Neuromathématiques

Présentation et informations pratiques pour le séminaire 2016/2017 : voir ici

Organisateurs : Giovanna Citti (University of Bologna), Alain Destexhe (UNIC – CNRS), Olivier Faugeras (INRIA), Yves Fregnac (UNIC – CNRS), Jean-Pierre Nadal (CAMS – EHESS/CNRS), Jean Petitot (CAMS – EHESS), Gabriel Peyre (CEREMADE – CNRS), Alessandro Sarti (CAMS – EHESS/CNRS

Le séminaire sera coorganisé avec, et hébergé par, l’Institut européen de neurosciences théoriques (EITN), 74 Rue du Faubourg Saint-Antoine, 75012 Paris
http://www.eitn.eu/

 


  • Mardi 28 mars 2017, 14h30-16h30, salle de conférence de l’European Institute of Theoretical Neuroscience, 74, rue du Faubourg Saint-Antoine 75012, Paris.

    Boris Gutkin
    Ecole Normale Supérieure, Paris
    Dynamics of dopamine neuron firing in normal and drug-modulated conditions
    Dopaminergic neurons in the ventral tegmental area play a key role in signalling motivational information. Modulation of this signalling by drugs is also key to the development of addiction. These neurons have several firing modes ranging from periodic low frequency activity to higher frequency bursts. In vitro, intrinsically generated bursts are seen, while in vivo irregular high frequency alternates with periodic activity. Addictive drugs alter this firing patter towards high frequency bursting. In this talk i will discuss analysis of the mechanisms that lead to the various firing modes of the dopamine neurons and how addictive drugs alter them. Notably, I will present recent results on modelling effects of alcohol on dopaminergic dynamics and dopamine outflow. Here i will show how changes in the inhibitory input synchrony to the dopamine neurons may promote high frequency firing. Time permitting, I will show how inout structure to the dopamine neurons may control their excitabilty type and what that may imply for their ability to encode reward related signals.


  • Mardi 7 mars 2017, 14h30-16h30, salle de conférence de l’European Institute of Theoretical Neuroscience, 74, rue du Faubourg Saint-Antoine 75012, Paris.

    Catherine Tallon-Baudry
    Ecole Normale Supérieure, Paris
    Visceral inputs, brain dynamics & subjectivity
    Brain dynamics are usually considered to be constrained by brain-related parameters, such as anatomical connectivity and conduction delays, or by external factors, such as the stimulus to be processed. This classical point of view ignores the fact that the brain constantly monitors bodily inputs, in particular from life-supporting organs such as the heart or the stomach. I will present recent evidence that visceral inputs constrain brain dynamics, as measured with resting-state magneto-encephalography, functional MRI, or single-unit recordings, in humans. The neural monitoring of visceral inputs may play a fundamental role by generating an egocentric reference frame, from which first-person perspective, or subjectivity, can develop. I will present data showing that neural responses to heartbeats in the default-network play a functional role as they encode self-relevance in sontaneous thoughts but also predict subjective visual experience. Visceral-brain interactions might thus represent a core mechanism constraining both brain dynamics and « cold » cognitive processes.


  • Mardi 7 février 2017, 14h30-16h30, salle de conférence de l’European Institute of Theoretical Neuroscience, 74, rue du Faubourg Saint-Antoine 75012, Paris.

    Romain Veltz
    INRIA, Sophia Antipolis
    Hopf bifurcation in the mean field of a stochastic spiking neural networks
    In this work, we provide three different numerical evidences for the occurrence of a Hopf bifurcation in a recently derived mean field limit of a stochastic network of excitatory spiking neurons. The mean field limit is a challenging nonlocal nonlinear transport equation with boundary conditions.  The first evidence relies on the computation of the spectrum of the linearised equation. The second stems from the simulation of the full mean field. The third and last evidence comes from the simulation of the network for a large number of neurons. In passing, we provide a « recipe » to find such bifurcation. Finally, this work shows how the noise level impacts the transition from asynchronous activity to partial synchronisation in excitatory globally pulse-coupled networks.


  • Mardi 6 décembre 2016, 14h30-16h30, salle de conférence de l’European Institute of Theoretical Neuroscience, 74, rue du Faubourg Saint-Antoine 75012, Paris.

SEANCE ANNULEE : L’orateur Boris Gutkin ayant un ennui de santé, la séance de ce jour du séminaire du CAMS « Neuromathématiques », est annulée. En vous priant, de sa part et de la nôtre, de nous excuser pour cette annulation de dernière minute.

Boris Gutkin
Ecole Normale Supérieure, Paris
Dynamics of dopamine neuron firing in normal and drug-modulated conditions
Dopaminergic neurons in the ventral tegmental area play a key role in signalling motivational information. Modulation of this signalling by drugs is also key to the development of addiction. These neurons have several firing modes ranging from periodic low frequency activity to higher frequency bursts. In vitro, intrinsically generated bursts are seen, while in vivo irregular high frequency alternates with periodic activity. Addictive drugs alter this firing patter towards high frequency bursting. In this talk i will discuss analysis of the mechanisms that lead to the various firing modes of the dopamine neurons and how addictive drugs alter them. Notably, I will present recent results on modelling effects of alcohol on dopaminergic dynamics and dopamine outflow. Here i will show how changes in the inhibitory input synchrony to the dopamine neurons may promote high frequency firing. Time permitting, I will show how inout structure to the dopamine neurons may control their excitability type and what that may imply for their ability to encode reward related signals.
Vous pouvez retrouver l’affiche de cette séance ici


  • Mardi 8 novembre, 14h30-16h30, salle de conférence de l’European Institute of Theoretical Neuroscience, 74, rue du Faubourg Saint-Antoine 75012, Paris.

    Romain Brette
    Institut de la Vision, Paris
    Neuronal geometry and excitability
    Most theoretical studies on neural excitability have dealt with either isopotential membranes, for example the space-clamped squid axon, or homogeneous axons. However, in most vertebrate neurons, action potentials are initiated in a small region of the axon, the axonal initial segment (AIS), packed with sodium channels and placed very close to the soma. Thus there is a spatial discontinuity in channel properties and geometry (large soma, thin axon). In addition, both the length and position of the AIS can vary with activity. In this presentation, I will show how neuron and AIS geometry impact the initiation of action potentials and their backpropagation to the soma.

    Géométrie neuronale et excitabilité
    La plupart des études théoriques sur l’excitabilité neuronale ont porté sur des membranes isopotentielles, comme par example l’axone géant du calamar dans lequel une tige métallique est insérée, ou sur des axones homogènes. Cependant, dans la plupart des neurones des vertébrés, les potentiels d’action sont initiés dans une petite région de l’axone appelée le segment initial axonal (SIA), qui contient une forte densité de canaux sodiques et est placé très proche du soma. Ainsi il y a une discontinuité spatiale dans les propriétés des canaux et la géométrie (grand soma, petit axone). De plus, la position et la longueur du SIA varient avec l’activité. Dans cette présentation, je montrerai l’effet de la géométrie du neurone et du SIA sur l’initiation des potentiels d’action et leur rétropropagation au soma.

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