2,719 research outputs found
Destexhe Alain, Amérique centrale. Enjeux politiques
No full textLempérière-Roussin Annick. Destexhe Alain, Amérique centrale. Enjeux politiques. In: Vingtième Siècle, revue d'histoire, n°25, janvier-mars 1990. Dossier : le Brésil au pluriel. p. 128
Destexhe Alain, Amérique centrale. Enjeux politiques
No full textLempérière-Roussin Annick. Destexhe Alain, Amérique centrale. Enjeux politiques. In: Vingtième Siècle, revue d'histoire, n°25, janvier-mars 1990. Dossier : le Brésil au pluriel. p. 128
Amérique Centrale, enjeux politiques / Alain Destexhe
No full textCollection : Questions au XXe siècle ; 9Collection : Questions au XXe siècle ; 9Contient une table des matièresAvec mode text
Python code to simulate mouse, monkey and human brains
No full text<p>This archive contains the python codes to run the TVB-AdEx model of mouse, monkey and human brains. The models run in The Virtual Brain simulator, where AdEx mean-fields were implemented. This model reproduces two brain states, asynchronous activity similar to wakefulness, and slow-wave activiy similar to sleep and anesthesia.</p><p>The human model is described in the following papers:</p><p>Goldman, J.S., Kusch, L., Yalcinkaya, B.H., Depannemaecker, D., Nghiem, T-A., Jirsa, V. and Destexhe, A. Brain-scale emergence of slow-wave synchrony and highly responsive asynchronous states based on biologically realistic population models simulated in The Virtual Brain. bioRxiv (2020): https://www.biorxiv.org/content/10.1101/2020.12.28.424574v1</p><p>Goldman, J.S., Kusch, L., Aquilue, D., Yalcinkaya, B.H., Depannemaecker, D., Ancourt, K., Nghiem, T-A., Jirsa, V. and<br>Destexhe, A. A comprehensive neural simulation of slow-wave sleep and highly responsive wakefulness dynamics. Frontiers in Computational Neuroscience 16: 1058957, 2022. DOI: https://doi.org/10.3389/fncom.2022.1058957</p><p>The three species (human, monkey, mouse) are described in:</p><p>Goldman, J., Sacha, M., Kusch, L. and Destexhe, A. Asynchronous and slow-wave oscillatory states in connectome-based models of mouse, monkey and human cerebral cortex. Biorxiv (2023): https://www.biorxiv.org/content/10.1101/2023.08.03.551869v1</p><p>See these papers for details.</p><p>The mouse and macaque brain models were built in a very similar way.</p><p>This work was financed by the Human Brain Project, under the direction of Alain Destexhe.</p>
Biologically Realistic Mean-Field Models of Conductance-Based Networks of Spiking Neurons with Adaptation
No full textAccurate population models are needed to build very large-scale neural models, but their derivation is difficult for realistic networks of neurons, in particular when nonlinear properties are involved, such as conductance-based interactions and spike-frequency adaptation. Here, we consider such models based on networks of adaptive exponential integrate-and-fire excitatory and inhibitory neurons. Using a master equation formalism, we derive a mean-field model of such networks and compare it to the full network dynamics. The mean-field model is capable of correctly predicting the average spontaneous activity levels in asynchronous irregular regimes similar to in vivo activity. It also captures the transient temporal response of the network to complex external inputs. Finally, the mean-field model is also able to quantitatively describe regimes where high- and low-activity states alternate (up-down state dynamics), leading to slow oscillations. We conclude that such mean-field models are biologically realistic in the sense that they can capture both spontaneous and evoked activity, and they naturally appear as candidates to build very large-scale models involving multiple brain areas
Rwanda : essai sur le génocide / Alain Destexhe ; [avec la collab. de Laure Delcros]
No full textContient une table des matièresAvec mode text
Intracellular and Computational Characterization of the Intracortical Inhibitory Control of Synchronized Thalamic Inputs In Vivo
No full textContreras, Diego, Alain Destexhe, and Mircea Steriade. Intracellular and computational characterization of the intracortical inhibitory control of synchronized thalamic inputs in vivo. J. Neurophysiol. 78: 335–350, 1997. We investigated the presence and role of local inhibitory cortical control over synchronized thalamic inputs during spindle oscillations (7–14 Hz) by combining intracellular recordings of pyramidal cells in barbiturate-anesthetized cats and computational models. The recordings showed that 1) similar excitatory postsynaptic potential (EPSP)/inhibitory postsynaptic potential (IPSP) sequences occurred either during spindles or following thalamic stimulation; 2) reversed IPSPs with chloride-filled pipettes transformed spindle-related EPSP/IPSP sequences into robust bursts with spike inactivation, resembling paroxysmal depolarizing shifts during seizures; and 3) dual simultaneous impalements showed that inhibition associated with synchronized thalamic inputs is local. Computational models were based on reconstructed pyramidal cells constrained by recordings from the same cells. These models showed that the transformation of EPSP/IPSP sequences into fully developed spike bursts critically needs a relatively high density of inhibitory currents in the soma and proximal dendrites. In addition, models predict significant Ca2+transients in dendrites due to synchronized thalamic inputs. We conclude that synchronized thalamic inputs are subject to strong inhibitory control within the cortex and propose that 1) local impairment of inhibition contributes to the transformation of spindles into spike-wave-type discharges, and 2) spindle-related inputs trigger Ca2+events in cortical dendrites that may subserve plasticity phenomena during sleep.</jats:p
Mr Alain Elkann Author and Journalist Italian Republic
No full textVisit by Mr Alain Elkann Author and Journalist Italian Republi
Ionic Mechanisms Underlying Synchronized Oscillations And Propagating Waves In A Model Of Ferret Thalamic Slices
No full textthis paper, we investigated model networks of TC and RE cells, endowed with intrinsic properties and topographic connectivity specific to the thalamus. The model reproduced the propagating properties of spindle waves, in agreement with another modeling study (Golomb et al., 1996) that used simpler models of thalamic neurons (no action potentials and graded synaptic transmission). The focus of Golomb et al. model was the parameters Destexhe et al., J. Neurophysiol. 76: 2049-2070, 1996 4 that influence propagation of activity but mechanisms for the initiation and termination of spindle oscillations were not included. We investigated the hypothesis that the termination, or waning, of spindles depends on an activity-dependent process in TC cells. Based on recent experiments by Bal and McCormick (1995), we assume that the calcium-dependent upregulation of a hyperpolarization-activated current, I h , is the biophysical basis of the waning. We show that this mechanism, together with other known intrinsic and synaptic properties of the thalamic circuitry, accounts for the initiation, propagation and termination of spindle waves. We also show that the same model exhibits the patterns of oscillation observed following application of bicuculline, a GABAA receptor antagonist. This convulsant transforms spindles into a slower and more synchronized oscillations (von Krosigk et al., 1993; Bal et al., 1995a, 1995b; Kim et al., 1995), similar to the pattern seen in thalamic neurons during some types of epileptic discharges. In agreement with previous models (Destexhe and Sejnowski, 1995; Golomb et al., 1996), lateral inhibition in the RE nucleus was essential in developing such patterns of discharges. Some of the results presented here were reported previously in an abstract (Destexhe..
Mechanisms Underlying the Synchronizing Action of Corticothalamic Feedback Through Inhibition of Thalamic Relay Cells
No full text Destexhe, Alain, Diego Contreras, and Mircea Steriade. Mechanisms underlying the synchronizing action of corticothalamic feedback through inhibition of thalamic relay cells. J. Neurophysiol. 79: 999–1016, 1998. Early studies have shown that spindle oscillations are generated in the thalamus and are synchronized over wide cortical territories. More recent experiments have shown that this large-scale synchrony depends on the integrity of corticothalamic feedback. Previously proposed mechanisms emphasized exclusively intrathalamic mechanisms to generate the synchrony of these oscillations. In the present paper, we propose a cellular mechanism in which the synchrony is dependent of a mutual interaction between cortex and thalamus. This cellular mechanism is tested by computational models consisting of pyramidal cells, interneurons, thalamic reticular (RE) and thalamocortical (TC) relay cells, on the basis of voltage-clamp data on intrinsic currents and synaptic receptors present in the circuitry. The model suggests that corticothalamic feedback must operate on the thalamus mainly through excitation of GABAergic RE neurons, therefore recruiting relay cells essentially through inhibition and rebound. We provide experimental evidence for such dominant inhibition in the lateral posterior nucleus. In these conditions, the model shows that cortical discharges optimally evoked thalamic oscillations. This feature is essential to the present cellular mechanism and is also consistently observed experimentally. The model further shows that, with this type of corticothalamic feedback, cortical discharges recruited large areas of the thalamus because of the divergent cortex-to-RE and RE-to-TC axonal projections. Consequently, the thalamocortical network generated patterns of oscillations and synchrony similar to in vivo recordings. The model also emphasizes the important role of the modulation of the I h current by calcium in TC cells. This property conferred a relative refractoriness to the entire network, a feature also observed experimentally, as we show here. Further, the same property accounted for various spatiotemporal features of oscillations, such as systematic propagation after low-intensity cortical stimulation, local oscillations, and more generally, a high variability in the patterns of spontaneous oscillations, similar to in vivo recordings. We propose that the large-scale synchrony of spindle oscillations in vivo is the result of thalamocortical interactions in which the corticothalamic feedback acts predominantly through the RE nucleus. Several predictions are suggested to test the validity of this model. </jats:p
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