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 neuron

Experimental and numerical investigation of two-phase flow in a model of nanoporous medium

1.Motivation / Context 2.Fabrication and procedure 3.Two phase flow in dead end nanochannel

The Excitatory Neuronal Network of the C2 Barrel Column in Mouse Primary Somatosensory Cortex

Local microcircuits within neocortical columns form key determinants of sensory processing. Here, we investigate the excitatory synaptic neuronal network of an anatomically defined cortical column, the C2 barrel column of mouse primary somatosensory cortex. This cortical column is known to process tactile information related to the C2 whisker. Through multiple simultaneous whole-cell recordings, we quantify connectivity maps between individual excitatory neurons located across all cortical layers of the C2 barrel column. Synaptic connectivity depended strongly upon somatic laminar location of both presynaptic and postsynaptic neurons, providing definitive evidence for layer-specific signaling pathways. The strongest excitatory influence upon the cortical column was provided by presynaptic layer 4 neurons. In all layers we found rare large-amplitude synaptic connections, which are likely to contribute strongly to reliable information processing. Our data set provides the first functional description of the excitatory synaptic wiring diagram of a physiologically relevant and anatomically well-defined cortical column at single-cell resolution

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

La modernité des Fasu de Haivaro : incarner, désincarner et réincarner les relations

Cette thèse analyse la manière dont les relations de paternité, de fraternité, de conjugalité, de genre et d'altérité qui construisent l'univers de vie des Fasu de Haivaro (un village situé dans les basses-terres au nord-ouest de la Province du Golfe, en Papouasie-Nouvelle-Guinée) ont été - et sont toujours - renégociées et reconfigurées dans le contexte de leur engagement avec de multiples expressions de la modernité, et plus particulièrement avec une compagnie forestière implantée sur leur territoire. Cette recherche montre comment ces transformations entrainent un processus d'incarnation, de désincarnation et de réincarnation de ces relations.This thesis analyses ways in which the relationships of fatherhood, brotherhood, conjugality, gender and otherness that build the lifeworld of Fasu people of Haivaro (in the northwestern lowlands of Gulf Province, Papua New Guinea) have been and continue to be renegotiated and reconfigured in the context of their engagement with multiple expressions of modernity, in particular with a logging company operating on their land. I show how these transformations entail processes of embodiment, disembodiment and re-embodiment of those relations

The excitatory neuronal microcircuit of the C2 column in the mouse primary somatosensory cortex

Rodents are nocturnal animals gathering information about their surroundings by using highly sensitive detectors laid out on their snout. Like humans use their fingertips to apprehend textures, rodents use their whiskers to build a spatial representation of their environment, locate objects and discriminate fine textures. The most remarkable feature of the somatosensory whisker system consists in the isomorphic correspondence of each whisker with discrete cytoarchitectonic units in layer 4 of the primary somatosensory "barrel" cortex. These layer 4 barrels are the first step towards the integration of the sensory information within the neocortex and form the core of each cortical barrel column. To further our understanding of sensory processing, it becomes evident that studying the synaptic wiring of a specific barrel column will provide useful information. In this thesis work, we specifically investigate the excitatory wiring diagram of the C2 barrel related column. The functional location of our preferred column was mapped in vivo using intrinsic optical imaging upon C2 whisker deflection. The excitatory microcircuit of the C2 barrel column was investigated in vitro using simultaneous multiple whole-cell patch clamp recordings in the current clamp mode. We show that layer 4, through its highly recurrent and strong network, acts as the main excitatory driving force, spreading information across the entire cortical column. We demonstrate that supragranular layers are involved both in intralaminar recurrent circuits and top-down relations with postsynaptic partners in specific subjacent layers. The last relay of the excitation flow consists of the infragranular layers that integrate input from the whole column, and form the output of the cortical computation. Finally, by assessing the diversity of short-term dynamics of a subset of excitatory connections, we point out the complexity of sensory processing and the long journey remaining to unravel the synaptic mechanisms underlying sensory perception

Haivaro Fasu modernity: embodying, disembodying and re-embodying relationships

Completed under a Cotutelle arrangement between the University of Melbourne and Ecole des Hautes Etudes en Sciences Sociales© 2017 Dr. Sandrine LefortIn this thesis, I analyse ways in which relations that build the lifeworld of Fasu people of Haivaro, in the northwest lowlands of the Gulf Province of Papua New Guinea, have been and continue to be renegotiated and reconfigured in the context of their engagement with multiple expressions of modernity, in particular with a logging company operating on their land. I show how these transformations entail processes of embodiment, disembodiment and re-embodiment of those relations. The relationships that people develop with the human and non-human beings that populate their environment are diverse and context-dependent. They emerge and consolidate as people engage with that environment and where the latter changes – either abruptly or gradually – so too the relations that built their lifeworld also change. In the years before 1996, several logging and oil companies operated in the Haivaro region. Fasu people engaged with these only sporadically. In 1996, however, a logging company established a base camp 3km northeast of Haivaro and remained there until 2016. This company was operated by the Malaysian Rimbunan Hijau group (RH). Timber extraction began on the land of Haivaro people and they engaged with this company more intensely than with any other. Two kinds of influence were significant. On the one hand, Haivaro people became connected to the outside world in ways they had never previously experienced or contemplated and, on the other, their immediate physical environment underwent substantial transformations such that, in some ways, it became foreign to them. These changes have had – and continue to have – impacts on the ways Haivaro people understand their relationships to the land, to their human and non-human neighbours and to the wider world. These relationships are integral to the ways in which Haivaro Fasu construct their identity and, as these relationships are renegotiated, so too identity is reconfigured. The relationships of fatherhood, brotherhood, conjugality, gender and otherness that are the focus of this study were deeply associated with the representations people at Haivaro had of bodily substances. In that sense, they were deeply embodied. In the modern context, a greater emphasis has been put on the performance of specific forms of reciprocity in creating and maintaining these relations. In some ways, they have been partly dis-embodied. Concurrently, new or modified forms of relations appeared that people at Haivaro attempted to integrate – to tame – by re-embodying them. In this thesis, I discuss such processes and their implications for ways in which Haivaro people now engage with the world

Layer-Dependent Short-Term Synaptic Plasticity Between Excitatory Neurons in the C2 Barrel Column of Mouse Primary Somatosensory Cortex

Neurons process information through spatiotemporal integration of synaptic input. Synaptic transmission between any given pair of neurons is typically a dynamic process with presynaptic action potentials(APs) evoking depressing or facilitating postsynaptic potentials when presynaptic APs occur within hundreds of milliseconds of each other. In order to understand neocortical function, it is therefore important to investigate such short-term synaptic plasticity at synapses between different types of neocortical neurons. Here, we examine short-term synaptic dynamics between excitatory neurons in different layers of the mouse C2 barrel column through in vitro whole-cell recordings. We find layer-dependent short-term plasticity, with depression being dominant at many synaptic connections. Interestingly, however, presynaptic layer 2 neurons predominantly give rise to facilitating excitatory synaptic output at short interspike intervals of 10 and 30 ms. Previous studies have found prominent burst firing of excitatory neurons in supragranular layers of awake mice. The facilitation we observed in the synaptic output of layer 2 may, therefore, be functionally relevant, possibly serving to enhance the postsynaptic impact of burst firing

Layer-Dependent Short-Term Synaptic Plasticity Between Excitatory Neurons in the C2 Barrel Column of Mouse Primary Somatosensory Cortex

Neurons process information through spatiotemporal integration of synaptic input. Synaptic transmission between any given pair of neurons is typically a dynamic process with presynaptic action potentials (APs) evoking depressing or facilitating postsynaptic potentials when presynaptic APs occur within hundreds of milliseconds of each other. In order to understand neocortical function, it is therefore important to investigate such short-term synaptic plasticity at synapses between different types of neocortical neurons. Here, we examine short-term synaptic dynamics between excitatory neurons in different layers of the mouse C2 barrel column through in vitro whole-cell recordings. We find layer-dependent short-term plasticity, with depression being dominant at many synaptic connections. Interestingly, however, presynaptic layer 2 neurons predominantly give rise to facilitating excitatory synaptic output at short interspike intervals of 10 and 30 ms. Previous studies have found prominent burst firing of excitatory neurons in supragranular layers of awake mice. The facilitation we observed in the synaptic output of layer 2 may, therefore, be functionally relevant, possibly serving to enhance the postsynaptic impact of burst firing