95 research outputs found
¿Se han modificado las preferencias de los ciudadanos sobre las políticas de bienestar en España (1985-2005)?
Este trabajo es uno de los frutos empíricos del proyecto de investigación Reformas en el Estado de Bienestar: Actores y Apoyos Ciudadanos (REBAAC), http://www.iesam.csic.es/proyecto/rebaac.htm, dirigido por Luis Moreno, que se completará en los próximos meses con otros escritos sobre el tema.[EN] In recent years pressures for the reform of the Welfare State have been voiced despite that public opinion has kept opposed to the retrenchment of social policies. Some studies have pointed out that governments have learned how to avoid popular resistance to the reforms due to a change in citizens’ attitudes. This Working Paper explores the attitudes of the Spaniards with respect to the process and outcomes of the welfare policies implemented in Spain in the last 20 years. Whenever possible this paper takes a comparative. Time series
have been worked out covering the period under analysis. Likewise, preferences towards the various welfare policies and these and other public policies are also compared. The two main conclusions are that the support for the welfare policies is solid (despite some qualifications) and that the public preference for the meso or intermediate level of government as provider of social policies has increased.[ES] En los últimos años parece que las presiones para la reforma del Estado de Bienestar están siendo más insistentes que una opinión pública hasta ahora opuesta a cualquier tipo de recorte de los programas sociales. Algunos estudios sugieren que los gobiernos parecen haber aprendido como esquivar la resistencia de los ciudadanos a las reformas aprovechando un supuesto cambio en sus actitudes durante los últimos años. Con esta hipótesis de cambio en las actitudes ciudadanas se exploran en este trabajo las preferencias de los españoles hacia el proceso y los resultados de las políticas del bienestar en los últimos veinte años. Siempre que es posible se sigue una estrategia comparativa. Por un lado, se han construido series temporales que cubren todo el periodo estudiado y, por otro, se comparan las preferencias entre las políticas de bienestar y entre éstas y el resto de las
políticas públicas. Las dos conclusiones más significativas son que, si bien con algunos matices, el apoyo a la provisión pública del bienestar continúa siendo muy sólido y crece también la preferencia por el nivel intermedio de gobierno como proveedor de tales programas de bienestar
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Quantitative investigation of the effect of the extra-cerebral vasculature in diffuse optical imaging: a simulation study
Diffuse optical imaging (DOI) is a non invasive technique allowing the recovery of hemodynamic changes in the brain. Due to the diffusive nature of photon propagation in turbid media and the fact that cerebral tissues are located around 1.5 cm under the adult human scalp, DOI measurements are subject to partial volume errors. DOI measurements are also sensitive to large pial vessels because oxygenated and deoxygenated hemoglobin are the dominant chromophores in the near infrared window. In this study, the effect of the extra-cerebral vasculature in proximity of the sagittal sinus was investigated for its impact on DOI measurements simulated over the human adult visual cortex. Numerical Monte Carlo simulations were performed on two specific models of the human head derived from magnetic resonance imaging (MRI) scans. The first model included the extra-cerebral vasculature in which constant hemoglobin concentrations were assumed while the second did not. The screening effect of the vasculature was quantified by comparing recovered hemoglobin changes from each model for different optical arrays and regions of activation. A correction factor accounting for the difference between the recovered and the simulated hemoglobin changes was computed in each case. The results show that changes in hemoglobin concentration are better estimated when the extra-cerebral vasculature is modeled and the correction factors obtained in this case were at least 1.4-fold lower. The effect of the vasculature was also examined in a high-density diffuse optical tomography configuration. In this case, the difference between changes in hemoglobin concentration recovered with each model was reduced down to 10%
CutFEM-based MEG forward modeling improves source separability and sensitivity to quasi-radial sources : A somatosensory group study
Source analysis of magnetoencephalography (MEG) data requires the computation of the magnetic fields induced by current sources in the brain. This so-called MEG forward problem includes an accurate estimation of the volume conduction effects in the human head. Here, we introduce the Cut finite element method (CutFEM) for the MEG forward problem. CutFEM's meshing process imposes fewer restrictions on tissue anatomy than tetrahedral meshes while being able to mesh curved geometries contrary to hexahedral meshing. To evaluate the new approach, we compare CutFEM with a boundary element method (BEM) that distinguishes three tissue compartments and a 6-compartment hexahedral FEM in an n = 19 group study of somatosensory evoked fields (SEF). The neural generators of the 20 ms post-stimulus SEF components (M20) are reconstructed using both an unregularized and a regularized inversion approach. Changing the forward model resulted in reconstruction differences of about 1 centimeter in location and considerable differences in orientation. The tested 6-compartment FEM approaches significantly increase the goodness of fit to the measured data compared with the 3-compartment BEM. They also demonstrate higher quasi-radial contributions for sources below the gyral crowns. Furthermore, CutFEM improves source separability compared with both other approaches. We conclude that head models with 6 compartments rather than 3 and the new CutFEM approach are valuable additions to MEG source reconstruction, in particular for sources that are predominantly radial.Peer reviewe
Neonatal brain resting-state functional connectivity imaging modalities
Infancy is the most critical period in human brain development. Studies demonstrate that subtle brain abnormalities during this state of life may greatly affect the developmental processes of the newborn infants. One of the rapidly developing methods for early characterization of abnormal brain development is functional connectivity of the brain at rest. While the majority of resting-state studies have been conducted using magnetic resonance imaging (MRI), there is clear evidence that resting-state functional connectivity (rs-FC) can also be evaluated using other imaging modalities. The aim of this review is to compare the advantages and limitations of different modalities used for the mapping of infants’ brain functional connectivity at rest. In addition, we introduce photoacoustic tomography, a novel functional neuroimaging modality, as a complementary modality for functional mapping of infants’ brain
CutFEM forward modeling for EEG source analysis
Introduction: Source analysis of Electroencephalography (EEG) data requires the computation of the scalp potential induced by current sources in the brain. This so-called EEG forward problem is based on an accurate estimation of the volume conduction effects in the human head, represented by a partial differential equation which can be solved using the finite element method (FEM). FEM offers flexibility when modeling anisotropic tissue conductivities but requires a volumetric discretization, a mesh, of the head domain. Structured hexahedral meshes are easy to create in an automatic fashion, while tetrahedral meshes are better suited to model curved geometries. Tetrahedral meshes, thus, offer better accuracy but are more difficult to create. Methods: We introduce CutFEM for EEG forward simulations to integrate the strengths of hexahedra and tetrahedra. It belongs to the family of unfitted finite element methods, decoupling mesh and geometry representation. Following a description of the method, we will employ CutFEM in both controlled spherical scenarios and the reconstruction of somatosensory-evoked potentials. Results: CutFEM outperforms competing FEM approaches with regard to numerical accuracy, memory consumption, and computational speed while being able to mesh arbitrarily touching compartments. Discussion: CutFEM balances numerical accuracy, computational efficiency, and a smooth approximation of complex geometries that has previously not been available in FEM-based EEG forward modeling.Peer reviewe
CutFEM forward modeling for EEG source analysis
IntroductionSource analysis of Electroencephalography (EEG) data requires the computation of the scalp potential induced by current sources in the brain. This so-called EEG forward problem is based on an accurate estimation of the volume conduction effects in the human head, represented by a partial differential equation which can be solved using the finite element method (FEM). FEM offers flexibility when modeling anisotropic tissue conductivities but requires a volumetric discretization, a mesh, of the head domain. Structured hexahedral meshes are easy to create in an automatic fashion, while tetrahedral meshes are better suited to model curved geometries. Tetrahedral meshes, thus, offer better accuracy but are more difficult to create.MethodsWe introduce CutFEM for EEG forward simulations to integrate the strengths of hexahedra and tetrahedra. It belongs to the family of unfitted finite element methods, decoupling mesh and geometry representation. Following a description of the method, we will employ CutFEM in both controlled spherical scenarios and the reconstruction of somatosensory-evoked potentials.ResultsCutFEM outperforms competing FEM approaches with regard to numerical accuracy, memory consumption, and computational speed while being able to mesh arbitrarily touching compartments.DiscussionCutFEM balances numerical accuracy, computational efficiency, and a smooth approximation of complex geometries that has previously not been available in FEM-based EEG forward modeling
Functional near-infrared spectroscopy in pediatric clinical research: Different pathophysiologies and promising clinical applications
International audienceOver its 30 years of existence, functional near-infrared spectroscopy (fNIRS) has matured into a highly versatile tool to study brain function in infants and young children. Its advantages, amongst others, include its ease of application and portability, the option to combine it with electrophysiology, and its relatively good tolerance to movement. As shown by the impressive body of fNIRS literature in the field of cognitive developmental neuroscience, the method's strengths become even more relevant for (very) young individuals who suffer from neurological, behavioral, and/or cognitive impairment. Although a number of studies have been conducted with a clinical perspective, fNIRS cannot yet be considered as a truly clinical tool. The first step has been taken in this direction by studies exploring options in populations with well-defined clinical profiles. To foster further progress, here, we review several of these clinical approaches to identify the challenges and perspectives of fNIRS in the field of developmental disorders. We first outline the contributions of fNIRS in selected areas of pediatric clinical research: epilepsy, communicative and language disorders, and attention-deficit/hyperactivity disorder. We provide a scoping review as a framework to allow the highlighting of specific and general challenges of using fNIRS in pediatric research. We also discuss potential solutions and perspectives on the broader use of fNIRS in the clinical setting. This may be of use to future research, targeting clinical applications of fNIRS in children and adolescents
Exploration de l'unité neurovasculaire dans l'épilepsie de l'enfant (approche multimodale haute densité couplant l'EEG à l'imagerie optique fonctionnelle)
L objectif de ce travail était d explorer l unité neurovasculaire épileptogène par une approche couplant l imagerie optique et EEG Haute Densité. Chez l animal, l imagerie optique mettait en évidence des modifications hémodynamiques débutant avant les pointes intercritiques. Chez l enfant, des modifications hémodynamiques complexes, associant variations du volume sanguin cérébral (qui pouvaient débuter avant les pointes épileptiques) à un couplage neurovasculaire, dont les caractéristiques différaient du modèle de Buxton, étaient observées, indifféremment, dans les épilepsies partielles, idiopathiques ou non. L analyse en temps-fréquence de l EEG retrouvait, des séquences hyper - désynchronisation, en miroir autour des pointes, dans les structures néocorticales et mésiales. Les modifications hémodynamiques et de synchronisation étaient spatialement concordantes avec le foyer épileptogène et apportaient des informations complémentaires sur la dynamique temporo-spatiale des réseaux intercritiques ainsi que sur les processus physiopathologiques liés aux pointes. Notre démarche, appliquée aux spasmes infantiles, retrouvait également des modifications hémodynamiques complexes (modifications du volume sanguin cérébral pouvant être suivies d un couplage neurovasculaire), qui suggéraient la mise en jeu d un réseau cortico-sous-corticale. Au total, l approche électro-hémodynamique développée apportait des éléments de compréhension sur les mécanismes physiopathologiques impliqués dans les pointes et des réseaux épileptiques, ouvrant de nouvelles perspectives sur des applications cliniques dans l identification du foyer épileptogène et du réseau intercritique des épilepsies partielles.We explored the epileptogenic neurovascular unit using a multimodal approach, coupling functional optical imaging and high density EEG. In an animal model, optical imaging highlighted hemodynamic changes which preceded interictal spikes. In children, complex hemodynamic changes, involving variations in cerebral blood volume (which could begin before epileptic spikes) and neurovascular coupling, which differed with the classical model described by Buxton, were observed, either in idiopathic or not idiopathic partial epilepsy. In time frequency domain, complex changes, consisted of alternating sequences of hyper-desynchronization, around epileptic spikes, in both mesial and neocortical structures were observed, regardless of the epileptic syndrome considered. Neuronal synchronization and hemodynamic changes were spatially concordant with the epileptogenic focus and provided additional information according to the temporo-spatial dynamic of interictal networks, like in pathophysiological processes associated with spikes. Our approach, applied to infantile spasms found initial changes in cerebral blood volume which could be followed by a neurovascular coupling suggesting the involvement of a complex cortico- subcortical network. In total, the multimodal approach developed about the epileptogenic neurovascular unit brought new understanding about the pathophysiological mechanisms involved in interictal spikes and in epileptic networks. In addition, the electro- hemodynamic approach opens new perspectives on clinical applications including the identification of epileptogenic focus and interictal network for pre-surgical assessment of partial refractory epilepsy.AMIENS-BU Santé (800212102) / SudocSudocFranceF
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