Propagating Dynamics of Interictal Spikes Reconstructed From MEG Recordings

A key question in epilepsy is the organization and size of the neuronal networks necessary for generating seizures. Hypotheses include: a single focal neuronal network drives seizure discharges across the brain, which may or may not be identical with the circuits that generate interictal spikes; or multiple neuronal networks link together in re-entrant loops or other long-range networks. It remains unclear whether any of these hypotheses apply to spontaneous seizures in freely moving animals. We used the tetanus toxin chronic model of epilepsy to test the different predictions made by each hypothesis about the propagation and interaction of epileptic discharges during seizures. Seizures could start in either the injected or noninjected dorsal hippocampus, suggesting that seizures have multifocal onsets in the tetanus toxin model. During seizures, individual bursts propagated in either direction, both between the right and left dorsal hippocampi, and between CA3 and the dentate gyrus in the same hippocampus. These findings argue against one site “driving” seizures or seizures propagating around a limbic loop. Specifically, the side leading each burst switched a median of three times during the first 20 s of a seizure. Analysis of bursts during seizures suggested that the network at each recording site acted like a neuronal oscillator. Coupling of population spikes in right and left CA3 increased during the early part of seizures, but the cross-correlation of their whole-discharge waveforms changed little over the same period. Furthermore, the polarity of the phase difference between population spikes did not follow the phase difference for complete discharges. We concluded that the neuronal aggregate necessary for seizures in our animals comprises multiple spatially distributed neuronal networks and that the increased synchrony of the output (population spike firing) of these networks during the early part of seizures may contribute to seizure generation.

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Dynamics of interictal spikes and high-frequency oscillations during epileptogenesis in temporal lobe epilepsy

Neurobiology of Disease ◽

10.1016/j.nbd.2014.03.012 ◽

2014 ◽

Vol 67 ◽

pp. 97-106 ◽

Cited By ~ 38

Author(s):

Pariya Salami ◽

Maxime Lévesque ◽

Ruba Benini ◽

Charles Behr ◽

Jean Gotman ◽

...

Keyword(s):

Temporal Lobe Epilepsy ◽

Temporal Lobe ◽

High Frequency ◽

Interictal Spikes ◽

High Frequency Oscillations

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Analysis of epileptic neural networks based on the temporal distribution of interictal spikes

2007 3rd International IEEE/EMBS Conference on Neural Engineering ◽

10.1109/cne.2007.369655 ◽

2007 ◽

Author(s):

Kevin J. Staley ◽

F. Edward Dudek

Keyword(s):

Neural Networks ◽

Temporal Distribution ◽

Interictal Spikes

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Theta and gamma hippocampal-neocortical oscillations during the episodic-like memory test: impairment in epileptogenic rats

10.1101/2021.12.09.471759 ◽

2021 ◽

Author(s):

Anton E Malkov ◽

Ludmila Shevkova ◽

Alexandra Latyshkova ◽

Valentina Kitchigina

Keyword(s):

Episodic Memory ◽

Memory Task ◽

Gamma Oscillations ◽

High Amplitude ◽

Memory Test ◽

Interictal Spikes ◽

Paroxysmal Activity ◽

Cortical Oscillations ◽

Gamma Rhythms ◽

Hippocampal Theta

Cortical oscillations in different frequency bands have been shown to be intimately involved in exploration of environment and cognition. Here, the local field potentials in the hippocampus, the medial prefrontal cortex (mPFC), and the medial entorhinal cortex (mEC) were recorded simultaneously in rats during the execution of the episodic-like memory task. The power of hippocampal theta (~4-10 Hz), slow gamma (~25-50 Hz), and fast gamma oscillations (~55-100 Hz) was analyzed in all structures examined. Particular attention was paid to the theta coherence between three mentioned structures. The modulation of the power of gamma rhythms by the phase of theta cycle during the execution of the episodic-like memory test by rats was also closely studied. Healthy rats and rats one month after kainate-induced status epilepticus (SE) were examined. Paroxysmal activity in the hippocampus (high amplitude interictal spikes), excessive excitability of animals, and the death of hippocampal and dentate granular cells in rats with kainate-evoked SE were observed, which indicated the development of seizure focus in the hippocampus (epileptogenesis). One month after SE, the rats exhibited a specific impairment of episodic memory for the what-where-when triad: unlike healthy rats, epileptogenic SE animals did not identify the objects during the test. This impairment was associated with the changes in the characteristics of theta and gamma rhythms and specific violation of theta coherence and theta/gamma coupling in these structures in comparison with the healthy animals. We believe that these disturbances in the cortical areas play a role in episodic memory dysfunction in kainate-treated animals. These findings can shed light on the mechanisms of cognitive deficit during epileptogenesis.

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The Irritative Zone and Seizure Onset Zone in Acute ECOG: The Quest for Relevant Epileptogenic Tissue

Invasive Studies of the Human Epileptic Brain ◽

10.1093/med/9780198714668.003.0010 ◽

2018 ◽

pp. 120-130

Author(s):

André Palmini ◽

Eliseu Paglioli

Keyword(s):

Epilepsy Surgery ◽

Cost Effective ◽

Careful Analysis ◽

Cortical Surface ◽

Interictal Spikes ◽

Intracranial Eeg ◽

Seizure Onset Zone ◽

Cost Effective Approach ◽

Lesion Type ◽

Refractory Seizures

Acute intraoperative electrocorticography (ECoG) is a time-honoured technique to identify the relevant epileptogenic tissue (RET) and hence guide cortical resection to control medically refractory seizures. ECoG identifies the RET through careful analysis of pattern, morphology, frequency, and localization of interictal spikes recorded directly from the exposed cortical surface. Because the development and dissemination of chronic intracranial EEG recording techniques has put emphasis on ictal recordings (thus defining an ictal onset zone), acute ECoG is often considered unnecessary in surgical planning. The chapter describes limitations and advantages of acute ECoG to define the RET in comparison with more costly and risky procedures, particularly subdural grid and SEEG recording. Specifically, it shows how the integration of lesion type and sequentially recorded ECoG spikes during operation may provide a highly cost-effective approach to successful epilepsy surgery.

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