Cortical cellular phenomena in experimental epilepsy: Ictal manifestations

doi:10.1016/0014-4886(64)90026-3

Experimental Neurology

Volume 9, Issue 4, April 1964, Pages 305-326

https://doi.org/10.1016/0014-4886(64)90026-3 Get rights and content

Abstract

After establishing an epileptogenic “focus” in the cat's cerebral cortex, an intracellular analysis from the involved elements was carried out during the development and course of the organized rhythmical electrographic seizures simultaneously monitored with surface electrodes. Neurons were classified on the basis of their behavior as active or passive. In the former, changes in membrane polarization were observed which characterized the various phases of the ictal episode. The previously present paroxysmal hyperpolarization shifts disappear at the onset and a prominent afterdepolarization develops. During the tonic phase the membrane potential markedly decreases and rhythmical oscillations with (or rerely without) action potentials appear above a sustained excessively depolarized membrane potential level. The clonic phase corresponds to a slow repolarization process and the end of the episode seems to be due to inactivation rather than to true membrane hyperpolarization. Some neurons appear to be activated only in the later phases of the seizure.

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Since the discovery of the human electroencephalogram (EEG), neurophysiology techniques have become indispensable tools in our armamentarium to localize epileptic seizures. New signal analysis techniques and the prospects of artificial intelligence and big data will offer unprecedented opportunities to further advance the field in the near future, ultimately resulting in improved quality of life for many patients with drug-resistant epilepsy. This article summarizes selected presentations from Day 1 of the two-day symposium “Neurophysiology, Neuropsychology, Epilepsy, 2022: Hills We Have Climbed and the Hills Ahead”. Day 1 was dedicated to highlighting and honoring the work of Dr. Jean Gotman, a pioneer in EEG, intracranial EEG, simultaneous EEG/ functional magnetic resonance imaging, and signal analysis of epilepsy. The program focused on two main research directions of Dr. Gotman, and was dedicated to “High-frequency oscillations, a new biomarker of epilepsy” and “Probing the epileptic focus from inside and outside”. All talks were presented by colleagues and former trainees of Dr. Gotman. The extended summaries provide an overview of historical and current work in the neurophysiology of epilepsy with emphasis on novel EEG biomarkers of epilepsy and source imaging and concluded with an outlook on the future of epilepsy research, and what is needed to bring the field to the next level.
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We demonstrated consistently occurring, low-frequency oscillations prior to IED onset.
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N-methyl-d-aspartate glutamate receptors (NMDARs) are involved in numerous central nervous system (CNS) processes, including epileptiform activity. We used a picrotoxin-induced epileptiform activity model to compare the action of different types of NMDAR antagonists in rat brain slices. Paroxysmal depolarizing shifts (PDS) were evoked by external stimulation in the medial prefrontal cortex (mPFC) slices and recorded in pyramidal cells (PC) and in fast-spiking interneurons (FSI). The NMDAR antagonists APV and memantine reduced the duration of PDS. However, the competitive antagonist APV caused similar effects on the PC and FSI, while the open-channel blocker memantine had a much stronger effect on the PDS in the FSI than in the PC. This difference cannot be explained by a corresponding difference in NMDAR sensitivity to memantine because the drug inhibited the excitatory postsynaptic current (EPSC) similarly in both cell types. Importantly, the PDS were significantly longer in the FSI than in the PC. The degree of PDS inhibition by memantine correlated with individual PDS durations in each cell type. Computer modeling of a synaptic network in the mPFC suggests that the different effects of memantine on the PDS in the PC and FSI can be explained by use dependence of its action. An open-channel blocking mechanism and competition with Mg²⁺ ions for the binding site result in pronounced inhibition of the long PDS, whereas the short PDS are weakly sensitive. Our results show that peculiarities of kinetics and the mechanism of action largely determine the effects of NMDAR antagonists on physiological and/or pathological processes.
Spatio-temporal dynamics of interictal activity in musicogenic epilepsy: Two case reports and a systematic review of the literature
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Two patients with ME underwent high-density-electroencephalography (hd-EEG) while listening to ictogenic songs. In one case, musicogenic seizures were elicited. Independent component analysis (ICA) was applied to hd-EEG, and components hosting interictal and ictal elements were identified and localized. Finally, the temporal dynamics of spike-density was studied relative to seizures. All findings were compared against the results of a systematic review on ME, collecting 131 cases.
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Citation Excerpt :
Different types of excitatory amino acid receptors contribute to the spreading of the activity across networks. The propagation process is usually different in the different cortical layers and depends on the pattern of the activating receptors (Matsumoto and Marsan, 1964). It was shown in paired intracellular experiments that epileptiform activities in layer V neurons were always accompanied by similar events in layer II/III cells, and PDSs in layer V always arose before those in layer II.
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¹: Present address of Dr. H. Matsumoto: University of Tokyo School of Medicine, Department of Neuropsychiatry, Motofuji-cho 1, Tokyo, Japan.

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Cortical cellular phenomena in experimental epilepsy: Ictal manifestations

Abstract

Exptl. Neurol.

Exptl. Neurol.

Exptl. Neurol.

Electroencephalog Clin. Neurophysiol.

Electroencephalog. Clin. Neurophysiol.

Electroencephalog. Clin. Neurophysiol.

Electroencephalog. Clin. Neurophysiol.

Electrographic aspects of “epileptic” neuronal aggregates

Epilepsia

Hemmungsphänomene an einzelnen corticalen Neuronen und ihre Bedeutung für die Bremsung convulsiver Entladungen

Arch. Sci. Biol., Bologna

An investigation of primary or direct inhibition

J. Physiol., London

Le tétanos strychnique et le méchanisme de la synchronisation neuronique

Arch. Intern. Physiol.

Potential changes in spinal cord following administration of strychnine

J. Neurophysiol.

Shifts and cortical DC potentials produced by local serial stimuli and their importance for the production of convulsions

Electroencephalog. Clin. Neurophysiol.