Spike Onset Dynamics and Response Speed in Neuronal Populations

Recent studies of cortical neurons driven by fluctuating currents revealed cutoff frequencies for action potential encoding of several hundred Hz. Theoretical studies of biophysical neuron models have predicted a much lower cutoff frequency of the order of average firing rate or the inverse membrane time constant. The biophysical origin of the observed high cutoff frequencies is thus not well understood. Here we introduce a neuron model with dynamical action potential generation, in which the linear response can be analytically calculated for uncorrelated synaptic noise. We find that the cutoff frequencies increase to very large values when the time scale of action potential initiation becomes short

The Atlas Liquid Argon Calorimeter: Commissioning with Cosmic Muons and First LHC Beams

In 2009, the Large Hadron Collider at CERN will collide protons with a center of mass energy of 14 TeV. ATLAS is a general purpose experiment that will allow to explore the wide potential of discovery and achieve high precision measurements. The ATLAS liquid argon calorimeters are presented, with an emphasis on their in situ commissioning using cosmic muons and their response during the first LHC single beam runs on September 2008

L’étranger : ogre ou bon Samaritain?

Les programmes de prévention s'adressant aux enfants, concernant le risque d'enlèvement oud'agression sexuellle ou phsique, reposent sur des efforts de prévention face à l'étranger. Laréalité des enfants est toute autre. L'auteur montre que la maltraitance physique et sexuelle enOntario est le fait de personnes connues de l'enfant, tout particulièrement des parents

OpenElectrophy: An Electrophysiological Data- and Analysis-Sharing Framework

Progress in experimental tools and design is allowing the acquisition of increasingly large datasets. Storage, manipulation and efficient analyses of such large amounts of data is now a primary issue. We present OpenElectrophy, an electrophysiological data- and analysis-sharing framework developed to fill this niche. It stores all experiment data and meta-data in a single central MySQL database, and provides a graphic user interface to visualize and explore the data, and a library of functions for user analysis scripting in Python. It implements multiple spike-sorting methods, and oscillation detection based on the ridge extraction methods due to Roux et al. (2007). OpenElectrophy is open source and is freely available for download at http://neuralensemble.org/trac/OpenElectrophy

Sexual abuse in Canadian Aboriginal communities : a broad review of conflicting evidence

Child sexual abuse (CSA), a prevalent problem across cultures and countries, threatens the well-being of victims, their families, and communities. Reports on the rates of CSA among Aboriginal people in Canada differ on the extent of this problem in the communities, with some studies reporting epidemic rates of sexual exploitation of Aboriginal children. Careful analysis and interpretation is required to more accurately capture the scope of CSA in Canadian Aboriginal communities. This broad review of evidence on CSA clearly shows the striking differences between adult reports of CSA experiences that occurred many years or decades ago and current cases of children and youth investigated for CSA. On one hand, after discarding misquoted research and studies conducted with at-risk populations, we find an estimate of 25–50% CSA prevalence rate in Aboriginal adults surveyed across Canada in the past 20 years. Based on the review of this literature, CSA seems to be a prevalent social problem in both Aboriginal and non- Aboriginal adults, although research indicates the former group is more at risk than the latter. On the other hand, recent cases investigated by the Canadian child protection services show CSA is a less common problem for Aboriginal children and youth (0.53 by 1000) than for their non-Aboriginal counterparts (0.62 by 1000). Given that most CSA cases, across all cultures, never come to the attention of the authorities, the striking difference between current CSA rates among children and youth and adult reports of CSA experiences raises several critical questions. Are Aboriginal children experiencing significantly lower rates of sexual abuse than their parents, or is sexual abuse being dramatically underreported both for Aboriginal and non-Aboriginal children? Exploring both sides of this problem increases our understanding of CSA in Aboriginal communities and brings critical new light to this social problem. Future directions for research are proposed to generate sound statistical data that will provide the basis for developing appropriate policies, legislation, and services for victims

Facteurs associés à la décision de recourir au Tribunal de la jeunesse lors de l’orientation des mesures de prise en charge

Parmi les décisions que les intervenants de la protection de la jeunesse ont à prendre, le recours au Tribunal de la jeunesse afin d’imposer à la famille des mesures de prise en charge représente une décision importante et lourde de conséquences tant pour l’intervenant que pour la famille. Dans ce contexte, la présente étude vise à déterminer les facteurs associés à la décision de recourir au Tribunal de la jeunesse dans les cas où la sécurité ou le développement de l’enfant ont été jugés compromis. L’échantillon comprend 2264 enfants dont les faits signalés ont été jugés fondés et la sécurité ou le développement compromis. Les variables examinées concernent les caractéristiques des enfants, des parents, de la famille, des mauvais traitements et des services reçus. Les résultats de l’analyse de régression multiple par blocs hiérarchiques montrent que la coopération des parents, la chronicité des situations (prise en charge antérieure au cours des cinq dernières années et durée des mauvais traitements/troubles de comportement), la vulnérabilité de l’enfant (jeune âge et nombre de besoins de services), la gravité des situations (abandon de l’enfant, présence de mesures d’urgence et de poursuites criminelles) de même que certains facteurs de risque familiaux (aide sociale et déménagements fréquents) sont fortement associés à la décision de recommander le recours au Tribunal de la jeunesse.Resorting to Youth Court in order to impose youth protection services on a family is one of the most important and consequential decisions that child protection workers must take. This study sought to determine the factors associated with this decision in cases where the security and development of a child are considered endangered. The sample used in the analyses comprised 2264 children for whom the events reported were considered substantiated and whose security and development were considered endangered. The variables investigated concern characteristics of the child, the parents, the family, the maltreatment suffered, and the services received. Results of hierarchical multiple regression analysis show that parental cooperation, chronicity of situations (prior use of youth protection services in past five years and duration of maltreatment/behavioural problems), child’s vulnerability (young age and number of service needs), severity of situations (abandonment of child, presence of emergency measures and criminal charges), and certain familial risk factors (social welfare and frequent changes of residence) proved strongly associated with the decision to recommend recourse to Youth Court

La mobilisation des connaissances en protection de l’enfance

La protection de l’enfance est l’un des secteurs de services qui se développent le plus rapidement au Canada. Cependant, nous en savons étonnamment peu sur l’efficacité des services offerts aux enfants maltraités et négligés. Cet article examine de nouveaux modèles de mobilisation des connaissances conçus pour soutenir l’utilisation plus systématique de la recherche dans les services sociaux. Nous commençons par discuter des limites des modèles traditionnels de diffusion des connaissances. Ensuite, nous considérons certaines des recherches qui ont été faites sur les obstacles et les facteurs facilitant l’utilisation de la recherche en santé, en éducation et dans les services sociaux. Enfin, nous présentons un modèle de mobilisation des connaissances qui est mis à l’essai et évalué dans un organisme de protection de l’enfance au Québec, décrivons les processus locaux utilisés pour affiner les six indicateurs de résultats (récurrence de la maltraitance, retards scolaires, taux de placement, déplacements d’une ressource à une autre, durée des soins et participation d’un tribunal) et concluons en présentant un exemple d’un des indicateurs retenus.Child protection is one of the fastest growing services sectors in Canada, yet we know surprisingly little about the effectiveness of services for abused and neglected children. This article examines emerging knowledge mobilization models designed to support the more systematic use of research in social services. We start by discussing the limits of traditional knowledge dissemination models. We then consider some of the research that has been done on the barriers and facilitators of research utilization in health, education and social services. Finally, we present a knowledge mobilization model that is being pilot tested and evaluated in a child welfare agency in Quebec and describe the local processes used to refine six outcome indicators (recurrence of maltreatment ; school delay ; placement rate ; moves in care ; time in care ; and court involvement) and conclude by presenting an example of one of the selected indicators.La protección de la infancia es uno de los sectores de servicios de más rápido desarrollo en Canadá. Sin embargo, es sorprendente lo poco que sabemos sobre la eficacia de los servicios que se ofrecen a los menores víctimas de maltrato o de negligencia. Este artículo examina nuevos modelos de movilización de conocimientos concebidos para apoyar un uso más sistemático de la investigación en los servicios sociales. Discutimos, primero, los límites de los modelos tradicionales de la difusión de conocimientos. A continuación, consideramos algunas investigaciones sobre los obstáculos y estímulos al uso de la investigación en los ámbitos de la salud, la educación y los servicios sociales. Finalmente, presentamos un modelo de movilización de conocimientos en etapa de práctica piloto y evaluación en una agencia de protección de la infancia en Quebec ; describimos los procesos locales utilizados para afinar seis indicadores de resultados (recurrencia del maltrato, retrasos escolares, tasa de colocación, desplazamiento de un recurso a otro, duración de cuidados y participación de un tribunal) y concluimos presentando un ejemplo de uno de los indicadores seleccionados

Extracting non-linear integrate-and-fire models from experimental data using dynamic I–V curves

The dynamic I–V curve method was recently introduced for the efficient experimental generation of reduced neuron models. The method extracts the response properties of a neuron while it is subject to a naturalistic stimulus that mimics in vivo-like fluctuating synaptic drive. The resulting history-dependent, transmembrane current is then projected onto a one-dimensional current–voltage relation that provides the basis for a tractable non-linear integrate-and-fire model. An attractive feature of the method is that it can be used in spike-triggered mode to quantify the distinct patterns of post-spike refractoriness seen in different classes of cortical neuron. The method is first illustrated using a conductance-based model and is then applied experimentally to generate reduced models of cortical layer-5 pyramidal cells and interneurons, in injected-current and injected- conductance protocols. The resulting low-dimensional neuron models—of the refractory exponential integrate-and-fire type—provide highly accurate predictions for spike-times. The method therefore provides a useful tool for the construction of tractable models and rapid experimental classification of cortical neurons