1,354,492 research outputs found
Program code for mean-field models of gamma-frequency oscillations in networks of excitatory and inhibitory neurons
No full text<p>Program code to simulate the models of the article:</p>
<p>Tahvili F and Destexhe A. A mean-field model of gamma-frequency oscillations in networks of excitatory and inhibitory neurons. Journal of Computational Neuroscience, i2024. DOI: <a href="https://doi.org/10.1007/s10827-024-00867-1" target="_blank" rel="noopener">https://doi.org/10.1007/s10827-024-00867-1</a></p>
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..
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>
State-dependent mean-field formalism to model different activity states in conductance-based networks of spiking neurons
No full textMore interest has been shown in recent years to large-scale spiking simulations of cerebral neuronal networks, coming both from the presence of high-performance computers and increasing details in experimental observations. In this context it is important to understand how population dynamics are generated by the designed parameters of the networks, which is the question addressed by mean-field theories. Despite analytic solutions for the mean-field dynamics already being proposed for current-based neurons (CUBA), a complete analytic description has not been achieved yet for more realistic neural properties, such as conductance-based (COBA) network of adaptive exponential neurons (AdEx). Here, we propose a principled approach to map a COBA on a CUBA. Such an approach provides a state-dependent approximation capable of reliably predicting the firing-rate properties of an AdEx neuron with noninstantaneous COBA integration. We also applied our theory to population dynamics, predicting the dynamical properties of the network in very different regimes, such as asynchronous irregular and synchronous irregular (slow oscillations). This result shows that a state-dependent approximation can be successfully introduced to take into account the subtle effects of COBA integration and to deal with a theory capable of correctly predicting the activity in regimes of alternating states like slow oscillations
Suppressive traveling waves shape representations of illusory motion in primary visual cortex of awake primate
No full textHow does the brain link visual stimuli across space and time? Visual illusions provide an experimental paradigm to study these processes. Whentwo stationary dots are flashed in close spatial and temporal succession,humanobservers experience a percept of apparent motion. Large spatiotemporal separation challenges the visual system to keep track of object identity along the apparent motion path, the so-called “correspondence problem.” Here, we use voltage-sensitive dye imaging in primary visual cortex (V1) of awake monkeys to show that intracortical connections within V1 can solve this issue by shaping cortical dynamics to represent the illusory motion. We find that the appearance of the second stimulus in V1 creates a systematic suppressive wave traveling toward the retinotopic representation of the first. Using a computational model, we show that the suppressive wave is the emergent property of a recurrent gain control fed by the intracortical network. This suppressive wave acts to explain away ambiguous correspondence problems and contributes to precisely encode the expected motion velocity at the surface of V1. Together, these results demonstrate that the nonlinear dynamics within retinotopic maps can shape cortical representations of illusory motion. Understanding these dynamics will shed light on how the brain links sensory stimuli across space and time, by preformatting population responses for a straightforward read-out by downstream areas
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Neuronal avalanches recorded in the awake and sleeping monkey do not show a power law but can be reproduced by a self-organized critical model
No full textPoster presentation: Self-organized critical (SOC) systems are complex dynamical systems that may express cascades of events, called avalanches [1]. The SOC state was proposed to govern brain function, because of its activity fluctuations over many orders of magnitude, its sensitivity to small input and its long term stability [2,3]. In addition, the critical state is optimal for information storage and processing [4]. Both hallmark features of SOC systems, a power law distribution f(s) for the avalanche size s and a branching parameter (bp) of unity, were found for neuronal avalanches recorded in vitro [5]. However, recordings in vivo yielded contradictory results [6]. Electrophysiological recordings in vivo only cover a small fraction of the brain, while criticality analysis assumes that the complete system is sampled. We hypothesized that spatial subsampling might influence the observed avalanche statistics. In addition, SOC models can have different connectivity, but always show a power law for f(s) and bp = 1 when fully sampled. This may not be the case under subsampling, however. Here, we wanted to know whether a state change from awake to asleep could be modeled by changing the connectivity of a SOC model without leaving the critical state. We simulated a SOC model [1] and calculated f(s) and bp obtained from sampling only the activity of a set of 4 × 4 sites, representing the electrode positions in the cortex. We compared these results with results obtained from multielectrode recordings of local field potentials (LFP) in the cortex of behaving monkeys. We calculated f(s) and bp for the LFP activity recorded while the monkey was either awake or asleep and compared these results to results obtained from two subsampled SOC model with different connectivity. f(s) and bp were very similar for both the experiments and the subsampled SOC model, but in contrast to the fully sampled model, f(s) did not show a power law and bp was smaller than unity. With increasing the distance between the sampling sites, f(s) changed from "apparently supercritical" to "apparently subcritical" distributions in both the model and the LFP data. f(s) and bp calculated from LFP recorded during awake and asleep differed. These changes could be explained by altering the connectivity in the SOC model. Our results show that subsampling can prevent the observation of the characteristic power law and bp in SOC systems, and misclassifications of critical systems as sub- or supercritical are possible. In addition, a change in f(s) and bp for different states (awake/asleep) does not necessarily imply a change from criticality to sub- or supercriticality, but can also be explained by a change in the effective connectivity of the network without leaving the critical state
Variations on the Author
No full text“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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