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51. Model-guided control of hippocampal discharges by local direct current stimulation

Author

Mina, Faten, Modolo, Julien, Recher, Fanny, Dieuset, Gabriel, Biraben, Arnaud, Benquet, Pascal, Wendling, Fabrice, Laboratoire Traitement du Signal et de l'Image (LTSI), Université de Rennes (UR)-Institut National de la Santé et de la Recherche Médicale (INSERM), Service de neurologie [Rennes], Université de Rennes (UR), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut National de la Santé et de la Recherche Médicale (INSERM), and Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)

Subjects
Science, Models, Neurological, Action Potentials, Signal Processing, Computer-Assisted, Hippocampus, [INFO.INFO-MO]Computer Science [cs]/Modeling and Simulation, Electric Stimulation, Article, Mice, Animals, Medicine, Computer Simulation, [SDV.IB]Life Sciences [q-bio]/Bioengineering, Electrodes, [SPI.SIGNAL]Engineering Sciences [physics]/Signal and Image processing, Probability
Abstract

International audience; Neurostimulation is an emerging treatment for drug-resistant epilepsies when surgery is contraindicated. Recent clinical results demonstrate significant seizure frequency reduction in epileptic patients, however the mechanisms underlying this therapeutic effect are largely unknown. This study aimed at gaining insights into local direct current stimulation (LDCS) effects on hyperexcitable tissue, by i) analyzing the impact of electrical currents locally applied on epileptogenic brain regions, and ii) characterizing currents achieving an "anti-epileptic" effect (excitability reduction). First, a neural mass model of hippocampal circuits was extended to accurately reproduce the features of hippocampal paroxysmal discharges (HPD) observed in a mouse model of epilepsy. Second, model predictions regarding current intensity and stimulation polarity were confronted to in vivo mice recordings during LDCS (n = 8). The neural mass model was able to generate realistic hippocampal discharges. Simulation of LDCS in the model pointed at a significant decrease of simulated HPD (in duration and occurrence rate, not in amplitude) for cathodal stimulation, which was successfully verified experimentally in epileptic mice. Despite the simplicity of our stimulation protocol, these results contribute to a better understanding of clinical benefits observed in epileptic patients with implanted neurostimulators. Our results also provide further support for model-guided design of neuromodulation therapy.

Published
2017

55. Dense-EEG source connectivity and dynamics of functional brain networks

Author

Hassan, Mahmoud, Dufor, Olivier, Mheich, Ahmad, Biraben, Arnaud, Berrou, Claude, Benquet, Pascal, Wendling, Fabrice, Laboratoire Traitement du Signal et de l'Image ( LTSI ), Université de Rennes 1 ( UR1 ), Université de Rennes ( UNIV-RENNES ) -Université de Rennes ( UNIV-RENNES ) -Institut National de la Santé et de la Recherche Médicale ( INSERM ), Département Electronique ( ELEC ), Université européenne de Bretagne ( UEB ) -Télécom Bretagne-Institut Mines-Télécom [Paris], Lab-STICC_TB_CACS_IAS, Laboratoire des sciences et techniques de l'information, de la communication et de la connaissance ( Lab-STICC ), École Nationale d'Ingénieurs de Brest ( ENIB ) -Université de Bretagne Sud ( UBS ) -Université de Brest ( UBO ) -Télécom Bretagne-Institut Brestois du Numérique et des Mathématiques ( IBNM ), Université de Brest ( UBO ) -Université européenne de Bretagne ( UEB ) -ENSTA Bretagne-Institut Mines-Télécom [Paris]-Centre National de la Recherche Scientifique ( CNRS ) -École Nationale d'Ingénieurs de Brest ( ENIB ) -Université de Bretagne Sud ( UBS ) -Université de Brest ( UBO ) -Télécom Bretagne-Institut Brestois du Numérique et des Mathématiques ( IBNM ), Université de Brest ( UBO ) -Université européenne de Bretagne ( UEB ) -ENSTA Bretagne-Institut Mines-Télécom [Paris]-Centre National de la Recherche Scientifique ( CNRS ), Service de Neurologie [Rennes], Université de Rennes ( UNIV-RENNES ) -Université de Rennes ( UNIV-RENNES ) -Hôpital Pontchaillou-CHU Pontchaillou [Rennes], ANR-10-LABX-07-01,labex Cominlabs,Laboratoire d'excellence CominLabs ( 2013 ), European Project : 290901,EC:FP7:ERC,ERC-2011-ADG_20110209,NEUCOD ( 2012 ), Laboratoire Traitement du Signal et de l'Image (LTSI), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut National de la Santé et de la Recherche Médicale (INSERM), Département Electronique (ELEC), Université européenne de Bretagne - European University of Brittany (UEB)-Télécom Bretagne-Institut Mines-Télécom [Paris] (IMT), Laboratoire des sciences et techniques de l'information, de la communication et de la connaissance (Lab-STICC), École Nationale d'Ingénieurs de Brest (ENIB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Télécom Bretagne-Institut Brestois du Numérique et des Mathématiques (IBNM), Université de Brest (UBO)-Université européenne de Bretagne - European University of Brittany (UEB)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS)-École Nationale d'Ingénieurs de Brest (ENIB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Télécom Bretagne-Institut Brestois du Numérique et des Mathématiques (IBNM), Université de Brest (UBO)-Université européenne de Bretagne - European University of Brittany (UEB)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS), Service de Neurologie [Rennes] = Neurology [Rennes], CHU Pontchaillou [Rennes], ANR-10-LABX-0007,COMIN Labs,Digital Communication and Information Sciences for the Future Internet(2010), European Project: 290901,EC:FP7:ERC,ERC-2011-ADG_20110209,NEUCOD(2012), Hassan, Mahmoud, Digital Communication and Information Sciences for the Future Internet - - COMIN Labs2010 - ANR-10-LABX-0007 - LABX - VALID, Neural coding, specification, design and test of message passing neural machines - NEUCOD - - EC:FP7:ERC2012-02-01 - 2017-01-31 - 290901 - VALID, Université de Rennes (UR)-Institut National de la Santé et de la Recherche Médicale (INSERM), Université européenne de Bretagne - European University of Brittany (UEB)-École Nationale d'Ingénieurs de Brest (ENIB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Télécom Bretagne-Institut Brestois du Numérique et des Mathématiques (IBNM), Université de Brest (UBO)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS)-Université européenne de Bretagne - European University of Brittany (UEB)-École Nationale d'Ingénieurs de Brest (ENIB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Télécom Bretagne-Institut Brestois du Numérique et des Mathématiques (IBNM), and Université de Brest (UBO)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDV.IB] Life Sciences [q-bio]/Bioengineering, [SDV.IB]Life Sciences [q-bio]/Bioengineering, [ SPI.SIGNAL ] Engineering Sciences [physics]/Signal and Image processing, [ SDV.IB ] Life Sciences [q-bio]/Bioengineering, [SPI.SIGNAL]Engineering Sciences [physics]/Signal and Image processing, [SPI.SIGNAL] Engineering Sciences [physics]/Signal and Image processing
Abstract

National audience; Le traitement l'information par le cerveau est un processus dynamique qui met en jeu une réorganisation rapide des réseaux cérébraux fonctionnels, sur une échelle de temps très courte (< seconde). Le suivi de la dynamique spatio-temporelle de ces réseaux sur cette durée courte est une question non résolue. Nous abordons ce problème en utilisant des signaux électroencéphalographiques à haute résolution spatiale (EEG-hr, 256 électrodes), enregistrées lors d'une tâche de dénomination d'objets. La méthode proposée consiste à : (i) résoudre le problème inverse de l'EEG qui est mal posé (nombre des sources >> nombre d'électrodes), (ii) estimer les dépendances statistiques (connectivité fonctionnelle) entre les sources reconstruites , (iii) caractériser les réseaux identifiés (sous forme des noeuds connectés par des liens formant un graphe) par des analyses basées sur la théorie des graphes et (vi) segmenter, dans le temps, le processus cognitif sous la forme d'une séquence d'états de connectivité fonctionnelle (fcSs : 'functional connectivity states'). Les résultats montrent qu'un traitement approprié du signal EEG permet d'identifier une dynamique spatio-temporelle dans les réseaux fonctionnels mis en jeu durant la tâche avec une excellente résolution temporelle (de l'ordre de la ms) et spatiale (~ 1000 régions d'intérêt). Cette dynamique correspond à une séquence de six fcSs (durée : 30 ms à 160 ms) caractérisés par une corrélation de phase significative des oscillations gamma (30-45 Hz). Des transitions rapides entre ces fcS sont observées et les réseaux associés à chaque fcS se recouvrent partiellement. Ces réseaux s'instancient sur des régions cérébrales pertinentes par rapport à la tâche de dénomination d'objets, depuis la perception de l'image jusqu'à l'articulation du nom. La méthode proposée ouvre de nombreuses perspectives quant à l'identification, à partir des données d'EEG de scalp, de réseaux cérébraux mis en jeu transitoirement lors d'activités cognitives. Abstract-The information processing in the human brain is a dynamic process that involves a rapid reorganization of functional brain networks, in a very short time scale (> number of electrodes), (ii) estimating the statistical dependencies (functional connectivity) between reconstructed sources (iii) characterizing the identified networks (in the form of nodes connected by edges forming a graph) by graph theory based analysis and (vi) segmenting, in time, the cognitive process as a sequence of functional connectivity states (fcSs). The results show that appropriate processing of the EEG signals can reveal the spatiotemporal dynamics of functional brain networks involved in the task with excellent temporal (on the order of ms) and spatial (~ 1000 regions of interest) resolution. This corresponds to a dynamic sequence of six fcSs (duration: 30 ms to 160 ms) with significant gamma phase synchronization (30-45 Hz). Rapid transitions between these fcS are observed and the networks associated with each fcS partially overlap. These networks disclose relevant brain regions related to picture naming task, from the perception of the image until the naming. The proposed method offers many opportunities in the identification, from the EEG data, of brain networks involved in cognitive activities.

Published
2015

56. Quantitative analysis and EEG markers of KCNT1 epilepsy of infancy with migrating focal seizures.

Author

Kuchenbuch, Mathieu, Milh, Matthieu, Villeneuve, Nathalie, Chemaly, Nicole, Nabbout, Rima, Kaminska, Anna, Barcia, Giulia, Benquet, Pascal, Modolo, Julien, Wendling, Fabrice, Roubertie, Agathe, Carme, Emilie, Saint Martin, Anne, Hirsch, Edouard, Dubois, Fanny, Laroche, Cécile, and Sauleau, Paul

Abstract

Summary: Objective: We aimed to characterize epilepsy of infancy with migrating focal seizures (EIMFS), a rare, severe early onset developmental epilepsy related to KCNT1 mutation, and to define specific electroencephalography (EEG) markers using EEG quantitative analysis. The ultimate goal would be to improve early diagnosis and to better understand seizure onset and propagation of EIMFS as compared to other early onset developmental epilepsy. Methods: EEG of 7 EIMFS patients with KCNT1 mutations (115 seizures) and 17 patients with other early onset epilepsies (30 seizures) was included in this study. After detection of seizure onset and termination, spatiotemporal characteristics were quantified. Seizure propagation dynamics were analyzed using chronograms and phase coherence. Results: In patients with EIMFS, seizures started and were localized predominantly in temporal and occipital areas, and evolved with a stable frequency (4‐10 Hz). Inter‐ and intrahemispheric migrations were present in 60% of EIMFS seizures with high intraindividual reproducibility of temporospatial dynamics. Interhemispheric migrating seizures spread in 71% from temporal or occipital channels to the homologous contralateral ones, whereas intrahemispheric seizures involved mainly frontotemporal, temporal, and occipital channels. Causality links were present between ictal activities detected under different channels during migrating seizures. Finally, time delay index (based on delays between the different ictal onsets) and phase correlation index (based on coherence of ictal activities) allowed discrimination of EIMFS and non‐EIMFS seizures with a specificity of 91.2% and a sensitivity of 84.4%. Significance: We showed that the migrating pattern in EIMFS is not a random process, as suggested previously, and that it is a particular propagation pattern that follows the classical propagation pathways. It is notable that this study reveals specific EEG markers (time delay and phase correlation) accessible to visual evaluation, which will improve EIMFS diagnosis. [ABSTRACT FROM AUTHOR]

Published
2019
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57. [Transient brain ischemia: NMDA receptor modulation and delayed neuronal death.]

Author

Benquet, Pascal, E Gee, Christine, Gerber, Urs, Interactions cellulaires et moléculaires (ICM), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), University of Zurich, Benquet, Pascal, and Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Neurons, N-Methylaspartate, 10242 Brain Research Institute, Cell Death, nervous system, 1300 General Biochemistry, Genetics and Molecular Biology, Ischemic Attack, Transient, [SDV.NEU.NB]Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC]/Neurobiology, [SDV.MHEP.PHY]Life Sciences [q-bio]/Human health and pathology/Tissues and Organs [q-bio.TO], 570 Life sciences, biology, Humans, 610 Medicine & health, Receptors, N-Methyl-D-Aspartate
Abstract

International audience; Transient global ischemia induces delayed neuronal death in certain cell types and brain regions while sparing cells in other areas. A key process through which oxygen-glucose deprivation triggers cell death is the excessive accumulation of the neurotransmitter glutamate leading to over excitation of neurons. In certain neurons this increase in glutamate will potentiate the NMDA type of glutamate receptor, which can then initiate cell death. This review provides an update of the neurophysiological, cellular and molecular mechanisms inducing post-ischemic plasticity of NMDA receptors, focusing on the sensitive CA1 pyramidal neurons in the hippocampus as compared to the relatively resistant neighboring CA3 neurons. Both a change in the equilibrium between protein tyrosine kinases/phosphatases and an increased density of surface NMDA receptors in response to ischemia may explain the selective vulnerability of specific cell types. Implications for the treatment of stroke and reasons for the failures of human clinical trials utilizing NMDA receptor antagonists are also discussed. double dagger.

Published
2008

60. Physiological effects of low-magnitude electric fields on brain activity: Advances from in vitro, in vivoand in silicomodels

Author

Modolo, Julien, Denoyer, Yves, Wendling, Fabrice, and Benquet, Pascal

Abstract

While electrical stimulation of brain tissue has been thoroughly investigated over the last decades, ongoing questions remain regarding the neurophysiological effects of low-level electric fields (on the order of 1 V/m) on brain activity. Electric fields at such levels are, for example, induced by transcranial direct/alternating current stimulation (tDCS/tACS). Action potentials can be indeed elicited when applied (supra-threshold) electric fields are in the 10–100 V/m range, while lower (sub-threshold) electric fields result in more limited and subtler membrane polarization effects. In this review, we address the question of the mechanisms underlying the immediate effects (also referred to as acute, concurrent or short-term) and the lasting effects (also referred to as long-term or after-effects) of low-level electric fields on brain tissue. We review recent evidence at the in vitroand in vivo(animal and human) level, and also present mechanistic insights gained from in silicomodels, which are still few but have received increased attention over the recent past years. We highlight the convergent evidence towards potential mechanisms, and also discuss discrepancies between in vitrostudies and human tDCS/tACS studies that require further investigation to bridge the gap between the single-cell and large-scale network level. Possible novel avenues of research are discussed.

Published
2018
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61. A mixed-effects spatio-temporal model to assess the joint effects of ageing and Alzheimer's disease in gray matter volume

Author

Ospina, Juan David, Benquet, Pascal, Correa, Juan Carlos, Acosta, Oscar, Laboratoire Traitement du Signal et de l'Image (LTSI), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut National de la Santé et de la Recherche Médicale (INSERM), Universidad Nacional de Colombia (COLOMBIA), Universidad Nacional de Colombia [Bogotà] (UNAL), Alzheimer's Disease Neuroimaging Initiative, Le Corre, Morgane, and Université de Rennes (UR)-Institut National de la Santé et de la Recherche Médicale (INSERM)

Subjects
[SDV.IB] Life Sciences [q-bio]/Bioengineering, [SDV.IB]Life Sciences [q-bio]/Bioengineering
Abstract

International audience; The decrease in volume of gray matter (GM) has already been recognized as characteristic of Alzheimer's disease (AD) and of its progression. However the mechanism underlying this phenomenon and its interaction with the ageing process remains a subject of current research. This paper presents a mixed-effects spatio-temporal model to assess the evolution in GM volume in non-AD and AD patients. This model highlights the different spatio-temporal patterns of GM evolution in healthy elderly (HE) and AD patients, which appear to be consistent with previous studies concerning GM evolution.

Published
2012

62. A Mesoscopic Biophysical Model for Multimodal Brain Activity Data

Author

Blanchard, Solenna, Benali, H., Benquet, Pascal, Ivanov, A., Bénar, C.-G., Wendling, Fabrice, Le Corre, Morgane, Laboratoire Traitement du Signal et de l'Image (LTSI), Université de Rennes (UR)-Institut National de la Santé et de la Recherche Médicale (INSERM), Université de Rennes 1 (UR1), and Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut National de la Santé et de la Recherche Médicale (INSERM)

Subjects
[SDV.IB] Life Sciences [q-bio]/Bioengineering, [SDV.IB]Life Sciences [q-bio]/Bioengineering, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2012

63. Astrocytes and endocannabinoids involvment in the maintenance of epileptiform activity in the hippocampus

Author

Benquet, Pascal, Coiret, G., Tiaho, François, Gerber, U., Interactions cellulaires et moléculaires (ICM), Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS), Brain Reserach Institute (BRI), Universität Zürich [Zürich] = University of Zurich (UZH), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), and De Villemeur, Hervé

Subjects
[SDV.NEU]Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC], [SDV.NEU] Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC], ComputingMethodologies_GENERAL
Abstract

Poster

Published
2010

64. Future of Seizure Prediction and Intervention

Author

Nagaraj, Vivek, primary, Lee, Steven T., additional, Krook-Magnuson, Esther, additional, Soltesz, Ivan, additional, Benquet, Pascal, additional, Irazoqui, Pedro P., additional, and Netoff, Theoden I., additional

Published
2015
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66. Aromatase B radial glial progenitors: the key to brain plasticity in fish?

Author

Diotel, Nicolas, Vaillant, Colette, Pellegrini, Elisabeth, Anglade, Isabelle, Benquet, Pascal, Kah, Olivier, Interactions cellulaires et moléculaires (ICM), Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), and Brébion, Alice

Subjects
[SDV] Life Sciences [q-bio], [SDV]Life Sciences [q-bio]
Published
2010

67. In vivo imaging and electrical characterization of dividing radial glial cells in the brain of zebrafish

Author

Benquet, Pascal, Pellegrini, Elisabeth, Diotel, Nicolas, Vaillant, Colette, Chung, B. C., Tong, S. K., Senger, Fabrice, Kah, Olivier, Interactions cellulaires et moléculaires (ICM), Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS), Institute of Molecular Biology (IMB Sinica), Academia Sinica, Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), and De Villemeur, Hervé

Subjects
[SDV.BBM.BM]Life Sciences [q-bio]/Biochemistry, Molecular Biology/Molecular biology, [SDV.BDLR]Life Sciences [q-bio]/Reproductive Biology, [SDV.NEU]Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC], [SDV.NEU] Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC], ComputingMethodologies_GENERAL, [SDV.BBM.BM] Life Sciences [q-bio]/Biochemistry, Molecular Biology/Molecular biology, [SDV.BDLR] Life Sciences [q-bio]/Reproductive Biology
Abstract

Poster

Published
2009

68. Neuron-astrocyte interactions during epileptiform activity in the rat hippocampus in vitro

Author

Coiret, G., Gerber, U., Tiaho, François, Benquet, Pascal, Interactions cellulaires et moléculaires (ICM), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), De Villemeur, Hervé, and Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDV.NEU]Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC], [SDV.NEU] Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC]
Abstract

Poster 331.7 présenté le 19 octobre par P. Benquet

Published
2009

69. Multiplex in vivo characterization of transgenic Xenopus laevis tadpoles with two-photon microscopy

Author

Recher, Gaëlle, L'Hostis-Guidet, Anne, D'Amico, Laure-Anne, Coumailleau, Pascal, Guillet, Brigitte, Bonnec, Georgette, Rouède, Denis, Schaub, Emmanuel, Senger, Fabrice, Madigou, Thierry, Benquet, Pascal, Boujard, Daniel, Tiaho, François, De Villemeur, Hervé, Interactions cellulaires et moléculaires (ICM), Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS), Institut de Physique de Rennes (IPR), Université de Rennes 1 (UR1), and Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDV.BBM.BP]Life Sciences [q-bio]/Biochemistry, Molecular Biology/Biophysics, [SDV.GEN.GA]Life Sciences [q-bio]/Genetics/Animal genetics, stomatognathic diseases, [SDV.BDD.EO]Life Sciences [q-bio]/Development Biology/Embryology and Organogenesis, InformationSystems_MODELSANDPRINCIPLES, ComputingMilieux_THECOMPUTINGPROFESSION, GeneralLiterature_INTRODUCTORYANDSURVEY, ComputingMilieux_COMPUTERSANDEDUCATION, [SDV.BDD.EO] Life Sciences [q-bio]/Development Biology/Embryology and Organogenesis, [SDV.BBM.BP] Life Sciences [q-bio]/Biochemistry, Molecular Biology/Biophysics, [SDV.BBM.BM]Life Sciences [q-bio]/Biochemistry, Molecular Biology/Molecular biology, [SDV.GEN.GA] Life Sciences [q-bio]/Genetics/Animal genetics, [SDV.BBM.BM] Life Sciences [q-bio]/Biochemistry, Molecular Biology/Molecular biology
Abstract

Communication orale

Published
2009

70. Involvement of neuro-astrocytic interactions in epileptiform activity in the rat hippocampus in vitro

Author

Coiret, G., Gerber, U., Tiaho, François, Benquet, Pascal, Brain Reserach Institute (BRI), Universität Zürich [Zürich] = University of Zurich (UZH), Interactions cellulaires et moléculaires (ICM), Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), and De Villemeur, Hervé

Subjects
[SDV.NEU]Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC], [SDV.NEU] Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC], ComputingMethodologies_GENERAL
Abstract

Poster

Published
2008

71. Transgenic Xenopus laevis and two-photon microscopy to study neurogenesis

Author

Recher, Gaëlle, Benquet, Pascal, L'Hostis-Guidet, Anne, Madigou, Thierry, Boujard, Daniel, Tiaho, François, Interactions cellulaires et moléculaires (ICM), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), De Villemeur, Hervé, and Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDV.BBM.BP]Life Sciences [q-bio]/Biochemistry, Molecular Biology/Biophysics, [SDV.GEN.GA]Life Sciences [q-bio]/Genetics/Animal genetics, [SDV.BDD.EO]Life Sciences [q-bio]/Development Biology/Embryology and Organogenesis, [SDV.BDD.EO] Life Sciences [q-bio]/Development Biology/Embryology and Organogenesis, [SDV.BBM.BP] Life Sciences [q-bio]/Biochemistry, Molecular Biology/Biophysics, [SDV.BBM.BM]Life Sciences [q-bio]/Biochemistry, Molecular Biology/Molecular biology, [SDV.GEN.GA] Life Sciences [q-bio]/Genetics/Animal genetics, ComputingMethodologies_GENERAL, [SDV.BBM.BM] Life Sciences [q-bio]/Biochemistry, Molecular Biology/Molecular biology
Abstract

Poster

Published
2008

72. Spatio-temporal cellular expression of NeuroD and related cells properties in transgenic /Xenopus laevis/ tadpoles and froglets

Author

Recher, Gaëlle, L'Hostis-Guidet, Anne, Guillet, Brigitte, Benquet, Pascal, Tiaho, François, Boujard, Daniel, Interactions cellulaires et moléculaires (ICM), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS), and De Villemeur, Hervé

Subjects
[SDV.BBM.BP]Life Sciences [q-bio]/Biochemistry, Molecular Biology/Biophysics, [SDV.GEN.GA]Life Sciences [q-bio]/Genetics/Animal genetics, [SDV.BDD.EO]Life Sciences [q-bio]/Development Biology/Embryology and Organogenesis, [SDV.BDD.EO] Life Sciences [q-bio]/Development Biology/Embryology and Organogenesis, [SDV.BBM.BP] Life Sciences [q-bio]/Biochemistry, Molecular Biology/Biophysics, [SDV.BBM.BM]Life Sciences [q-bio]/Biochemistry, Molecular Biology/Molecular biology, [SDV.GEN.GA] Life Sciences [q-bio]/Genetics/Animal genetics, ComputingMethodologies_GENERAL, [SDV.BBM.BM] Life Sciences [q-bio]/Biochemistry, Molecular Biology/Molecular biology
Abstract

Poster

Published
2008

73. Transition from normal to epileptic activity in CA1 pyramidal cell model

Author

Demont, Sophie, Benquet, Pascal, Wendling, Fabrice, Laboratoire Traitement du Signal et de l'Image (LTSI), Université de Rennes (UR)-Institut National de la Santé et de la Recherche Médicale (INSERM), Interactions cellulaires et moléculaires (ICM), Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut National de la Santé et de la Recherche Médicale (INSERM), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), and De Villemeur, Hervé

Subjects
[SDV.NEU]Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC], [SDV.NEU] Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC], ComputingMethodologies_GENERAL
Abstract

Poster

Published
2008

74. Ischémie cérébrale : modulation des récepteurs NMDA et mort neuronale retardée

Author

Benquet, Pascal, Interactions cellulaires et moléculaires (ICM), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS), and De Villemeur, Hervé

Subjects
[SDV.NEU]Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC], [SDV.NEU] Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC]
Published
2007

75. Release of glutamate produces calcium transients in Xenopus laevis NeuroD expressing neuroblasts

Author

Recher, Gaëlle, Benquet, Pascal, L'Hostis-Guidet, Anne, Madigou, Thierry, Boujard, Daniel, Tiaho, François, De Villemeur, Hervé, Interactions cellulaires et moléculaires (ICM), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), and Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS)

Subjects
animal structures, nervous system, embryonic structures, [SDV.NEU]Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC], sense organs, [SDV.NEU] Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC]
Abstract

Poster; NeuroD is a proneural gene for primary and secondary neurogenesis. Recent advances in transgenesis technique have allowed identification of posmitotic living neuroblasts and it appeared that their electrical activity (ionic channels and neurotransmitter receptors) is a prerequisite for they proper migration and differentiation. Our laboratory has developed a transgenic xenopus line which expresses EGFP under the control of NeuroD promoter and this gave us the possibility to study the properties of EGFP expressing living neuroblasts, either in the context of living tadpole or in brain slices. The spatial expression pattern of NeuroD+ cells in vivo was found to decrease from whole brain expression at stage 40 to restricted areas at stage 48 (olfactory bulb, pallium, optic tectum, cerebellum, rhombencephalon). No colocalization of EGFP and the glial marker SR-101 was found, confirming that EGFP cells are not astrocytes. Some functional properties of these cells were determined using time laps calcium imaging of acute brain slices with confocal microscopy. NeuroD+ cells were found to exhibit more calcium transients when Mg2+ was removed from the medium, and this effect is reversed by addition of APV (a NMDA receptor antagonist). Moreover, NeuroD+ cells respond more to bath application of glutamate or NMDA than NeuroD- cells. Taken together, these results suggest that a spontaneous release of glutamate produce calcium transients in NeuroD+ cells, and that activity is triggered by NMDA receptors.

Published
2007

76. Network Oscillations in organotypic slice cultures

Author

Benquet, Pascal, Gee, C.E, Gerber, U., De Villemeur, Hervé, Interactions cellulaires et moléculaires (ICM), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), and Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS)

Subjects
nervous system, [SDV.NEU]Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC], ComputingMethodologies_GENERAL, [SDV.NEU] Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC]
Abstract

Poster; Rhythmic network activity at theta frequencies is a hallmark of a functioning hippocampus. In organotypic hippocampal slice cultures, low quantities of the metabotropic receptor agonists methacholine (~20 nM) or DHPG (~100 nM) are able to activate the network and induce theta oscillations. Similar activity is also induced in the CA3 region during transient oxygen-glucose deprivation (OGD). In whole-cell voltageclamp recordings, we find that the activity induced by OGD depends on the network as it is blocked by TTX, by the glutamatergic antagonist NBQX, or by the GABAergic antagonist picrotoxin. Preventing NMDA receptor activation with CPP did not, however, prevent the network activity. Selectively blocking AMPA receptors with either SYM2206 or GYKI52466 led to a profound alteration in the OGD-induced activity marked by frequent repetitive giant depolarizing currents. The gap junction blocker mefloquine reduced rhythmicity as did the GluR6 antagonist UBP302. These data, together with the observation that the activity is dominated by inhibitory events, suggest that the interneuron network is important for the generation of these oscillations. Bulk-loading with Ca2+ indicators and high speed Ca2+ imaging with a CCD camera revealed rhythmic fluctuations in the neuropil in response to 100 nM DHPG, presumably reflecting action potentialinduced calcium signals in labeled axons and terminals. In addition, two classes of Ca2+ signal were resolved in single cells. Slow wave-like responses occurred in some cells, presumably astrocytes, whereas in other cells that are presumably neurons, much faster spike-like events were observed whose peaks corresponded with the peaks in the neuropil signal. Based on their location in the slice, many of these cells are likely to be interneurons. Further work is aimed at identifying the cell types and their roles in generating and synchronizing the network activity.

Published
2007

77. Building epileptiform activity from hippocampus cells models

Author

Demont, Sophie, Benquet, Pascal, Wendling, Fabrice, De Villemeur, Hervé, Laboratoire Traitement du Signal et de l'Image (LTSI), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut National de la Santé et de la Recherche Médicale (INSERM), Interactions cellulaires et moléculaires (ICM), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), Université de Rennes (UR)-Institut National de la Santé et de la Recherche Médicale (INSERM), and Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDV.NEU]Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC], [SDV.NEU] Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC]
Abstract

Poster; Epilepsy is one of the most common neurological disorders, characterized by recurrent seizures. The pathophysiological interpretation of specific electrophysiologicial patterns recorded during interictal (outside seizures) or ictal (seizures) periods is of crucial importance as electrophysiologicial recording (scalp and intracerebral EEG) remains one of the gold standard technique in the investigation of drug-resistant epilepsy. The general objective of this work is to bridge between single unit activity (cellular level) and field activity (network level) using computational modeling. We currently focus on the role of the hippocampus (CA1 and CA3 sub-fields) often involved in Temporal Lobe Epilepsy. Our approach is based on the use of “minimal” but still biologically-relevant neuron models. For pyramidal cells of CA1, we elaborated a two-compartment model by reducing a more complex model [Poirazi and al, 2003]. This simplification consists in two steps. First, we retained the main active voltage gated currents (related to sodium, potassium and calcium channels) known to be involved in transitions from single spike (normal) to burst activity (epileptic).This selection was performed on the basis of a literature review about experimental models of epilepsy. Second, we reduced the number of compartments from 183 to 2 (somatic and dendritic). For CA3 pyramidal cells, we implemented the reduced Traub model [Traub et al, 1991] proposed by Pinsky and Rinzel [Pinsky and Rinzel, 1994]. This two-compartment representation uses the sodium and potassium delayed rectifier current in the soma and the calcium and potassium calcium-activated current into a dendrite-like compartment. Finally, as far as interneurons are concerned, only basket and OLM cells are considered [Wang and al, 1996, 2002]. These cells are represented using single-compartment models. Network simulations use AMPA, NMDA and GABA synapses. A comparison with experimental data (animal models) allowed us to evaluate our computational models. Results showed that the reduction still preserve electrophysiologically-relevant features. In particular, blocking A type potassium current leads the CA1 pyramidal model to switch from normal to burst activity, as in the 4AP (4- aminopyridine) experimental model. Synaptic transmission was also validated by connecting cells into networks and by analyzing emerging network activity (like synaptic spatio-temporal summation processes). Regarding computational resources, simple networks that included up to 4,000 cells were built. Satisfactory computation time was obtained on a standard PC (about a few minutes for 10 seconds of activity).

Published
2007

78. Xenopus transgenic embryos to study early neuronal differentiation

Author

L'Hostis-Guidet, Anne, Madigou, Thierry, Nicolle, O., Guillet, Brigitte, Benquet, Pascal, Tiaho, François, Boujard, Daniel, Interactions cellulaires et moléculaires (ICM), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS), and De Villemeur, Hervé

Subjects
[SDV.BDD] Life Sciences [q-bio]/Development Biology, [SDV.BDD]Life Sciences [q-bio]/Development Biology
Abstract

Poster présenté par A. Guidet-L'hostis

Published
2006

79. Endogenous neuroprotective mechanisms in the hippocampus

Author

Gee, Ce, Benquet, Pascal, Gerber, U., Interactions cellulaires et moléculaires (ICM), Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS), De Villemeur, Hervé, Université de Rennes 1 (UR1), and Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDV.NEU]Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC], [SDV.NEU] Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC]
Published
2006

80. Population activity induced in the hippocampal network

Author

Gee, Ce, Benquet, Pascal, Kampa, Bm, Helmchen, F., Gerber, U., De Villemeur, Hervé, Interactions cellulaires et moléculaires (ICM), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), and Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDV.NEU]Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC], ComputingMethodologies_GENERAL, [SDV.NEU] Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC]
Abstract

Poster

Published
2006

81. Imagerie du potentiel par microscopie multiphonique pour l'étude du système nerveux

Author

Benquet, Pascal, Tiaho, François, Rousseau, Chloé, Bonnec, Georgette, L'Hostis-Guidet, Anne, Boujard, Daniel, Nicolle, O., Renault, A., Rouède, Denis, Interactions cellulaires et moléculaires (ICM), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), and Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDV.BBM.BP]Life Sciences [q-bio]/Biochemistry, Molecular Biology/Biophysics, [SDV.NEU]Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC], ComputingMethodologies_GENERAL
Abstract

Poster

Published
2005

82. Energy deprivation induces network oscillations in the CA3 subfield of organotypic hippocampal slice cultures

Author

Gee, Ce, Benquet, Pascal, Gerber, U., De Villemeur, Hervé, Interactions cellulaires et moléculaires (ICM), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), and Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDV.NEU]Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC], ComputingMethodologies_GENERAL, [SDV.NEU] Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC]
Abstract

Poster

Published
2005

83. Characterization of voltage-sensitive dye for in vivo imaging of neuronal network by two photon microscopy

Author

Benquet, Pascal, Tiaho, François, Percevault, Frédéric, Boujard, Daniel, Renault, A., Rouède, Denis, De Villemeur, Hervé, Interactions cellulaires et moléculaires (ICM), Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS), Université de Rennes 1 (UR1), and Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDV.NEU]Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC], ComputingMethodologies_GENERAL, [SDV.NEU] Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC]
Abstract

Poster

Published
2005

84. Muscarinic receptor stimulation reduces NMDA responses in CA3 hippocampal pyramidal cells via Ca2+-dependent activation of tyrosine phosphatase

Author

Grishin, Aa, Benquet, Pascal, Gerber, U., Interactions cellulaires et moléculaires (ICM), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), University of Zurich, Gerber, U, Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS), and De Villemeur, Hervé

Subjects
3004 Pharmacology, 10242 Brain Research Institute, 2804 Cellular and Molecular Neuroscience, 570 Life sciences, biology, 610 Medicine & health, [SDV.NEU]Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC], [SDV.NEU] Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC], ComputingMethodologies_GENERAL
Abstract

Poster

Published
2004

85. Modulation des récepteurs NMDA par les récepteurs métabotropes au glutamate : une implication dans l'ishemie cérébrale ?

Author

Benquet, Pascal, Gee, Ce, Gerber, U., Interactions Cellulaires et Moléculaires, Université de Rennes (UR)-IFR98-Centre National de la Recherche Scientifique (CNRS), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-IFR98-Centre National de la Recherche Scientifique (CNRS), and De Villemeur, Hervé

Subjects
[SDV.NEU]Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC], [SDV.NEU] Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC], ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2003

86. Neuron to astrocyte communication via cannabinoid receptors is necessary for sustained epileptiform activity in rat hippocampus

Author

Coiret, Guyllaume, Ster, Jeanne, Grewe, Benjamin, Wendling, Fabrice, Helmchen, Fritjof, Gerber, Urs, Benquet, Pascal, Coiret, Guyllaume, Ster, Jeanne, Grewe, Benjamin, Wendling, Fabrice, Helmchen, Fritjof, Gerber, Urs, and Benquet, Pascal

Abstract

Astrocytes are integral functional components of synapses, regulating transmission and plasticity. They have also been implicated in the pathogenesis of epilepsy, although their precise roles have not been comprehensively characterized. Astrocytes integrate activity from neighboring synapses by responding to neuronally released neurotransmitters such as glutamate and ATP. Strong activation of astrocytes mediated by these neurotransmitters can promote seizure-like activity by initiating a positive feedback loop that induces excessive neuronal discharge. Recent work has demonstrated that astrocytes express cannabinoid 1 (CB1) receptors, which are sensitive to endocannabinoids released by nearby pyramidal cells. In this study, we tested whether this mechanism also contributes to epileptiform activity. In a model of 4-aminopyridine induced epileptic-like activity in hippocampal slice cultures, we show that pharmacological blockade of astrocyte CB1 receptors did not modify the initiation, but significantly reduced the maintenance of epileptiform discharge. When communication in astrocytic networks was disrupted by chelating astrocytic calcium, this CB1 receptor-mediated modulation of epileptiform activity was no longer observed. Thus, endocannabinoid signaling from neurons to astrocytes represents an additional significant factor in the maintenance of epileptiform activity in the hippocampus.

Published
2012

97. Muscarinic receptor stimulation reduces NMDA responses in CA3 hippocampal pyramidal cells via Ca2+-dependent activation of tyrosine phosphatase

Author

Grishin, Anton A., Benquet, Pascal, and Gerber, Urs

Subjects
*ACETYLCHOLINE, *G proteins, *CALMODULIN, *PROTEIN-tyrosine phosphatase
Abstract

Abstract: N-methyl-d-aspartate (NMDA)-type glutamate receptors perform critical functions during the development of the nervous system and in the initiation of synaptic plasticity. An important mechanism in setting the gain of NMDA receptors involves the stimulation of G-protein-coupled receptors (GPCRs), which through activation of protein tyrosine kinases leads to an upregulation of NMDA receptors. In contrast, little is known about how NMDA receptors are downregulated. In the present study, we characterized a signaling pathway that mediates the depression of NMDA receptor function in response to stimulation of muscarinic acetylcholine receptors. Whole-cell patch-clamp recordings obtained from CA3 pyramidal cells in organotypic slice cultures revealed that under conditions of low intracellular calcium buffering application of muscarine-depressed NMDA receptor current. The sensitivity of this response to pirenzipine indicated that the M1 acetylcholine receptor is mediating this depression. The muscarine-induced depression of NMDA current was prevented by blocking G-protein function or after depleting intracellular Ca2+ stores with cyclopiazonic acid. Inhibitors of calmodulin prevented the depression whereas blocking calcineurin enhanced the depression of NMDA currents. Blocking tyrosine phosphatase activity with pervanandate converted the muscarine-induced depression into a potentiation of NMDA currents, whereas blocking protein kinase A (H-89), Src kinase (PP2, SU6656), or PKC (GF 109203X) failed to prevent the depression of NMDA currents. As Src tyrosine kinase is known to phosphorylate and upregulate NMDA receptors, we propose that a protein tyrosine phosphatase(s) counteracting the action of Src is the final target in the mAChR-dependent inhibitory signaling cascade. Our data are consistent with a transduction cascade comprising an M1 acetylcholine receptor→G-protein→Ca2+ release→calmodulin→tyrosine phosphatase. [Copyright &y& Elsevier]

Published
2005
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98. In vitro development of P- and R-like calcium currents in insect (Periplaneta americana) embryonic brain neurons

Author

Benquet, Pascal, Pichon, Yves, and Tiaho, François

Subjects
*AMERICAN cockroach, *CALCIUM, *NEURONS, *PERIPLANETA
Abstract

Voltage-gated calcium currents are important for the survival and growth of embryonic cockroach brain neurons in primary culture. In the present experiments, we have studied, using the patch-clamp technique, the evolution with time in culture of the voltage-dependency and of the pharmacological properties of the calcium conductance of these neurons during the formation of a network. We have observed a progressive increase of the high-voltage-activated calcium conductance and a 10 mV shift of the voltage-dependency of activation towards more negative potentials. The proportion of the R-like calcium current component increased during network formation. At the same time, the highly ω-AgaTxIVA-sensitive P-like component of the current is progressively replaced by a component which is less sensitive to the toxin. The origin and functional implications of these modifications are discussed. [Copyright &y& Elsevier]

Published
2004
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100. Transition to seizure in focal epilepsy: From SEEG phenomenology to underlying mechanisms.

Author

Kayabas, Mehmet Alihan, Köksal Ersöz, Elif, Yochum, Maxime, Bartolomei, Fabrice, Benquet, Pascal, and Wendling, Fabrice

Subjects
*PARTIAL epilepsy, *PYRAMIDAL neurons, *NEURAL transmission, *SEIZURES (Medicine), *EPILEPSY
Abstract

Objective Methods Results Significance For the pre‐surgical evaluation of patients with drug‐resistant focal epilepsy, stereo‐electroencephalographic (SEEG) signals are routinely recorded to identify the epileptogenic zone network (EZN). This network consists of remote brain regions involved in seizure initiation. However, the pathophysiological mechanisms underlying typical SEEG patterns that occur during the transition from interictal to ictal activity in distant brain nodes of the EZN remain poorly understood. The primary aim is to identify and explain these mechanisms using a novel physiologically‐plausible model of the EZN.We analyzed SEEG signals recorded from the EZN in 10 patients during the transition from interictal to ictal activity. This transition consisted of a sequence of periods during which SEEG signals from distant neocortical regions showed stereotypical patterns of activity: sustained preictal spiking activity preceding a fast activity occurring at seizure onset, followed by the ictal activity. Spectral content and non‐linear correlation of SEEG signals were analyzed. In addition, we developed a novel neuro‐inspired computational model consisting of bidirectionally coupled neuronal populations.The proposed model captured the essential characteristics of the patient signals, including the quasi‐synchronous onset of rapid discharges in distant interconnected epileptogenic zones. Statistical analysis confirmed the dynamic correlation/de‐decorrelation pattern observed in the patient signals and accurately reproduced in the simulated signals.This study provides insight into the abnormal dynamic changes in glutamatergic and γ‐aminobutyric acid (GABA)ergic synaptic transmission that occur during the transition to seizures. The results strongly support the hypothesis that bidirectional connections between distant neuronal populations of the EZN (from pyramidal cells to vaso‐intestinal peptide‐positive interneurons) play a key role in this transition, while parvalbumin‐positive interneurons intervene in the emergence of rapid discharges at seizure onset. [ABSTRACT FROM AUTHOR]

Published
2024
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