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Search Results: 1 - 10 of 193339 matches for " Frédéric D Broccard "
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Characterization of the time course of changes of the evoked electrical activity in a model of a chemically-induced neuronal plasticity
Frédéric D Broccard, Silvia Pegoraro, Maria Ruaro, Claudio Altafini, Vincent Torre
BMC Research Notes , 2009, DOI: 10.1186/1756-0500-2-13
Abstract: In the present manuscript we analysed the time course of changes of the evoked electrical activity during neuronal plasticity and we correlated it with a transcriptional analysis of the underlying changes of gene expression. Our investigation shows that treatment for 30 min. with the GABAA receptor antagonist gabazine (GabT) causes a potentiation of the evoked electrical activity occurring 2–4 hours after GabT and the concomitant up-regulation of 342 genes. Inhibition of the ERK1/2 pathway reduced but did not abolish the potentiation of the evoked response caused by GabT. In fact not all the genes analysed were blocked by ERK1/2 inhibitors.These results are in agreement with the notion that neuronal plasticity is mediated by several distinct pathways working in unison.We have used dissociated neuronal cultures grown over MEA for 2–6 weeks to monitor the electrical activity from a population of neurons [9]. MEAs allow stable and long lasting recordings (hours to days) of extracellular signals from the entire population and permit to characterize and follow the properties of single spikes from identified neurons. In this way, it was possible to describe the global properties of the network, such as its overall electrical activity and to obtain a characterization of changes during neuronal plasticity of single identified spikes. This analysis could not be performed with hippocampal slices or organotypic cultures grown on MEAs or in vivo, because in these cases local field potentials (LFPs) are observed and a detailed investigation of neuronal plasticity at a single spike level is almost impossible. We increased synaptic efficacy and the overall electrical activity by treating hippocampal cultures for 30 min. with the GABAA receptor antagonist gabazine (GabT). After GabT, gabazine was washed out and the time course of evoked electrical activity was followed/studied. MEA's extracellular electrodes were used for recording and stimulation so to quantify changes of the evok
On the Dynamics of the Spontaneous Activity in Neuronal Networks
Alberto Mazzoni, Frédéric D. Broccard, Elizabeth Garcia-Perez, Paolo Bonifazi, Maria Elisabetta Ruaro, Vincent Torre
PLOS ONE , 2007, DOI: 10.1371/journal.pone.0000439
Abstract: Most neuronal networks, even in the absence of external stimuli, produce spontaneous bursts of spikes separated by periods of reduced activity. The origin and functional role of these neuronal events are still unclear. The present work shows that the spontaneous activity of two very different networks, intact leech ganglia and dissociated cultures of rat hippocampal neurons, share several features. Indeed, in both networks: i) the inter-spike intervals distribution of the spontaneous firing of single neurons is either regular or periodic or bursting, with the fraction of bursting neurons depending on the network activity; ii) bursts of spontaneous spikes have the same broad distributions of size and duration; iii) the degree of correlated activity increases with the bin width, and the power spectrum of the network firing rate has a 1/f behavior at low frequencies, indicating the existence of long-range temporal correlations; iv) the activity of excitatory synaptic pathways mediated by NMDA receptors is necessary for the onset of the long-range correlations and for the presence of large bursts; v) blockage of inhibitory synaptic pathways mediated by GABAA receptors causes instead an increase in the correlation among neurons and leads to a burst distribution composed only of very small and very large bursts. These results suggest that the spontaneous electrical activity in neuronal networks with different architectures and functions can have very similar properties and common dynamics.
What Are the Ethical Problems Raised by the Increase of Cognitive Capabilities in the Defence Structure: The French Legal Structure, the Ethical Position of the French Military Health Service  [PDF]
Marion Trousselard, Frédéric Canini
Psychology (PSYCH) , 2015, DOI: 10.4236/psych.2015.64047
Abstract: All contemporary discussions concerning the ethics of human experimentation are grounded in the Nuremberg Code (Macklin, 1992) which listed what for many are the basic principles underlying the ethical conduct of human research. By law all scientific researches that use human research volunteers are governed by regulations prescribing the ethical treatment of these volunteers (Jones, 1993). The present purpose concerns what Ethics is in order to discuss about how military researches are directly affected by these regulations. They particularly concern neurosciences and precisely how to improve cognition for military individuals. Main arsenal was discussed according the risk-benefit balance. Furthermore, implications for medical reflexion were proposed. The French law prescribing the ethical principles for conducting research on humans as animals have been successively defined in accordance with European texts (French Public Health Code, 1994, 2004; Favre, Vallet, Renaudeau et al., 2004). All of these have consequences for conducting the French biomedical research for the defence.
Combining Internal Data with Scenario Analysis  [PDF]
Elias Karam, Frédéric Planchet
Modern Economy (ME) , 2015, DOI: 10.4236/me.2015.65055
Abstract: A Bayesian inference approach offers a methodical concept that combines internal data with experts’ opinions. Joining these two elements with precision is certainly one of the challenges in operational risk. In this paper, we are interested in applying a Bayesian inference technique in a robust manner to be able to estimate a capital requirement that best approaches the reality. In addition, we illustrate the importance of a consistent scenario analysis in showing that the expert opinion coherence leads to a robust estimation of risk.
Improvement of Bare Soil Semi-Empirical Radar Backscattering Models (Oh and Dubois) with SAR Multi-Spectral Satellite Data (X-, C- and L-Bands)  [PDF]
Rémy Fieuzal, Frédéric Baup
Advances in Remote Sensing (ARS) , 2016, DOI: 10.4236/ars.2016.54023
Abstract: The objective of this study is to improve the performance of semi-empirical radar backscatter models, which are mainly used in microwave remote sensing (Oh 1992, Oh 2004 and Dubois). The study is based on satellite and ground data collected on bare soil surfaces during the Multispectral Crop Monitoring experimental campaign of the CESBIO laboratory in 2010 over an agricultural region in southwestern France. The dataset covers a wide range of soil (viewing top soil moisture, surface roughness and texture) and satellite (at different frequencies: X-, C- and L-bands, and different incidence angles: 24.3° to 53.3°) configurations. The proposed methodology consists in identifying and correcting the residues of the models, depending on the surface properties (roughness, moisture, texture) and/or sensor characteristics (frequency, incidence angle). Finally, one model has been retained for each frequency domain. Results show that the enhancements of the models significantly increase the simulation performances. The coefficient of correlation increases of 23% in mean and the simulation errors (RMSE) are reduced to below 2 dB (at the X and C-bands) and to 1 dB at the L-band, compared to the initial models. At the X- and C-bands, the best performances of the modified models are provided by Dubois, whereas Oh 2004 is more suitable for the L-band (r is equal to 0.69, 0.65 and 0.85). Moreover, the modified models of Oh 1992 and 2004 and Dubois, developed in this study, offer a wider domain of validity than the initial formalism and increase the capabilities of retrieving the backscattering signal in view of applications of such approaches to stronglycontrasted agricultural surface states.
Quantitative Evaluation of the Lifshitz-Type Temperature Effect on the Casimir Force  [PDF]
Frédéric Schuller, Renaud Savalle
Journal of Modern Physics (JMP) , 2017, DOI: 10.4236/jmp.2017.811105
Abstract: We consider the extension of the Casimir effect to finite temperatures in the ideal case of perfectly reflecting plates. We apply Lifshitz’s theory in its Dzyaloshinskii version, and calculate the resulting force numerically for various plate distances. We show that the limiting expression found in the literature corresponds to unrealistic values of the parameters for which the force is too small to be measurable. Preliminary remark: There exists a huge literature on the Casimir effect both theoretical and experimental. In this note we concentrate on a particular point of the subject, quoting only references directly related to this point.
The Geomagnetic Effects of Solar Activity as Measured at Ouagadougou Station  [PDF]
Aristide Marie Frédéric Gyébré, Doua Allain Gnabahou, Frédéric Ouattara
International Journal of Astronomy and Astrophysics (IJAA) , 2018, DOI: 10.4236/ijaa.2018.82013
Abstract: The coronal mass ejections (CMEs) produce by Sun poloidal magnetic fields contribute to geomagnetic storms. The geomagnetic storm effects produced by one-day-shock, two-days-shock and three-days-shock activities on Ouagadougou station F2 layer critical frequency time variation are analyzed. It is found that during the solar minimum and the increasing phases, the shock activity produces both positive and negative storms. The positive storm is observed during daytime. At the solar maximum and the decreasing phases only the positive storm is produced. At the solar minimum there is no three-days-shock activity. During the solar increasing phase the highest amplitude of the storm effect is due to the one-day-shock activity and the lowest is produced by the two-days-shock activity. At the solar maximum phase the ionosphere electric current system is not affected by the shock activity. Nevertheless, the highest amplitude of the storm effect is caused by the two-days-shock activity and the lowest by the one-day-shock activity. During the solar decreasing phase, the highest amplitude provoked by the storm is due to the three-days-shock activity and the lowest by the one-day-shock activity.
The Alarming Proximity of Parasites
Frédéric Thomas
PLOS Biology , 2012, DOI: 10.1371/journal.pbio.1000526
Army Ants Trapped by Their Evolutionary History
Frédéric Delsuc
PLOS Biology , 2012, DOI: 10.1371/journal.pbio.0000037
A New Calibrated Bayesian Internal Goodness-of-Fit Method: Sampled Posterior p-Values as Simple and General p-Values That Allow Double Use of the Data
Frédéric Gosselin
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0014770
Abstract: Recent approaches mixing frequentist principles with Bayesian inference propose internal goodness-of-fit (GOF) p-values that might be valuable for critical analysis of Bayesian statistical models. However, GOF p-values developed to date only have known probability distributions under restrictive conditions. As a result, no known GOF p-value has a known probability distribution for any discrepancy function.
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