Modelling the effects of propofol on neuronal synchronization in network of interneurons

International audiencePropofol is a chemical agent commonly used as an intravenous general anesthetic. At the cellular level, this short-acting ananesthetic positively modulates GABAergic inhibitory activity by targeting GABA-A receptors [1]. This type of receptors are widespread in the brain and can be present both within synaptic clefts, as well as on extrasynaptic locations along the dendrites and neuron membrane where they are responsible for tonic inhibition. At the macroscopic level of SEEG (deep Stereographic-Electro Encephalogram) or EEG (Electro Encephalogram) recordings, one observes, with certain doses of propofol, a paradoxical excitation phenomenon [2] the generation mechanisms of which are not clearly understood. In this study, we suggest a potential mechanism for the appearance of paradoxical excitation occurring under propofol-induced general anaesthesia. We show, with a model network of Hodgkin-Huxley neurons, that tonic inhibition – induced by the binding of propofol to extra-synaptic receptors – together with an increase of the synaptic time constant within an certain range [3] can account for the phenomenon of paradoxical excitation. However, changes in the gain (or conductance) of the synaptic inhibition do not correspond to a sudden increase in neuronal population firing rate nor synchrony as described in the experiments [3]. The action of propofol on extrasynaptic GABAergic receptors was modelled by varying the conductance g ton of a tonic current in the form $I ton = g ton (V − E ton)$ as described in [4]. Figure 1 shows the evolution of the neuronal population firing rate and the coherence (or synchrony) of the network activity as the tonic inhibition and the synaptic conductance vary. The plots are given for different values of the synaptic time constants. The increase of these three variables, synaptic time constant and conductance, and tonic conductance reflect an increase in propofol doses

Modelling human choices: MADeM and decision‑making

Research supported by FAPESP 2015/50122-0 and DFG-GRTK 1740/2. RP and AR are also part of the Research, Innovation and Dissemination Center for Neuromathematics FAPESP grant (2013/07699-0). RP is supported by a FAPESP scholarship (2013/25667-8). ACR is partially supported by a CNPq fellowship (grant 306251/2014-0)

Le présent et ses doubles

Le numéro 7 de la revue Res Futurae (printemps 2016) accueille un dossier issu de la journée d’études de la SELF XX-XXI (Société d’études de la littérature française des XXè et XXIè siècles ) : « Le présent et ses doubles » (30-31 janvier 2015), enrichi par de nouvelles contributions. Il s'agit d’explorer les modalités et les moyens par lesquels la littérature est à même de créer le paradoxe d’un « présentisme » inactuel, en établissant une tension entre deux temporalités, celle de l’éphémère et de l’immédiat, et celle de l’ailleurs et autre

Science-fiction et jeu vidéo

Lorsque Spacewar, considéré comme un des premiers jeux vidéo, voit le jour en 1962 dans les salles du Massachussets Institute of Technology, il marque le début d’une longue relation entre ce médium et la science-fiction. La thématique spatiale que ce précurseur exploite traverse encore une grande partie de la production vidéoludique. De l’émergence de cette culture hacker dans les années 1960 à la production actuelle, le jeu vidéo a constamment puisé dans les ressorts propres à la science-fiction. Ce numéro de Res Futurae entend interroger le lien intime qui unit le jeu vidéo à la science-fiction depuis des angles variés et selon une approche interdisciplinaire, en sollicitant des textes proposant une réflexion théorique ou analytique

Efficacy of Chest CT for COVID-19 Pneumonia Diagnosis in France

International audienceThe role and performance of chest CT in the diagnosis of the coronavirus disease 2019 (COVID-19) pandemic remains under active investigation. Purpose To evaluate the French national experience using chest CT for COVID-19, results of chest CT and reverse transcription polymerase chain reaction (RT-PCR) assays were compared together and with the final discharge diagnosis used as the reference standard. Materials and Methods A structured CT scan survey (NCT04339686) was sent to 26 hospital radiology departments in France between March 2, 2020, and April 24, 2020. These dates correspond to the peak of the national COVID-19 epidemic. Radiology departments were selected to reflect the estimated geographic prevalence heterogeneities of the epidemic. All symptomatic patients suspected of having COVID-19 pneumonia who underwent both initial chest CT and at least one RT-PCR test within 48 hours were included. The final discharge diagnosis, based on multiparametric items, was recorded. Data for each center were prospectively collected and gathered each week. Test efficacy was determined by using the Mann-Whitney test, Student t test, χ2 test, and Pearson correlation coefficient. P < .05 indicated a significant difference. Results Twenty-six of 26 hospital radiology departments responded to the survey, with 7500 patients entered; 2652 did not have RT-PCR test results or had unknown or excess delay between the RT-PCR test and CT. After exclusions, 4824 patients (mean age, 64 years ± 19 [standard deviation], 2669 male) were included. With final diagnosis as the reference, 2564 of the 4824 patients had COVID-19 (53%). Sensitivity, specificity, negative predictive value, and positive predictive value of chest CT in the diagnosis of COVID-19 were 2319 of 2564 (90%; 95% CI: 89, 91), 2056 of 2260 (91%; 95% CI: 91, 92), 2056 of 2300 (89%; 95% CI: 87, 90), and 2319 of 2524 (92%; 95% CI: 91, 93), respectively. There was no significant difference for chest CT efficacy among the 26 geographically separate sites, each with varying amounts of disease prevalence. Conclusion Use of chest CT for the initial diagnosis and triage of patients suspected of having coronavirus disease 2019 was successful