Propriétés fonctionnelles des réseaux et des neurones corticaux chez l'homme et l'animal atteints d'épilepsie-absence : études électrophysiologiques in vivo

Absence epilepsy is an epileptic syndrome which main symptom is a transient alteration of consciousness, with generalized spike-and-wave discharges in EEG, which arise from a dysfunction in the corticothalamic loop and are initiated from a subclass of pyramidal neurons located in the deep layers of the somatosensory cortex. I have investigated two unresolved, issues: 1/ the role of the cortical inhibition in the ictogenic processes, 2/ the neurophysiological mechanisms of sensory processing during absence seizures. By the means of EEG and intracellular recordings in vivo in an animal model: the Genetic Absence Epilepsy Rats from Strasbourg (GAERS), I have examined how the early excitation in theictogenic neurons during seizures was shortly followed by a chlore-dependent synaptic hyperpolarization, concomitant with bursting activities in local GABAergic interneurons. The GABA system has an active inhibitory effect, which constraints the firing of ictogenic neurons within a tight temporal window. In a second study, in human and GAERS, I explored how sensory information was processed during SWDs. In the epileptic child, visual stimulations resulted in occipital evoked potentials, bigger than in non-epileptic subjects. Tactile stimulation of the GAERS applied during seizures induced cortical evoked potentials, reflected in the pyramidal neurons by excitatory synaptic potentials bigger than in interictal condition. Impairment of consciousness during absences do not result from a filtering of sensory information. These researches provide new information on the functional properties of the cortical circuits expressing the electrical paroxysms during absence seizuresL'épilepsie-absence est un syndrome épileptique dont le principal symptôme est une altération transitoire de la conscience, avec décharges pointes-ondes généralisées, qui ont pour origine un dysfonctionnement dans la boucle cortico-thalamique, et naissant dans une sous-population de neurones pyramidaux localisée dans les couches profondes du cortex somatosensoriel. A l'aide d'enregistrements EEG et intracellulaires in vivo dans un modèle animal: les Genetic Absence Epilepsy Rats from Strasbourg, j'ai examiné comment l'excitation initiale des neurones ictogèniques lors des crises est suivie par une hyperpolarisation synaptique chlore-dépendante, concomitante d'une décharge en bouffées dans les interneurones GABAergiques locaux. Le système GABA exerce un effet strictement inhibiteur et contraint la décharge des neurones ictogéniques dans une fenêtre temporelle étroite. Dans une deuxième étude chez l'homme et chez le GAERS, j'ai exploré comment des informations sensorielles sont traitées au cours des DPO. Chez l'enfant épileptique, des stimulations visuelles résultent en des potentiels évoqués occipitaux, plus amples que chez les sujets non-épileptiques. Des stimulations tactiles chez le GAERS induisent lors des crises des potentiels évoqués dans l'EEG et, dans les neurones pyramidaux sous-jacents, des potentiels synaptiques excitateurs plus amples que dans la condition inter-critique. Les troubles de la conscience lors des absences ne résultent donc pas d'un filtrage des informations sensorielles. L'ensemble des recherches fournit des données nouvelles sur les propriétés fonctionnelles des circuits corticaux exprimant les paroxysmes électriques lors des crises d'absenc

Utilisation néonatale des prostaglandines E1 dans la prise en charge des cardiopathies congénitales en réanimation médicale pédiatrique (à propos de 62 cas)

NANCY1-SCD Medecine (545472101) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Propriétés fonctionnelles des réseaux et des neurones corticaux chez l'homme et l'animal atteints d'épilepsie-absence (études électrophysiologiques in vivo)

L épilepsie-absence est un syndrome épileptique dont le principal symptôme est une altération transitoire de la conscience, avec décharges pointes-ondes généralisées, qui ont pour origine un dysfonctionnement dans la boucle cortico-thalamique, et naissant dans une sous-population de neurones pyramidaux localisée dans les couches profondes du cortex somatosensoriel. A l aide d enregistrements EEG et intracellulaires in vivo dans un modèle animal: les Genetic Absence Epilepsy Rats from Strasbourg, j ai examiné comment l excitation initiale des neurones ictogèniques lors des crises est suivie par une hyperpolarisation synaptique chlore-dépendante, concomitante d une décharge en bouffées dans les interneurones GABAergiques locaux. Le système GABA exerce un effet strictement inhibiteur et contraint la décharge des neurones ictogéniques dans une fenêtre temporelle étroite. Dans une deuxième étude chez l homme et chez le GAERS, j ai exploré comment des informations sensorielles sont traitées au cours des DPO. Chez l enfant épileptique, des stimulations visuelles résultent en des potentiels évoqués occipitaux, plus amples que chez les sujets non-épileptiques. Des stimulations tactiles chez le GAERS induisent lors des crises des potentiels évoqués dans l EEG et, dans les neurones pyramidaux sous-jacents, des potentiels synaptiques excitateurs plus amples que dans la condition inter-critique. Les troubles de la conscience lors des absences ne résultent donc pas d un filtrage des informations sensorielles. L ensemble des recherches fournit des données nouvelles sur les propriétés fonctionnelles des circuits corticaux exprimant les paroxysmes électriques lors des crises d absenceAbsence epilepsy is an epileptic syndrome which main symptom is a transient alteration of consciousness, with generalized spike-and-wave discharges in EEG, which arise from a dysfunction in the corticothalamic loop and are initiated from a subclass of pyramidal neurons located in the deep layers of the somatosensory cortex. I have investigated two unresolved, issues: 1/ the role of the cortical inhibition in the ictogenic processes, 2/ the neurophysiological mechanisms of sensory processing during absence seizures. By the means of EEG and intracellular recordings in vivo in an animal model: the Genetic Absence Epilepsy Rats from Strasbourg (GAERS), I have examined how the early excitation in theictogenic neurons during seizures was shortly followed by a chlore-dependent synaptic hyperpolarization, concomitant with bursting activities in local GABAergic interneurons. The GABA system has an active inhibitory effect, which constraints the firing of ictogenic neurons within a tight temporal window. In a second study, in human and GAERS, I explored how sensory information was processed during SWDs. In the epileptic child, visual stimulations resulted in occipital evoked potentials, bigger than in non-epileptic subjects. Tactile stimulation of the GAERS applied during seizures induced cortical evoked potentials, reflected in the pyramidal neurons by excitatory synaptic potentials bigger than in interictal condition. Impairment of consciousness during absences do not result from a filtering of sensory information. These researches provide new information on the functional properties of the cortical circuits expressing the electrical paroxysms during absence seizuresPARIS-BIUSJ-Biologie recherche (751052107) / SudocSudocFranceF

Persistence of cortical sensory processing during absence seizures in human and an animal model: evidence from EEG and intracellular recordings.

Absence seizures are caused by brief periods of abnormal synchronized oscillations in the thalamocortical loops, resulting in widespread spike-and-wave discharges (SWDs) in the electroencephalogram (EEG). SWDs are concomitant with a complete or partial impairment of consciousness, notably expressed by an interruption of ongoing behaviour together with a lack of conscious perception of external stimuli. It is largely considered that the paroxysmal synchronizations during the epileptic episode transiently render the thalamocortical system incapable of transmitting primary sensory information to the cortex. Here, we examined in young patients and in the Genetic Absence Epilepsy Rats from Strasbourg (GAERS), a well-established genetic model of absence epilepsy, how sensory inputs are processed in the related cortical areas during SWDs. In epileptic patients, visual event-related potentials (ERPs) were still present in the occipital EEG when the stimuli were delivered during seizures, with a significant increase in amplitude compared to interictal periods and a decrease in latency compared to that measured from non-epileptic subjects. Using simultaneous in vivo EEG and intracellular recordings from the primary somatosensory cortex of GAERS and non-epileptic rats, we found that ERPs and firing responses of related pyramidal neurons to whisker deflection were not significantly modified during SWDs. However, the intracellular subthreshold synaptic responses in somatosensory cortical neurons during seizures had larger amplitude compared to quiescent situations. These convergent findings from human patients and a rodent genetic model show the persistence of cortical responses to sensory stimulations during SWDs, indicating that the brain can still process external stimuli during absence seizures. They also demonstrate that the disruption of conscious perception during absences is not due to an obliteration of information transfer in the thalamocortical system. The possible mechanisms rendering the cortical operation ineffective for conscious perception are discussed, but their definite elucidation will require further investigations

Electrophysiological technical procedures

International audienceThe reliability of the interpretation of SEEG data depends entirely on the technical quality of the acquisition recording. Digitalization of data and the development of computer technology, over the last 20 years have transformed electrophysiological procedures. Recording equipment must be able to record concomitantly clinical events and brain electrical activity. Recording is carried out during wakefulness and sleep and with use of various activation methods (hyperventilation, intermittent photic stimulation). Intracerebral electrical stimulations (with low and high frequency) and the acquisition of evoked potentials complete the SEEG exploration. This chapter will discuss the characteristics of video-EEG recording equipment, procedures for acquisition and creation of SEEG montages, technical recording and activations, procedures of intracerebral electrical stimulations and the acquisition of evoked potentials

Properties of sensory-evoked intracellular responses from non-epileptic rats and GAERS.

<p>Pooled data of the mean latency of sensory-evoked responses (A, Resp. latency), mean amplitude of subthreshold dPSPs (B, Resp. amplitude), action potential firing probability (C, AP probability) and corresponding latency (D, AP latency) from non-epileptic Wistar rats (Wistar) and GAERS, during interictal and seizure (SWD) periods. Only the amplitude of subthreshold dPSPs during SWDs was found significantly different compared to that measured during interictal activity. *p<0.05; ns, nonsignificant. Bar graphs represent the mean ± SEM (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0058180#s3" target="_blank">results</a> for detailed quantifications).</p

Sensory responses intracellularly recorded in S1 cortex neurons from non-epileptic Wistar rats and GAERS.

<p>Each panel depicts the sensory stimulus (top traces) and the corresponding responses in the EEG (middle records) and in a pyramidal neuron (bottom records) simultaneously recorded. (A1, B1) Typical examples of single sensory-evoked responses recorded from a control Wistar rat (A1) and in a GAERS (B1), during an interictal epoch (left) and during a seizure (right). The dashed boxes enclose the responses induced by whiskers deflection. (A2, B2) Superimposition (n = 4) of wERPs and corresponding suprathreshold intracellular responses (Supra-resp) in control (A2) and epileptic (B2) animals, during interictal (B2, left) and seizure (B2, right) periods. (A3, B3) Same representation as in A2 and B2 for neuronal responses that remained subthreshold in the three conditions. In A2, A3, B2, B3, the mean value of membrane potential at the onset of the cellular responses is indicated by the arrowheads. In A3 and B3, action potentials are truncated for clarity. Results depicted in A and B are from single neurons.</p

Spontaneous intracellular activities of S1 cortex neurons from non-epileptic rats and GAERS.

<p>(A1–B1) Superimposed slice drawings, made from the stereotaxic rat brain atlas from Paxinos and Watson (1986) at the indicated distances (in millimetres) from the bregma. Black and red dots indicate the location of intracellularly recorded neurons from the S1 cortex of control Wistar rats (A1) and GAERS (B1), respectively. Mo, motor cortex; CPu, caudate-putamen. (A2, B2, B3) Simultaneous recordings of spontaneous intracellular activities (bottom records) and corresponding EEG waves (top records) from a non-epileptic rat (A2) and from a GAERS, during interictal (B2) and ictal (B3) periods. Note that the interictal irregular membrane potential fluctuations and firing pattern was replaced, at the occurrence of a SWD, by rhythmic suprathreshold membrane depolarizations superimposed on a tonic hyperpolarization that lasted for the entire epileptic episode. The arrowheads indicate membrane potential values. Records shown in B2 and B3 are from the same neuron. (C) Pooled values of mean membrane potential (Vm) from pyramidal neurons recorded in normal rats (Wistar, n = 14 neurons) and in GAERS (n = 19 neurons) during SWDs, at the sustained hyperpolarization associated with seizures (Envelope) and during interictal periods (Interictal). ***p<0.001; ns, nonsignificant.</p

wERPs are not significantly altered during SWDs in the GAERS.

<p>(A1–C1) Frequency power spectra computed from 5 s of spontaneous EEG activity, including the truncated records shown in the corresponding <i>insets</i>, from a non-epileptic rat (A1) and during interictal (B1) and ictal (C1) periods in a GAERS. (A2–C2) Average (the number of trials is indicated) wERPs obtained in the three conditions as shown in A1–C1, in response to air-puff stimuli applied to the contralateral whiskers (top traces). The latency of wERPs was measured as the time difference between the onset of the air-puff (solid line) and the peak of the first negativity of evoked potentials (dashed line). (D) Superimposition of the average records shown in A2–C2, with normalized amplitude (using the initial negative component as the amplitude reference) and using the onset of the sensory stimulus as the time reference. Note the constancy in latency and shape of the first component of the wERPs in the non-epileptic Wistar rat and the GAERS. (E) Pooled data showing that the peak latency of the early sensory responses was not significantly different in the three conditions (Control Wistar rats, n = 11; Interictal periods (Inter) and SWDs in GAERS, n = 11; p = 0.4) (left), with an amplitude during SWDs that remained unchanged compared to the corresponding interictal periods (n = 11 GAERS; p = 0.7) (right). Bar graphs represent the mean ± SEM (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0058180#s3" target="_blank">results</a> for detailed quantifications).</p