Epileptic seizures are preceded by a decrease in synchronization

Mormann, Florian; Kreuz, Thomas; Andrzejak, Ralph G.; David, Peter; Lehnertz, Klaus; Elger, Christian E.

doi:10.1016/s0920-1211(03)00002-0

Cited by 421 publications

(239 citation statements)

References 43 publications

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“…Potential relevance of chimera states in this context include bump states [18,19] and the phenomenon of unihemispheric sleep observed in birds and dolphins [20], which sleep with one eye open, meaning that half of the brain is synchronous with the other half being asynchronous. Furthermore, it has been recently hypothesized that chimera states are the route of onset or termination of epileptic seizures [21][22][23][24].…”

Section: Introductionmentioning

confidence: 99%

Chimera patterns in two-dimensional networks of coupled neurons

et al. 2017

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We discuss synchronization patterns in networks of FitzHugh-Nagumo and Leaky Integrate-andFire oscillators coupled in a two-dimensional toroidal geometry. Common feature between the two models is the presence of fast and slow dynamics, a typical characteristic of neurons. Earlier studies have demonstrated that both models when coupled nonlocally in one-dimensional ring networks produce chimera states for a large range of parameter values. In this study, we give evidence of a plethora of two-dimensional chimera patterns of various shapes including spots, rings, stripes, and grids, observed in both models, as well as additional patterns found mainly in the FitzHughNagumo system. Both systems exhibit multistability: For the same parameter values, different initial conditions give rise to different dynamical states. Transitions occur between various patterns when the parameters (coupling range, coupling strength, refractory period, and coupling phase) are varied. Many patterns observe in the two models follow similar rules. For example the diameter of the rings grows linearly with the coupling radius.

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Section: Introductionmentioning

confidence: 99%

Chimera patterns in two-dimensional networks of coupled neurons

et al. 2017

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“…Moreover, the VNS group manifested a further increase in this parameter after 1 year of stimulation. It has been shown that a reduction in synchronization of the gamma band has been detected immediately before an epileptic seizure (Mormann et al, 2003). In addition, experimental data suggest that an antisynchronizing gamma-mediated mechanism may antagonize ictal and interictal epileptogenic spiking activity (Medvedev, 2002) as these figures are proportionally inverse.…”

Section: Discussionmentioning

confidence: 99%

Increase in 20–50Hz (gamma frequencies) power spectrum and synchronization after chronic vagal nerve stimulation

Marrosu¹,

Santoni²,

Puligheddu³

et al. 2005

Clinical Neurophysiology

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Objective: Though vagus nerve stimulation (VNS) is an important option in pharmacoresistant epilepsy, its mechanism of action remains unclear. The observation that VNS desynchronised the EEG activity in animals suggested that this mechanism could be involved in VNS antiepileptic effects in humans. Indeed VNS decreases spiking bursts, whereas its effects on the EEG background remain uncertain. The objective of the present study is to investigate how VNS affects local and inter regional syncronization in different frequencies in pharmacoresistent partial epilepsy. Methods: Digital recordings acquired in 11 epileptic subjects 1 year and 1 week before VNS surgery were compared with that obtained 1 month and 1 year after VNS activation. Power spectrum and synchronization were then analyzed and compared with an epileptic group of 10 patients treated with AEDs only and with 9 non-epileptic patients. Results: VNS decreases the synchronization of theta frequencies (P!0.01), whereas it increases gamma power spectrum and synchronization (!0.001 and 0.01, respectively). Conclusions: The reduction of theta frequencies and the increase in power spectrum and synchronization of gamma bands can be related to VNS anticonvulsant mechanism. In addition, gamma modulation could also play a seizure-independent role in improving attentional performances. Significance: These results suggest that some antiepileptic mechanisms affected by VNS can be modulated by or be the reflection of EEG changes. q

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“…A reduction in synchronization during the early phases of a seizure was shown in patients by intracranial multichannel EEG signal analysis (Mormann et al 2003;Schindler et al 2007a), in cortical and hippocampal slices maintained in vitro (Netoff and Schiff 2002), and by unit activity recordings in models of drug-induced hippocampal seizures in vivo (Cymerblit-Sabba and Schiller 2012). Therefore, diffuse and widespread synchronization is not a typical pattern at the beginning of most partial seizures observed in humans and animals (Jiruska et al 2013).…”

Section: Seizure Onsetmentioning

confidence: 99%

Initiation, Propagation, and Termination of Partial (Focal) Seizures

Curtis

Avoli

2015

Cold Spring Harb Perspect Med

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The neurophysiological patterns that correlate with partial (focal) seizures are well defined in humans by standard electroencephalogram (EEG) and presurgical depth electrode recordings. Seizure patterns with similar features are reproduced in animal models of partial seizures and epilepsy. However, the network determinants that support interictal spikes, as well as the initiation, progression, and termination of seizures, are still elusive. Recent findings show that inhibitory networks are prominently involved at the onset of these seizures, and that extracellular changes in potassium contribute to initiate and sustain seizure progression. The end of a partial seizure correlates with an increase in network synchronization, which possibly involves both excitatory and inhibitory mechanisms.

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Epileptic seizures are preceded by a decrease in synchronization

Cited by 421 publications

References 43 publications

Chimera patterns in two-dimensional networks of coupled neurons

Chimera patterns in two-dimensional networks of coupled neurons

Increase in 20–50Hz (gamma frequencies) power spectrum and synchronization after chronic vagal nerve stimulation

Initiation, Propagation, and Termination of Partial (Focal) Seizures

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