Coherence resonance in excitable electronic circuits in the presence of colored noise

Cooperative effect of random and time-periodic coupling strength on synchronization transitions in one-way coupled neural system: mean field approach

The cooperative effect of random coupling strength and time-periodic coupling strengh on synchronization transitions in one-way coupled neural system has been investigated by mean field approach. Results show that cooperative coupling strength (CCS) plays an active role for the enhancement of synchronization transitions. There exist an optimal frequency of CCS which makes the system display the best CCS-induced synchronization transitions, a critical frequency of CCS which can not further affect the CCS-induced synchronization transitions, and a critical amplitude of CCS which can not occur the CCS-induced synchronization transitions. Meanwhile, noise intensity plays a negative role for the CCS-induced synchronization transitions. Furthermore, it is found that the novel CCS amplitude-induced synchronization transitions and CCS frequency-induced synchronization transitions are found.

Effect of colored noise on logical stochastic resonance in bistable dynamics

Recently, Murali [Phys. Rev. Lett. 102, 104101 (2009)] showed that some noisy nonlinear dynamics could be exploited to design nonlinear logic gate based on stochastic resonance (SR). In the paper, inspired by the Murali's articles, we consider the logical stochastic resonance (LSR) phenomenon in a bistable system by cycling various combinations of two logic inputs, in the presence of exponentially correlated noise. The effect of the colored noise on the LSR is evaluated by the success probability of obtained desired logic output. The two major results are presented. First, it shows that the LSR effect can be obtained by changing noise intensity. The logic output is obtained most reliably at an intermediate noise band. There is still a plateau on performance curve of the success probability versus noise intensity. As correlation time increases, the optimal noise band shifts to higher level and peak performance is degraded from 100% accuracy. Due to the influence of the colored noise, the plateau is a bit low and not completely flat. On the other hand, the performance measure can evolve nonmonotonically as correlation time increases, and a SR-like effect is obtained as a result of correlation time. It shows that actually some finite correlation time is better than delta correlation time at certain noise intensities. The study might provide an example where LSR phenomenon can exist robustly in the presence of colored noise.

Roles of external noise correlation in optimal intracellular calcium signaling

The dynamics of a minimal calcium model, which is subjected to white noise or colored noise, was investigated. For white noise, coherence of noise-induced calcium oscillations reached a maximum at an optimal noise intensity, characterizing coherence resonance. Higher resonance peaks could be observed at lower noise intensity when a control parameter is tuned to approach a bifurcation point. For colored noise, a maximal coherence of the oscillations was found for suitable values of both the intensity and the correlation time. Moreover, the coherence of the oscillations exhibited two maxima at two values of noise intensity (correlation time) for appropriate noise correlation time (intensity). In addition, a quantitative description of the effects of noise correlation time on the resonance behavior was presented. The resonance behavior, which is induced either by white noise or colored noise, was interpreted by terms of height and relative width of a spectral peak.

Coherence resonance in a chemical excitable system driven by coloured noise

We investigate how the temporal correlation in excitable systems driven by external noise affects the coherence of the system's response. The coupling to the fluctuating environment is introduced via fluctuations of a bifurcation parameter that controls the local dynamics of the light-sensitive Belousov-Zhabotinsky reaction and of its numerical description, the Oregonator model. Both systems are brought from a highly incoherent regime to a coherent one by an appropriate choice of the correlation time and keeping noise variance constant. This effect has been found both for an Ornstein-Uhlenbeck process and for a dichotomous telegraph signal. In the latter case, we are able to connect the optimal correlation time, for which the system behaviour is most coherent, with a characteristic time scale of the system.

Double coherence resonance in neuron models driven by discrete correlated noise

We study the influence of correlations among discrete stochastic excitatory or inhibitory inputs on the response of the FitzHugh-Nagumo neuron model. For any level of correlation, the emitted signal exhibits at some finite noise intensity a maximal degree of regularity, i.e., a coherence resonance. Furthermore, for either inhibitory or excitatory correlated stimuli, a double coherence resonance is observable. Double coherence resonance refers to a (absolute) maximum coherence in the output occurring for an optimal combination of noise variance and correlation. All of these effects can be explained by taking advantage of the discrete nature of the correlated inputs.

Colored-noise-induced Hopf bifurcations in predator-prey communities

A broad class of (N+1) -species ratio-dependent predator-prey stochastic models, which consist of one predator population and N prey populations, is considered. The effect of a fluctuating environment on the carrying capacities of prey populations is taken into account as colored noise. In the framework of the mean-field theory, approximate self-consistency equations for prey-populations mean density and for predator-population density are derived (to the first order in the noise variance). In some cases, the mean field exhibits Hopf bifurcations as a function of noise correlation time. The corresponding transitions are found to be reentrant, e.g., the periodic orbit appears above a critical value of the noise correlation time, but disappears again at a higher value of the noise correlation time. The nonmonotonous dependence of the critical control parameter on the noise correlation time is found, and the conditions for the occurrence of Hopf bifurcations are presented. Our results provide a possible scenario for environmental-fluctuations-induced transitions between the oscillatory regime and equilibrium state of population sizes observed in nature.