Multimodal functional neuroimaging: new insights from novel head modeling methodologies

2009/2010Neuroimaging plays a critically important role in neuroscience research and management of neurological and mental disorders. Modern neuroimaging techniques rely on various “source” signals that change across different spatial and temporal scales in accompany with neuronal activity. Nowadays, several types of noninvasive neuroimaging modalities are available based on biophysical signals related to either brain electrophysiology or hemodynamics/metabolism. In this dissertation, advanced model-based neuroimaging methods for the estimation of cortical brain activity from combined high-resolution electroencephalography (EEG), multimodal Magnetic Resonance Imaging (MRI) and functional Magnetic Resonance Imaging (fMRI) data are presented. The present dissertation begins with a review of the current state-of-the-art in the major neuroimaging techniques. Particular attention has been devoted to EEG modelling since such signals propagate (virtually) instantaneously from the activated neuronal tissues via volume conduction to the recording sites on/above the scalp surface. The instantaneous nature of EEG indicates an intrinsically high temporal resolution and precision, which make it well suited for studying brain functions on the neuronal time scale. The collective nature suggests low spatial resolution and specificity, which impede mapping brain functions in great regional details. However, this is regardless of recent advancements in electromagnetic source imaging, which has led to great strides in improving the EEG/MEG spatial resolution to a centimetre scale or even smaller. These methods entail: 1) modeling the brain electrical activity; 2) modeling the head volume conduction process so as to link the modeled electrical activity to EEG; and 3) reconstructing the brain electrical activity from recorded EEG data. For this aim, a subject's multicompartment head model (scalp, skull, CSF, brain cortex, white matter) is constructed from either individual magnetic resonance images or approximated geometry models. We compared different spherical and realistic head modelling techniques in estimating EEG forward solutions from current dipole sources distributed on a standard cortical space reconstructed from Montreal Neurological Institute (MNI) MRI data. Computer simulations are presented for three different four-shell head models, two with realistic geometry, either surface-based (BEM) or volume-based (FDM), and the corresponding sensor-fitted spherical-shaped model. Point Spread Function (PSF) and Lead Field (LF) cross-correlation analyses were performed for 26 symmetric dipole sources to quantitatively assess models’ accuracy in EEG source reconstruction. Both statistical and imaging analysis point to the realistic geometry as a relevant factor of improvement, particularly important when considering sources placed in the temporal or in the occipital cortex. In these situations, using a realistic head model will allow a better spatial discrimination of neural sources when compared to the spherical model. Moreover a brief overview of Diffusion Weighted Imaging and Diffusion Tensor Imaging is also given, as their application in modelling refinement is increasing the accuracy and the complexity of the brain models. Both fMRI and EEG represent brain activity in terms of a reliable anatomical localization and a detailed temporal evolution of neural signals. Simultaneous EEG-fMRI recordings offer the possibility to greatly enrich the significance and the interpretation of the single modality results because the same neural processes are observed from the same brain at the same time. Nonetheless, the different physical nature of the measured signals by the two techniques renders the coupling not always straightforward, especially in cognitive experiments where spatially localized and distributed effects coexist and evolve temporally at different temporal scales. The purpose of the last chapter is to illustrate the combination of simultaneously recorded EEG and fMRI signals exploiting the principles of EEG distributed source modelling. We define a common source space for fMRI and EEG signal projection and novel framework for the spatial and temporal comparative analysis. We use simultaneous EEG-fMRI in order to explore the relationship between the envelope of spontaneous neuronal oscillations in the alpha frequency band (8-13 Hz) recorded with EEG during eyes closed rest and spontaneous fluctuations of the fMRI BOLD signal. We showed on a single-subject analysis how the presented approach, when combined to an accurate realistic head modelling, is able to localize the alpha rhythmic modulation in the occipital visual area and the parieto-occipital sulcus. This finding is in line with recent studies, asserting that, within these regions, time-frequency analysis and phase-synchronization analysis indicated increased alpha power and alpha-band phase-synchronization in eyes-closed condition versus eyes-open condition. Given the lack in the scientific literature of group-analysis experimental studies performed with realistic modelling approach in this field, this topic will be further investigated in future work.XXII Ciclo198

ENSINO DE FILOSOFIA: DESAFIOS E POSSIBILIDADES DA DOCÊNCIA NO ENSINO MÉDIO NA CONTEMPORANEIDADE

Desde o retorno da obrigatoriedadeda disciplina de Filosofia ao Ensino Médio, a partirda homologação da Lei Nº 11.684, de 2 de Junho de 2008desafios são enfrentados na docência da disciplina,dentre estes estão a desvalorização da Filosofia, o preconceito e a discriminação da mesma enquanto disciplina do currículo.Um dado importante é que ao ingressar em um curso de licenciatura em Filosofia o estudante não tem presente a realidade escolar e curricular que muitas vezes desafia o docente quanto ao sentido do ensino de filosofia. O que regularmente acontece é que somente após o início do período de estágio obrigatório que há a possibilidade de experimentações práticas de organizar o planejamento para a atividade de ensino,também é nesse momento que nos deparamos com situações nada fáceis tanto para o docente quanto para o estagiário.Tais situações referem-se principalmente a recorrente necessidade de justificar a importância da filosofia perante as outras áreas do conhecimento. Pensamos que apartir desse contexto no qual a docência em filosofia está inserida é preciso problematizar e apontar de que modo é possível a filosofia na escola, considerando de que modo a multiplicidade existencial do jovem estudante do ensino médio interfere na docência da filosofia

Realistic and Spherical Head Modeling for EEG Forward Problem Solution: A Comparative Cortex-Based Analysis

The accuracy of forward models for electroencephalography (EEG) partly depends on head tissues geometry and strongly affects the reliability of the source reconstruction process, but it is not yet clear which brain regions are more sensitive to the choice of different model geometry. In this paper we compare different spherical and realistic head modeling techniques in estimating EEG forward solutions from current dipole sources distributed on a standard cortical space reconstructed from Montreal Neurological Institute (MNI) MRI data. Computer simulations are presented for three different four-shell head models, two with realistic geometry, either surface-based (BEM) or volume-based (FDM), and the corresponding sensor-fitted spherical-shaped model. Point Spread Function (PSF) and Lead Field (LF) cross-correlation analyses were performed for 26 symmetric dipole sources to quantitatively assess models' accuracy in EEG source reconstruction. Realistic geometry turns out to be a relevant factor of improvement, particularly important when considering sources placed in the temporal or in the occipital cortex

Cytomegalovirus infection in patients undergoing autologous peripheral blood stem cell transplantation

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Work engagement and psychological capital in the Italian public administration: A new resource-based intervention programme

Orientation: Organisations need energetic and dedicated employees to enhance the quality of their services and products continuously. According to the Conservation of Resources Theory, it is possible to increase work engagement of employees by improving their personal resources. Research purpose: The main aim of this study was to examine the extent to which an improvement in psychological capital, as a personal resource, might enhance work engagement of employees in the public sector. Motivation for the study: This study was developed to investigate how and to what extent interventions aiming at fostering higher work engagement through the enhancement of psychological capital were certainly effective. Research design, approach and method: To improve psychological capital, a new resource-based intervention programme (FAMILY intervention) was developed and applied, in which six dimensions \u2013 namely framing, attitudes, meaningfulness, identity, leading self and yoked together \u2013 were improved. A semi-experimental research design (pre-test and post-test) was used to conduct this study. Participants were 54 employees working in an Italian public health administration. In the pre-test and post-test stages, data were collected by using the psychological capital and work engagement scales. Main findings: Results showed that there is a positive relationship between psychological capital and work engagement in the pre-test and post-test stages, considered separately. In addition, comparing pre-test and post-test results revealed that the intervention programme significantly improved both psychological capital and work engagement. This shows that an improvement in psychological capital is consistent with an increase in work engagement. Conclusion: Together, these findings prove that psychological capital can be considered as a set of personal resources which lead to increased work engagement. Contribution/value-add: This study bridged the gap found in the literature between the role of psychological capital in fostering higher work engagement and the extent to which interventions are effective among employees working in public administration

Physical Origin of the Optical Degradation of InAs Quantum Dot Lasers

We present an extensive analysis of the physical mechanisms responsible for the degradation of 1.3-μm InAs quantum dot lasers epitaxially grown on Si, for application in silicon photonics. For the first time, we characterize the degradation of the devices by combined electro-optical measurements, electroluminescence spectra, and current-voltage analysis. We demonstrate the following original results: when submitted to a current step-stress experiment: 1) QD lasers show a measurable increase in threshold current, which is correlated to a decrease in slope efficiency; 2) the degradation process is stronger, when devices are stressed at current higher than 200 mA, i.e., in the stress regime, where both ground-state and excited-state emission are present; and 3) in the same range of stress currents, an increase in the defect-related current components is also detected, along with a slight decrease in the series resistance. Based on the experimental evidence collected within this paper, the degradation of QD lasers is ascribed to a recombination-enhanced defect reaction (REDR) process, activated by the escape of electrons out of the quantum dots

The Effect of Adjuvant Radiotherapy on One- and Two-Stage Prosthetic Breast Reconstruction and on Autologous Reconstruction: A Multicenter Italian Study among 18 Senonetwork Breast Centres

Purpose: In modern breast cancer treatment, a growing role has been observed for breast reconstruction together with an increase in clinical indications for postmastectomy radiotherapy (PMRT). Choosing the optimum type of reconstructive technique is a clinical challenge. We therefore conducted a national multicenter study to analyze the impact of PMRT on breast reconstruction. Methods: We conducted a retrospective case-control multicenter study on women undergoing breast reconstruction. Data were collected from 18 Italian Breast Centres and stored in a cumulative database which included the following: autologous reconstruction, direct-to-implant (DTI), and tissue expander/immediate (TE/I). For all patients, we described complications and surgical endpoints to complications such as reconstruction failure, explant, change in type of reconstruction, and reintervention. Results: From 2001 to April 2020, 3116 patients were evaluated. The risk for any complication was significantly increased in patients receiving PMRT (aOR, 1.73; 95% CI, 1.33-2.24; p < 0.001). PMRT was associated with a significant increase in the risk of capsular contracture in the DTI and TE/I groups (aOR, 2.24; 95% CI, 1.57-3.20; p < 0.001). Comparing type of procedures, the risk of failure (aOR, 1.82; 95% CI, 1.06-3.12, p=0.030), explant (aOR, 3.34; 95% CI, 3.85-7.83, p < 0.001), and severe complications (aOR, 2.54; 95% CI, 1.88-3.43, p < 0.001) were significantly higher in the group undergoing DTI reconstruction as compared to TE/I reconstruction. Conclusion: Our study confirms that autologous reconstruction is the procedure least impacted by PMRT, while DTI appears to be the most impacted by PMRT, when compared with TE/I which shows a lower rate of explant and reconstruction failure. The trial is registered with NCT04783818, and the date of registration is 1 March, 2021, retrospectively registered

Global disparities in surgeons’ workloads, academic engagement and rest periods: the on-calL shIft fOr geNEral SurgeonS (LIONESS) study

: The workload of general surgeons is multifaceted, encompassing not only surgical procedures but also a myriad of other responsibilities. From April to May 2023, we conducted a CHERRIES-compliant internet-based survey analyzing clinical practice, academic engagement, and post-on-call rest. The questionnaire featured six sections with 35 questions. Statistical analysis used Chi-square tests, ANOVA, and logistic regression (SPSS® v. 28). The survey received a total of 1.046 responses (65.4%). Over 78.0% of responders came from Europe, 65.1% came from a general surgery unit; 92.8% of European and 87.5% of North American respondents were involved in research, compared to 71.7% in Africa. Europe led in publishing research studies (6.6 ± 8.6 yearly). Teaching involvement was high in North America (100%) and Africa (91.7%). Surgeons reported an average of 6.7 ± 4.9 on-call shifts per month, with European and North American surgeons experiencing 6.5 ± 4.9 and 7.8 ± 4.1 on-calls monthly, respectively. African surgeons had the highest on-call frequency (8.7 ± 6.1). Post-on-call, only 35.1% of respondents received a day off. Europeans were most likely (40%) to have a day off, while African surgeons were least likely (6.7%). On the adjusted multivariable analysis HDI (Human Development Index) (aOR 1.993) hospital capacity &gt; 400 beds (aOR 2.423), working in a specialty surgery unit (aOR 2.087), and making the on-call in-house (aOR 5.446), significantly predicted the likelihood of having a day off after an on-call shift. Our study revealed critical insights into the disparities in workload, access to research, and professional opportunities for surgeons across different continents, underscored by the HDI