A stochastic model of the electrically stimulated auditory nerve: pulse-train response

Copyright © 1999 IEEE. Reprinted from IEEE Transactions on Biomedical Engineering, 46(6).This material is posted here with permission of the IEEE. Such permission of the IEEE does not in any way imply IEEE endorsement of any of The University of Melbourne's products or services. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to [email protected] choosing to view this document, you agree to all provisions of the copyright laws protecting it.The single-pulse model of the companion paper [1] is extended to describe responses to pulse trains by introducing a phenomenological refractory mechanism. Comparisons with physiological data from cat auditory nerve fibers are made for pulse rates between 100 and 800 pulses/s. First, it is shown that both the shape and slope of mean discharge rate curves are better predicted by the stochastic model than by the deterministic model. Second, while interpulse effects such as refractory effects do indeed increase the dynamic range at higher pulse rates, both the physiological data and the model indicate that much of the dynamic range for pulse-train stimuli is due to stochastic activity. Third, it is shown that the stochastic model is able to predict the general magnitude and behavior of variance in discharge rate as a function of pulse rate, while the deterministic model predicts no variance at all

A stochastic model of the electrically stimulated auditory nerve: single-pulse response

Copyright © 1999 IEEE. Reprinted from IEEE Transactions on Biomedical Engineering, 46(6).This material is posted here with permission of the IEEE. Such permission of the IEEE does not in any way imply IEEE endorsement of any of The University of Melbourne's products or services. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to [email protected] choosing to view this document, you agree to all provisions of the copyright laws protecting it.Most models of neural response to electrical stimulation, such as the Hodgkin-Huxley equations, are deterministic, despite significant physiological evidence for the existence of stochastic activity. For instance, the range of discharge probabilities measured in response to single electrical pulses cannot be explained at all by deterministic models. Furthermore, there is growing evidence that the stochastic component of auditory nerve response to electrical stimulation may be fundamental to functionally significant physiological and psychophysical phenomena. In this paper we present a simple and computationally efficient stochastic model of single-fiber response to single biphasic electrical pulses, based on a deterministic threshold model of action potential generation. Comparisons with physiological data from cat auditory nerve fibers are made, and it is shown that the stochastic model predicts discharge probabilities measured in response to single biphasic pulses more accurately than does the equivalent deterministic model. In addition, physiological data show an increase in stochastic activity with increasing pulse width of anodic/cathodic biphasic pulses, a phenomenon not present for monophasic stimuli. These and other data from the auditory nerve are then used to develop a population model of the total auditory nerve, where each fiber is described by the single-fiber model

150 ans d’évolution contextualisée des pressions et de l’état du milieu marin sur le littoral Marseillais : méthode BEEST

International audienceLe projet BEEST est un projet de Recherche et Développement reposant sur une démarche exploratoire. Celle-ci a pour ambition le développement d’une méthode de mise en contexte (spatiale et historique) des évolutions de la qualité des eaux et de la biodiversité côtières, en rapport avec les aménagements relatifs à l’assainissement et aux traitements des eaux urbaines, mais également en considérant l’évolution socio-économique du territoire. Le projet repose sur une base bibliographique : mesures existantes issues de l'autosurveillance, connaissances du gestionnaire assainissement, travaux universitaires des partenaires biologistes ou géographes, mais également sur des résultats des études disponibles et d‘approches historiques. Ces données consolidées, sont mises en perspective historique à l’échelle de la baie maritime et terrestre de Marseille. La méthode a pour but d'organiser les données afin de les exploiter sous un nouvel angle, notamment en mettant en perspective l'anthropoécosystème de Marseille et son histoire environnementale. En mettant en scène les évolutions du couple pressions-états, l’objectif est de mieux comprendre les co-évolutions homme-nature et d’apporter des éléments complémentaires à ceux existant déjà pour orienter les politiques publiques de gestion du milieu et du territoire

Geospatial analysis of Plasmodium falciparum serological indicators: school versus community sampling in a low-transmission malaria setting

Abstract Background Due to low numbers of active infections and persons presenting to health facilities for malaria treatment, case-based surveillance is inefficient for understanding the remaining disease burden in low malaria transmission settings. Serological data through the detection of IgG antibodies from previous malaria parasite exposure can fill this gap by providing a nuanced picture of where sustained transmission remains. Study enrollment at sites of gathering provides a potential approach to spatially estimate malaria exposure and could preclude the need for more intensive community-based sampling. Methods This study compared spatial estimates of malaria exposure from cross-sectional school- and community-based sampling in Haiti. A total of 52,405 blood samples were collected from 2012 to 2017. Multiplex bead assays (MBAs) tested IgG against P. falciparum liver stage antigen-1 (LSA-1), apical membrane antigen 1 (AMA1), and merozoite surface protein 1 (MSP1). Predictive geospatial models of seropositivity adjusted for environmental covariates, and results were compared using correlations by coordinate points and communes across Haiti. Results Consistent directional associations were observed between seroprevalence and environmental covariates for elevation (negative), air temperature (negative), and travel time to urban centers (positive). Spearman’s rank correlation for predicted seroprevalence at coordinate points was lowest for LSA-1 (ρ = 0.10, 95% CI: 0.09–0.11), but improved for AMA1 (ρ = 0.36, 95% CI: 0.35–0.37) and MSP1 (ρ = 0.48, 95% CI: 0.47–0.49). Conclusions In settings approaching P. falciparum elimination, case-based prevalence data does not provide a resolution of ongoing malaria transmission in the population. Immunogenic antigen targets (e.g., AMA1, MSP1) that give higher population rates of seropositivity provide moderate correlation to gold standard community sampling designs and are a feasible approach to discern foci of residual P. falciparum transmission in an area

DataSheet_1_Spatial, environmental, and individual associations with Anopheles albimanus salivary antigen IgG in Haitian children.docx

IgG serology can be utilized to estimate exposure to Anopheline malaria vectors and the Plasmodium species they transmit. A multiplex bead-based assay simultaneously detected IgG to Anopheles albimanus salivary gland extract (SGE) and four Plasmodium falciparum antigens (CSP, LSA-1, PfAMA1, and PfMSP1) in 11,541 children enrolled at 350 schools across Haiti in 2016. Logistic regression estimated odds of an above-median anti-SGE IgG response adjusting for individual- and environmental-level covariates. Spatial analysis detected statistically significant clusters of schools with students having high anti-SGE IgG levels, and spatial interpolation estimated anti-SGE IgG levels in unsampled locations. Boys had 11% (95% CI: 0.81, 0.98) lower odds of high anti-SGE IgG compared to girls, and children seropositive for PfMSP1 had 53% (95% CI: 1.17, 2.00) higher odds compared to PfMSP1 seronegatives. Compared to the lowest elevation, quartiles 2-4 of higher elevation were associated with successively lower odds (0.81, 0.43, and 0.34, respectively) of high anti-SGE IgG. Seven significant clusters of schools were detected in Haiti, while spatially interpolated results provided a comprehensive picture of anti-SGE IgG levels in the study area. Exposure to malaria vectors by IgG serology with SGE is a proxy to approximate vector biting in children and identify risk factors for vector exposure.</p

Additional file 1 of Geospatial analysis of Plasmodium falciparum serological indicators: school versus community sampling in a low-transmission malaria setting

Additional file 1: Table S1. Remote sensing data: resolutions, units, and sources. Table S2. Prevalence of positive rapid diagnostic test results with 95% confidence intervals by survey year for Tracking Results Continuously versus Transmission Assessment Surveys. Table S3. Observed seropositivity to P. falciparum antigens by survey year with 95% confidence intervals for community members surveyed for Tracking Results Continuously, 2012-2017. Table S4. Descriptive statistics of survey-site temporal covariates. Table S5. Descriptive statistics of survey-site static covariates. Table S6. Mean estimated coefficients of covariates with 95% credible intervals