s three functional acquisitions. A subsequent total ICA group analysis[9-10] was achieved by an inter- subject ICA group analysis of all the intra-subject ICA group analysis. From the obtained maps were selected two Independent Components (ICs) containing the WMN[1,2]: WMN1 defined by SPL and Precuneus, and WMN2 with DLPFC and IPS (Fig. 1b-c). Also one IC describing the DMN was considered, with PCC, IPL and MPFC (Fig. 1a)[11]. For each run of all the subjects the ICs time course was considered: three time windows of 3TR (4.5s) for each working memory task phase (encode, maintenance and retrieval) were selected taking into account the haemodynamic response by delaying the window of 5 volumes events from the start of every trial. The window time course was corrected for a baseline value. Mean values of the ICs where examined and a subsequent correlation between the mean values and the response time in every trial was estimated. A 3x3 two-way ANOVA on Fisher transformed correlation was conducted to test the variation of loads (load1=less complex, load3=more complex), phases and runs. Figure 1: Networks selected from ICA analysis (transversal view): (a) DMN, (b) WMN1 (c) WMN2. RESULTS Figure 2 exhibits window mean activities and correlations divided for phase and load. DMN mean activity is negative while WMN1-2 mean activities have opposite behaviors regarding the phase, but similar concerning with the complexity (Fig. 2a-c). DMN shows a reduction of the correlation from encode to retrieval, instead of WM1-2 where it grows (Fig. 2d-f). The ANOVA showed significant variation for the phases over all the subjects in WMN1-2, an interaction of the variation of phases and runs in WMN2 and a interaction of phases, runs and loads in DMN. DISCUSSION These findings suggest that working memory networks (WMNs), as isolated by means of IC A, display substantially opposed mean values related to a different areas specialization. WMN1 seems to be more involved in the first part of the mnemonic phase and the amount of this involvement is associated to the trial: the more complicated the task, the higher the activation with respect to baseline. On the other hand, WMN2 increases from the first to the last part of the trial and is probably more involved in the operation of retrieval. In Figure 2e-f it is also shown that in the retrieval there is a stronger correlation between WMN1-2 mean values and the response time probably because this phase is the more complex. DMN exhibits, over all the phases, smaller than zero mean values (due to the task inducted deactivation). In contrast, its correlation has a different trend and increases above zero during the maintenance, probably due to the free thought of this phase. The different behavior of load 3 is probably due to the fact that this type of complexity is totally different from the other two. In conclusion, this study shows that, by means of ICA, it is possible to isolate networks of connected regions and relate their time courses to task phases and behavioral performance. This is a promising approach to advance the understanding of connectivity modulations in several brain networks, including WMNs and DMN

Hardware prototyping and validation of a W-ΔDOR digital signal processor

Microwave tracking, usually performed by on ground processing of the signals coming from a spacecraft, represents a crucial aspect in every deep-space mission. Various noise sources, including receiver noise, affect these signals, limiting the accuracy of the radiometric measurements obtained from the radio link. There are several methods used for spacecraft tracking, including the Delta-Differential One-Way Ranging (ΔDOR) technique. In the past years, European Space Agency (ESA) missions relied on a narrowband ΔDOR system for navigation in the cruise phase. To limit the adverse effect of nonlinearities in the receiving chain, an innovative wideband approach to ΔDOR measurements has recently been proposed. This work presents the hardware implementation of a new version of the ESA X/Ka Deep Space Transponder based on the new tracking technique named Wideband ΔDOR (W-ΔDOR). The architecture of the new transponder guarantees backward compatibility with narrowband ΔDOR

Super-crystals in composite ferroelectrics

As atoms and molecules condense to form solids, a crystalline state can emerge with its highly ordered geometry and subnanometric lattice constant. In some physical systems, such as ferroelectric perovskites, a perfect crystalline structure forms even when the condensing substances are non-stoichiometric. The resulting solids have compositional disorder and complex macroscopic properties, such as giant susceptibilities and non-ergodicity. Here, we observe the spontaneous formation of a cubic structure in composite ferroelectric potassium– lithium–tantalate–niobate with micrometric lattice constant, 104 times larger than that of the underlying perovskite lattice. The 3D effect is observed in specifically designed samples in which the substitutional mixture varies periodically along one specific crystal axis. Laser propagation indicates a coherent polarization super-crystal that produces an optical X-ray diffractometry, an ordered mesoscopic state of matter with important implications for critical phenomena and applications in miniaturized 3D optical technologies

Swallowing evaluation with videofluoroscopy in the paediatric population

Paediatric swallowing disorders can have several causes, from prematurity and congenital anomalies to gastro-oesophageal reflux and infective or inflammatory pathologies of the upper digestive tract. In neonates, the swallowing process is reflexive and involuntary. Later in infancy, the oral phase comes under voluntary control, while the pharyngeal phase and oesophageal phases remain involuntary. Swallowing difficulties can severely compromise pulmonary health and nutritional intake of paediatric patients. Videofluoroscopic Swallow Study (VFSS) is a radiographic procedure that provides a dynamic view of the swallowing process and is frequently considered to be definitive evaluation for objective assessment of dysphagia in paediatric patients. This review focuses on the different possible aetiologies of paediatric swallowing disorders and related videofluoroscopic swallowing study procedures and appearances

Participatory analysis of sustainable land and water management practices for integrated rural development in Myanmar

Besides providing reliable water resources for agricultural production, rural development efforts in Myanmar should target rural water security in terms of safe water supply and sanitation, and by mitigating water-related hazards. However, very few studies are available over the status of water-related development in rural areas of the country, and consequently on suitable practical solutions. The present paper describes a participatory workshop undertaken involving 45 rural development officers of the Department of Rural Development (DRD) of the Ministry of Agriculture, Livestock and Irrigation (MOALI), aimed at identifying suitable sustainable land and water management (SLWM) practices to be developed in rural areas of the country. Adoption of water safety plans (WSP), water harvesting, and soil and water bioengineering were strongly supported, while the need for improving water sanitation, especially in the poorest areas, was made evident. Insights of the participatory process confirmed that the poorest regions of Myanmar have also the worst water management structures. The results of the present work can represent baseline information and a needs assessment for future development projects in the country. However, there is a strong need for more studies and reports targeting marginalized rural contexts of Myanmar, to support equitable development

OpenSeesPy-based web application for pushover curve computation of RC bridge piers subject to arbitrarily non-uniform corrosion patterns

Existing reinforced concrete (RC) bridge piers are often subject to complex spatially non-uniform steel corrosion patterns typically due to water percolation and exposition to environmental agents. This produces degradation of strength and ductility of the pier, which may significantly influence the seismic performances of bridges. The computation of pushover curves of corroded RC piers can be carried out by fiber-beam-column elements combined with suitable degradation laws for the uniaxial materials. For this purpose, a multi-level fiber-based modeling procedure is proposed based on a partition of the pier into zones characterized by different cross-sections with fiber discretizations reproducing the sectional deterioration pattern. A web application based on OpenSeesPy is defined to implement this procedure. This includes an interface developed by React JS and Boostrap V5 and an APIs layer based on the Flask framework. Through the interface, users can insert the parameters needed for the structural response simulation, which is, then, performed by employing the numerical procedure developed in Python. At the end of the computation, users can visualize and download the results or vary the input parameters to perform new simulations. The web application runs in a Docker container, making it easy to deploy on cloud platforms or on-premises solutions. Numerical simulations of real specimens affected by material deterioration are performed

Simultaneous Extraction of the Fermi constant and PMNS matrix elements in the presence of a fourth generation

Several recent studies performed on constraints of a fourth generation of quarks and leptons suffer from the ad-hoc assumption that 3 x 3 unitarity holds for the first three generations in the neutrino sector. Only under this assumption one is able to determine the Fermi constant G_F from the muon lifetime measurement with the claimed precision of G_F = 1.16637 (1) x 10^-5 GeV^-2. We study how well G_F can be extracted within the framework of four generations from leptonic and radiative mu and tau decays, as well as from K_l3 decays and leptonic decays of charged pions, and we discuss the role of lepton universality tests in this context. We emphasize that constraints on a fourth generation from quark and lepton flavour observables and from electroweak precision observables can only be obtained in a consistent way if these three sectors are considered simultaneously. In the combined fit to leptonic and radiative mu and tau decays, K_l3 decays and leptonic decays of charged pions we find a p-value of 2.6% for the fourth generation matrix element |U_{e 4}|=0 of the neutrino mixing matrix.Comment: 19 pages, 3 figures with 16 subfigures, references and text added refering to earlier related work, figures and text in discussion section added, results and conclusions unchange