1. Aging transitions of multimodal oscillators in multilayer networksUroš Barać, Matjaž Perc, Marko Gosak, 2024, original scientific article Abstract: When individual oscillators age and become inactive, the collective dynamics of coupled oscillators is often affected as well. Depending on the fraction of inactive oscillators or cascading failures that percolate from crucial information exchange points, the critical shift toward macroscopic inactivity in coupled oscillator networks is known as the aging transition. Here, we study this phenomenon in two overlayed square lattices that together constitute a multilayer network, whereby one layer is populated with slow Poincaré oscillators and the other with fast Rulkov neurons. Moreover, in this multimodal setup, the excitability of fast oscillators is influenced by the phase of slow oscillators that are gradually inactivated toward the aging transition in the fast layer. Through extensive numerical simulations, we find that the progressive inactivation of oscillators in the slow layer nontrivially affects the collective oscillatory activity and the aging transitions in the fast layer. Most counterintuitively, we show that it is possible for the intensity of oscillatory activity in the fast layer to progressively increase to up to 100%, even when up to 60% of units in the slow oscillatory layer are inactivated. We explain our results with a numerical analysis of collective behavior in individual layers, and we discuss their implications for biological systems.
Keywords: collective dynamics, coupled oscillators, dynamics of networks, network resilience, robustness, synchronization transition
Published in DKUM: 28.02.2025; Views: 0; Downloads: 429
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2. Both electrical and metabolic coupling shape the collective multimodal activity and functional connectivity patterns in beta cell collectives : a computational model perspectiveMarko Šterk, Uroš Barać, Andraž Stožer, Marko Gosak, 2023, original scientific article Abstract: Pancreatic beta cells are coupled excitable oscillators that synchronize their activity via different communication pathways. Their oscillatory activity manifests itself on multiple timescales and consists of bursting electrical activity, subsequent oscillations in the intracellular Ca 2 + , as well as oscillations in metabolism and exocytosis. The coordination of the intricate activity on the multicellular level plays a key role in the regulation of physiological pulsatile insulin secretion and is incompletely understood. In this paper, we investigate theoretically the principles that give rise to the synchronized activity of beta cell populations by building up a phenomenological multicellular model that incorporates the basic features of beta cell dynamics. Specifically, the model is composed of coupled slow and fast oscillatory units that reflect metabolic processes and electrical activity, respectively. Using a realistic description of the intercellular interactions, we study how the combination of electrical and metabolic coupling generates collective rhythmicity and shapes functional beta cell networks. It turns out that while electrical coupling solely can synchronize the responses, the addition of metabolic interactions further enhances coordination, the spatial range of interactions increases the number of connections in the functional beta cell networks, and ensures a better consistency with experimental findings. Moreover, our computational results provide additional insights into the relationship between beta cell heterogeneity, their activity profiles, and functional connectivity, supplementing thereby recent experimental results on endocrine networks.
Keywords: pancreatic, beta cells, oscilators, calcium signaling, cells signaling
Published in DKUM: 10.12.2024; Views: 0; Downloads: 7
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3. Determinants of collective failure in excitable networksUroš Barać, Matjaž Perc, Marko Gosak, 2023, original scientific article Abstract: We study collective failures in biologically realistic networks that consist of coupled excitable units. The networks have broad-scale degree distribution, high modularity, and small-world properties, while the excitable dynamics is determined by the paradigmatic FitzHugh–Nagumo model. We consider different coupling strengths, bifurcation distances, and various aging scenarios as potential culprits of collective failure. We find that for intermediate coupling strengths, the network remains globally active the longest if the high-degree nodes are first targets for inactivation. This agrees well with previously published results, which showed that oscillatory networks can be highly fragile to the targeted inactivation of low-degree nodes, especially under weak coupling. However, we also show that the most efficient strategy to enact collective failure does not only non-monotonically depend on the coupling strength, but it also depends on the distance from the bifurcation point to the oscillatory behavior of individual excitable units. Altogether, we provide a comprehensive account of determinants of collective failure in excitable networks, and we hope this will prove useful for better understanding breakdowns in systems that are subject to such dynamics.
Keywords: collective behavior, excitable media, complex network, neuronal dynamics
Published in DKUM: 10.06.2024; Views: 163; Downloads: 24
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4. Dinamična robustnost in prehod v staranje v omrežjih sklopljenih oscilatorjev : magistrsko deloUroš Barać, 2023, master's thesis Abstract: Biološka omrežja so v splošnem odporna na okvare posameznih enot, toda v vsakem omrežju obstaja prelomna točka, pri kateri se sposobnost delovanja poslabša do neuporabnosti. To se lahko kaže kot bolezen ali izguba funkcije, kar je pogosto težko odpraviti. Iz tega razloga je pomembno preučevati pojave takih kolektivnih okvar, ki sledijo postopni disfunkciji posameznih gradnikov, da bi lahko sprejeli ukrepe za njihovo preprečitev. Na področju dinamičnih sistemov se tovrstni prehodi imenujejo prehod v staranje (ang. aging transition). Temu pojavu se posvetimo tudi v tej magistrski nalogi in najprej prikažemo koncept prehoda v staranje v omrežjih globalno sklopljenih in homogenih oscilatorjev z limitnim ciklom, pri katerih dinamiko posameznih oscilatorjev določa Poincaréjev oscilator. Pokažemo, da se prehodi v staranje v takih omrežjih obnašajo dokaj predvidljivo ter da imata jakost sklopitve in oddaljenost od točke bifurkacije monotono vlogo pri dinamični robustnosti sistema. Nato se osredotočimo na preučevanje kolektivnih okvar v biološko bolj realističnih omrežjih, ki sestojijo iz povezanih ekscitabilnih enot, interakcije med njimi pa izkazujejo lastnosti kompleksnega omrežja. Le-to je heterogeno in ima visoko modularnost in lastnosti mrež malega sveta. Dinamiko posameznih ekscitabilnih elementov določa paradigmatski model FitzHugh-Nagumo, ki se pogosto uporablja za simulacije dinamike električno ekscitabilnih celic. Kot dejavnike za kolektivno odpoved obravnavamo jakost sklopitve, razdaljo od točke bifurkacije in poleg tega še različne strategije staranja. Ugotovimo, da pri srednjih jakostih sklopitve omrežje ostane globalno aktivno najdlje, kadar se v omrežju najprej deaktivirajo vozli z velikim številom povezav. To se dobro ujema s predhodno objavljenimi rezultati. Ti so pokazali, da so lahko, predvsem pri šibki sklopitvi, omrežja oscilatorjev zelo občutljiva na ciljno deaktivacijo vozlov z majhnim številom povezav. Toda naše podrobne analize pokažejo, da najučinkovitejša strategija za doseganje kolektivne odpovedi ni le nemonotono odvisna od jakosti sklopitve, temveč je odvisna od sovisnega vpliva jakosti sklopitve in oddaljenosti točke bifurkacije, ki kroji raven stabilnosti oscilatornega režima. V magistrski nalogi tako podamo celovit opis dejavnikov kolektivne odpovedi v ekscitabilnih omrežjih, kar vodi do globljega razumevanja okvar v takih sistemih.
Keywords: prehod v staranje, oscilatorji z limitnim ciklom, ekscitabilni oscilatorji, kompleksno omrežje, bifurkacija, globalna aktivnost.
Published in DKUM: 28.09.2023; Views: 540; Downloads: 55
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