Astrocytic Ion Dynamics: Implications for Potassium Buffering and Liquid Flow

We review modeling of astrocyte ion dynamics with a specific focus on the implications of so-called spatial potassium buffering, where excess potassium in the extracellular space (ECS) is transported away to prevent pathological neural spiking. The recently introduced Kirchoff-Nernst-Planck (KNP) scheme for modeling ion dynamics in astrocytes (and brain tissue in general) is outlined and used to study such spatial buffering. We next describe how the ion dynamics of astrocytes may regulate microscopic liquid flow by osmotic effects and how such microscopic flow can be linked to whole-brain macroscopic flow. We thus include the key elements in a putative multiscale theory with astrocytes linking neural activity on a microscopic scale to macroscopic fluid flow.Comment: 27 pages, 7 figure

Astrocytic Mechanisms Explaining Neural-Activity-Induced Shrinkage of Extraneuronal Space

Neuronal stimulation causes ∼30% shrinkage of the extracellular space (ECS) between neurons and surrounding astrocytes in grey and white matter under experimental conditions. Despite its possible implications for a proper understanding of basic aspects of potassium clearance and astrocyte function, the phenomenon remains unexplained. Here we present a dynamic model that accounts for current experimental data related to the shrinkage phenomenon in wild-type as well as in gene knockout individuals. We find that neuronal release of potassium and uptake of sodium during stimulation, astrocyte uptake of potassium, sodium, and chloride in passive channels, action of the Na/K/ATPase pump, and osmotically driven transport of water through the astrocyte membrane together seem sufficient for generating ECS shrinkage as such. However, when taking into account ECS and astrocyte ion concentrations observed in connection with neuronal stimulation, the actions of the Na+/K+/Cl− (NKCC1) and the Na+/HCO3− (NBC) cotransporters appear to be critical determinants for achieving observed quantitative levels of ECS shrinkage. Considering the current state of knowledge, the model framework appears sufficiently detailed and constrained to guide future key experiments and pave the way for more comprehensive astroglia–neuron interaction models for normal as well as pathophysiological situations

The extractive industries and development: The resource curse at the micro, meso and macro levels

The resource curse literature has necessarily evolved in a rather fragmented way. While economists, political economists and political scientists have largely focused on the role of mineral abundance in long-term growth with the analysis largely confined to the country (macro) or regional (meso) level, anthropologists, sociologists and other social scientists have explored the development impacts of extractive industries at the community (micro) level. While this has provided a rigorous and comprehensive exploration of extractive industries and their impacts, causal factors that bridge and/or leap-frog these levels tend not to be accounted for. In this paper we examine the evolution of the literature across disciplinary lines and different levels of scale to assess the current status of resource curse debates. In so doing, we aim to explore how an integration of the various multi-scale approaches can help address the persistent problem of the resource curse

Beyond Divide and Rule : Weak Dictators, Natural Resources and Civil Conflict

We propose a model where weak rulers have incentives to let ethnically divided countries plunge in civil war. Allowing inter-group fighting reduces production - and hence the tax base - but enables the ruler to devote more resources to increasing the tax rate. This mechanism is increasingly salient with larger amounts of natural resources, especially if these are unequally distributed across ethnic groups. We validate the theoretical predictions using cross-country data, and show that our empirical results are robust to controlling for the usual determinants of civil war incidence, and to using various proxies for the ruler’s relative weakness and for the presence of natural resources.status: publishe

Climate change effects on people’s livelihood

Generally climate is defined as the long-term average weather conditions of a particular place, region, or the world. Key climate variables include surface conditions such as temperature, precipitation, and wind. The Intergovernmental Panel on Climate Change (IPCC) broadly defined climate change as any change in the state of climate which persists for extended periods, usually for decades or longer (Allwood et al. 2014). Climate change may occur due to nature’s both internal and external processes. External process involves anthropogenic emission of greenhouse gases to the atmosphere, and volcanic eruptions. The United Nations Framework Convention on Climate Change (UNFCCC) made a distinction between climate change attributable to human contribution to atmospheric composition and natural climate variability. In its Article 1, the UNFCCC defines climate change as “a change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods” (United Nations 1992, p. 7)

A Neuron-Glial Perspective for Computational Neuroscience

International audienceThere is growing excitement around glial cells, as compelling evidence point to new, previously unimaginable roles for these cells in information processing of the brain, with the potential to affect behavior and higher cognitive functions. Among their many possible functions, glial cells could be involved in practically every aspect of the brain physiology in health and disease. As a result, many investigators in the field welcome the notion of a Neuron-Glial paradigm of brain function, as opposed to Ramon y Cayal's more classical neuronal doctrine which identifies neurons as the prominent, if not the only, cells capable of a signaling role in the brain. The demonstration of a brain-wide Neuron-Glial paradigm however remains elusive and so does the notion of what neuron-glial interactions could be functionally relevant for the brain computational tasks. In this perspective, we present a selection of arguments inspired by available experimental and modeling studies with the aim to provide a biophysical and conceptual platform to computational neuroscience no longer as a mere prerogative of neuronal signaling but rather as the outcome of a complex interaction between neurons and glial cells

Doctoriales du Sophiapol, 15 avril 2015, Paris Ouest

Le laboratoire Sophiapol organise une journée d’étude dédiée aux travaux de ses doctorant-e-s. Ces doctoriales visent, d’une part, à échanger sur la diversité des travaux du laboratoire, et, d’autre part, à valoriser les problématiques transversales à la philosophie et la sociologie. À la suite du séminaire « Pratiques croisées », nous chercherons à faire dialoguer ces deux disciplines, autour de quatre axes : 1. Critique de la marchandise ; 2. Rejet de l'essentialisme ; 3. Mise en crise de l..