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Disinhibition-induced transitions between absence and tonic-clonic epileptic seizures
Denggui Fan, Qingyun Wang, Matjaž Perc, 2015, izvirni znanstveni članek

Opis: Electrophysiological experiments have long revealed the existence of two-way transitions between absence and tonic-clonic epileptic seizures in the cerebral cortex. Based on a modified spatially-extended Taylor & Baier neural field model, we here propose a computational framework to mathematically describe the transition dynamics between these epileptic seizures. We first demonstrate the existence of various transition types that are induced by disinhibitory functions between two inhibitory variables in an isolated Taylor & Baier model. Moreover, we show that these disinhibition-induced transitions can lead to stable tonic-clonic oscillations as well as periodic spike with slow-wave discharges, which are the hallmark of absence seizures. We also observe fascinating dynamical states, such as periodic 2-spike with slow-wave discharges, tonic death, bursting oscillations, as well as saturated firing. Most importantly, we identify paths that represent physiologically plausible transitions between absence and tonic-clonic seizures in the modified spatially-extended Taylor & Baier model.
Ključne besede: epilepsy, neuronal dynamics, synchronization, biophysics
Objavljeno v DKUM: 23.06.2017; Ogledov: 754; Prenosov: 334
.pdf Celotno besedilo (2,30 MB)
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Basin stability for chimera states
Sarbendu Rakshit, Bidesh Bera, Matjaž Perc, Dibakar Ghosh, 2017, izvirni znanstveni članek

Opis: Chimera states, namely complex spatiotemporal patterns that consist of coexisting domains of spatially coherent and incoherent dynamics, are investigated in a network of coupled identical oscillators. These intriguing spatiotemporal patterns were first reported in nonlocally coupled phase oscillators, and it was shown that such mixed type behavior occurs only for specific initial conditions in nonlocally and globally coupled networks. The influence of initial conditions on chimera states has remained a fundamental problem since their discovery. In this report, we investigate the robustness of chimera states together with incoherent and coherent states in dependence on the initial conditions. For this, we use the basin stability method which is related to the volume of the basin of attraction, and we consider nonlocally and globally coupled time-delayed Mackey-Glass oscillators as example. Previously, it was shown that the existence of chimera states can be characterized by mean phase velocity and a statistical measure, such as the strength of incoherence, by using well prepared initial conditions. Here we show further how the coexistence of different dynamical states can be identified and quantified by means of the basin stability measure over a wide range of the parameter space.
Ključne besede: synchronization, oscillations, symmetry breaking, network
Objavljeno v DKUM: 23.06.2017; Ogledov: 832; Prenosov: 328
.pdf Celotno besedilo (4,46 MB)
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Synchronous bursts on scale-free neuronal networks with attractive and repulsive coupling
Qingyun Wang, Guanrong Chen, Matjaž Perc, 2011, izvirni znanstveni članek

Opis: This paper investigates the dependence of synchronization transitions of bursting oscillations on the information transmission delay over scale-free neuronal networks with attractive and repulsive coupling. It is shown that for both types of coupling, the delay always plays a subtle role in either promoting or impairing synchronization. In particular, depending on the inherent oscillation period of individual neurons, regions of irregular and regular propagating excitatory fronts appear intermittently as the delay increases. These delay-induced synchronization transitions are manifested as well-expressed minima in the measure for spatiotemporal synchrony. For attractive coupling, the minima appear at every integer multiple of the average oscillation period, while for the repulsive coupling, they appear at every odd multiple of the half of the average oscillation period. The obtained results are robust to the variations of the dynamics of individual neurons, the system size, and the neuronal firing type. Hence, they can be used to characterize attractively or repulsively coupled scale-free neuronal networks with delays.
Ključne besede: synchronization, neuronal networks, noise, stochastic processes, scale-free networks, information transmission delay
Objavljeno v DKUM: 19.06.2017; Ogledov: 824; Prenosov: 354
.pdf Celotno besedilo (933,65 KB)
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Gap junctions and epileptic seizures - two sides of the same coin?
Vladislav Volman, Matjaž Perc, Maxim Bazhenov, 2011, izvirni znanstveni članek

Opis: Electrical synapses (gap junctions) play a pivotal role in the synchronization of neuronal ensembles which also makes them likely agonists of pathological brain activity. Although large body of experimental data and theoretical considerations indicate that coupling neurons by electrical synapses promotes synchronous activity (and thus is potentially epileptogenic), some recent evidence questions the hypothesis of gap junctions being among purely epileptogenic factors. In particular, an expression of inter-neuronal gap junctions is often found to be higher after the experimentally induced seizures than before. Here we used a computational modeling approach to address the role of neuronal gap junctions in shaping the stability of a network to perturbations that are often associated with the onset of epileptic seizures. We show that under some circumstances, the addition of gap junctions can increase the dynamical stability of a network and thus suppress the collective electrical activity associated with seizures. This implies that the experimentally observed post-seizure additions of gap junctions could serve to prevent further escalations, suggesting furthermore that they are a consequence of an adaptive response of the neuronal network to the pathological activity. However, if the seizures are strong and persistent, our model predicts the existence of a critical tipping point after which additional gap junctions no longer suppress but strongly facilitate the escalation of epileptic seizures. Our results thus reveal a complex role of electrical coupling in relation to epileptiform events. Which dynamic scenario (seizure suppression or seizure escalation) is ultimately adopted by the network depends critically on the strength and duration of seizures, in turn emphasizing the importance of temporal and causal aspects when linking gap junctions with epilepsy.
Ključne besede: epilepsy, nonlinear dynamics, electrical synapses, coupling, synchronization
Objavljeno v DKUM: 19.06.2017; Ogledov: 724; Prenosov: 366
.pdf Celotno besedilo (858,25 KB)
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Maruša Babič, 2015, diplomsko delo

Opis: This graduation thesis, entitled Language varieties in the synchronization of the films Madagascar 3 and Open season, consists of two main parts. The theoretical part defines synchronization as a form of audiovisual translation and focuses on the synchronization of animated films. Animated films are made mostly for the youngest viewers, therefore the subject of translating for children is examined. The language varieties of Slovene and English language are described, since there are different dialects represented in the analyzed animated films. The second part focuses on the empirical research, where the language varieties in the synchronization of the animated films Madagascar 3 and Open season are analyzed. The film speech was transcribed for the purpose to conduct the analysis of the language varieties. The prevailing speech variety is colloquial Standard Slovene with the features of colloquial language of Ljubljana. The linguistic features of the main characters were identified and it was investigated how they affect characterization process. Since both films originate from American culture, an analysis of the translation culture-specific and idiomatic expressions was also implemented. The aim of this graduation thesis is to analyze language varieties in the synchronization of the films and investigate whether colloquial language of Ljubljana is used more than other regional colloquial varieties.
Ključne besede: synchronization, animated film, translating for children, language varieties, colloquial language, translating culture-specific terms
Objavljeno v DKUM: 05.06.2015; Ogledov: 1506; Prenosov: 84
.pdf Celotno besedilo (979,78 KB)

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