title: Activation process in excitable systems with multiple noise sources: Large number of units.
abstract: We study the activation process in large assemblies of type II excitable units whose dynamics is influenced by two independent noise terms. The mean-field approach is applied to explicitly demonstrate that the assembly of excitable units can itself exhibit macroscopic excitable behavior. In order to facilitate the comparison between the excitable dynamics of a single unit and an assembly, we introduce three distinct formulations of the assembly activation event. Each formulation treats different aspects of the relevant phenomena, including the thresholdlike behavior and the role of coherence of individual spikes. Statistical properties of the assembly activation process, such as the mean time-to-first pulse and the associated coefficient of variation, are found to be qualitatively analogous for all three formulations, as well as to resemble the results for a single unit. These analogies are shown to derive from the fact that global variables undergo a stochastic bifurcation from the stochastically stable fixed point to continuous oscillations. Local activation processes are analyzed in the light of the competition between the noise-led and the relaxation-driven dynamics. We also briefly report on a system-size antiresonant effect displayed by the mean time-to-first pulse.
authors.affiliation: Scientific Computing Laboratory, Institute of Physics, University of Belgrade, P. O. Box 68, 11080 Beograd-Zemun, Serbia.
authors.forename: Igor
authors.initials: I
authors.lastname: Franović
authors.affiliation: Faculty of Natural Sciences and Mathematics, University of Maribor, Koroška Cesta 160, SI-2000 Maribor, Slovenia.|Department of Physics, Faculty of Sciences, King Abdulaziz University, Jeddah, Saudi Arabia.
authors.forename: Matjaž
authors.initials: M
authors.lastname: Perc
authors.affiliation: Department of Physics and Mathematics, Faculty of Pharmacy, University of Belgrade, Vojvode Stepe 450, Belgrade, Serbia.
authors.forename: Kristina
authors.initials: K
authors.lastname: Todorović
authors.affiliation: Institute for the Development of Water Resources "Jaroslav Černi," Jaroslava Černog 80, 11226 Belgrade, Serbia.
authors.forename: Srdjan
authors.initials: S
authors.lastname: Kostić
authors.affiliation: Scientific Computing Laboratory, Institute of Physics, University of Beograd, P. O. Box 68, 11080 Beograd-Zemun, Serbia.
authors.forename: Nikola
authors.initials: N
authors.lastname: Burić