Intrinsic Coherence Resonance Research Articles

Effect of Spike-Timing-Dependent Plasticity on Intrinsic Coherence Resonance in Newman–Watts Stochastic Hodgkin–Huxley Neuronal Networks

In this paper, we numerically study the effect of spike-timing-dependent plasticity (STDP) on coherence resonance (CR) induced by channel noise in adaptive Newman–Watts stochastic Hodgkin–Huxley neuron networks. It is found that STDP can either enhance or suppress the intrinsic CR when the adjusting rate of STDP decreases or increases. STDP can alter the effects of network randomness and network size on the intrinsic CR. Under STDP, for electrical coupling there are optimal network randomness and network size by which the intrinsic CR becomes strongest, however, for chemical coupling the intrinsic CR is always enhanced as network randomness or network size increases, which are different from the results for fixed coupling. These results show that the intrinsic CR of the neuronal networks can be either enhanced or suppressed by STDP, and there are optimal network randomness and network size by which the intrinsic CR becomes strongest. These findings could provide a new insight into the role of STDP for the information processing and transmission in neural systems.

Effect of Autaptic Activity on Intrinsic Coherence Resonance in Newman–Watts Networks of Stochastic Hodgkin–Huxley Neurons

In this paper, we study the effect of autaptic activity on intrinsic coherence resonance (CR) induced by channel noise in Newman–Watts (NW) networks of stochastic Hodgkin–Huxley (HH) neurons. It is found that autaptic strength and autaptic delay have a big effect on the intrinsic CR. As autaptic strength increases, there is optimal autaptic strength by which the intrinsic CR is most highly enhanced. Autaptic delay can enhance, reduce, or destroy the intrinsic CR, depending on the delay length. Moreover, there are optimal coupling strength and network randomness by which autaptic activity can most highly enhance the intrinsic CR. These results show that autaptic activity has different effects on the intrinsic CR in the neuronal networks, and it can most highly enhance the intrinsic CR at optimal coupling strength and network randomness. These findings could find potential implications of channel noise and autaptic activity for the information processing and transmission in neural systems.

Intrinsic coherence resonance in the chloride-induced temporal dynamics of the iron electrodissolution-passivation in sulfuric acid solutions

The existence of intrinsic coherence resonance (ICR) is demonstrated experimentally for the Fe|0.75M H2SO4 electrochemical system in which the presence of chlorides induces current oscillations. Chlorides, destroying locally the passive oxide film of Fe, lead to pitting corrosion. It is shown that the intensity of the system internal noise, stemming perhaps from fluctuations of ionic concentrations, may be regulated upon changing the applied at the Fe electrode potential (E). Within a certain chloride concentration range (20≤cCl-/mM<50), the ICR occurs within two oscillatory regions. One is located at lower potentials, where the passive-active state dissolution (early stages of pitting) occurs, while the other takes over at higher potentials where the electropolishing state dissolution (late stages of pitting) of the Fe electrode arises. At sufficiently high chloride concentrations (≥50mM) only the electropolishing state dissolution of Fe emerges out of its passive state. To quantify the ICR, the coefficient of variation R and the effective diffusion coefficient Deff were calculated as a function of E for the chloride-induced spiking dynamics of the current, which is the characteristic response of the passive-active state dissolution of Fe. The ICR for the electropolishing state dissolution of Fe was quantified by calculating the coherence factor β as a function of E for the low-amplitude current oscillations established over a limiting current region. The coherence of chloride-induced current oscillations becomes maximal at a certain value of the potential applied at the Fe electrode as a result of an optimal level of the internal noise.

Optimal area and intrinsic coherent resonance of neurons due to ion channel noise under an external stimulus

In this paper, we study the intrinsic coherence resonance of neurons due to ion channel noise under an external stimulus. We find that the external stimulus cannot only increase the spiking coherence of neurons but also increase the optimal area of neuronal membrane for maximal spiking coherence. The optimal membrane area is approximately 3 µm2 without the external stimulus. However, when the external stimulus is 6 µA/cm2, the optimal membrane area is approximately 400 µm2. Because 400 µm2 is the area of a common neuronal soma, our finding has a realistic meaning. Under the external stimulus, common neurons have an optimized conformation to guarantee maximal spiking coherence and the best sub-threshold signal encoding.

Internal noise-driven circadian oscillator in Drosophila

An internal noise-driven oscillator was studied in a two-variable Drosophila model, where both positive feedback and negative feedback are crucial to the circadian oscillations. It is shown that internal noise could sustain reliable oscillations for the parameter which produces a stable steady state in the deterministic system. The noise-sustained oscillations are interpreted by using phase plane analysis. The period of such oscillations fluctuates slightly around the period of deterministic oscillations and the coherence of oscillations becomes the best at an optimal internal noise intensity, indicating the occurrence of intrinsic coherence resonance. In addition, in the oscillatory region, the coherence of noisy circadian oscillations is suppressed by the internal noise, but the period is hardly affected, demonstrating the robustness of the Drosophila model for circadian rhythms to the intrinsic noise.

Noise mediated regularity of porous silicon nanostructures

Interaction of noise with nonlinear electrochemical kinetics involving the etching of porous silicon is studied experimentally. It is realized that by monotonically increasing the level of internal noise, one can tune the regularity of the spatial distribution of pores in silicon nanostructures. This regularity of the noise provoked structures is quantified using a spatial normalized variance technique in conjunction with the calculation of Hurst exponents. Our experimental results indicate the emergence of intrinsic coherence resonance. Consequently, there exists an optimal value of internal noise for which the spatial distribution of nanopores attain maximal regularity. This regularity of the pores can be useful for enhancing the optical response of porous silicon based devices.

Internal Noise-Sustained Circadian Rhythms in a Drosophila Model

Circadian rhythmic processes, mainly regulated by gene expression at the molecular level, have inherent stochasticity. Their robustness or resistance to internal noise has been extensively investigated by most of the previous studies. This work focuses on the constructive roles of internal noise in a reduced Drosophila model, which incorporates negative and positive feedback loops, each with a time delay. It is shown that internal noise sustains reliable oscillations with periods close to 24 h in a region of parameter space, where the deterministic kinetics would evolve to a stable steady state. The amplitudes of noise-sustained oscillations are significantly affected by the variation of internal noise level, and the best performance of the oscillations could be found at an optimal noise intensity, indicating the occurrence of intrinsic coherence resonance. In the oscillatory region of the deterministic model, the coherence of noisy circadian oscillations is suppressed by internal noise, while the period remains nearly constant over a large range of noise intensity, demonstrating robustness of the Drosophila model for circadian rhythms to intrinsic noise. In addition, the effects of time delay in the positive feedback on the oscillations are also investigated. It is found that the time delay could efficiently tune the performance of the noise-sustained oscillations. These results might aid understanding of the exploitation of intracellular noise in biochemical and genetic regulatory systems.

Intrinsic coherence resonance in excitable membrane patches

The influence of intrinsic channel noise on the spiking activity of excitable membrane patches is studied by use of a stochastic generalization of the Hodgkin–Huxley model. Internal noise stemming from the stochastic dynamics of individual ion channels does affect the electric properties of the cell-membrane patches. There exists an optimal size of the membrane patch for which the internal noise alone can cause a nearly regular spontaneous generation of action potentials. We consider the influence of intrinsic channel noise in presence of a constant and an oscillatory current driving for both, the mean interspike interval and the phenomenon of coherence resonance for neuronal spiking. Given small membrane patches, implying that channel noise dominates the excitable dynamics, we find the phenomenon of intrinsic coherence resonance. In this case, the relatively regular spiking behavior becomes essentially independent of an applied stimulus. We observed, however, the occurrence of a skipping of supra-threshold input events due to channel noise for intermediate patch sizes. This effect consequently reduces the overall coherence of the spiking.

Frequency-dependent information coding in neurons with stochastic ion channels for subthreshold periodic forcing

The channel noise that stems from the stochastic nature of the ion channel has important effects on neuronal dynamics. In this context, we investigate the effect of the sub-threshold periodic current forcing on the regularity and synchronization of neuronal spiking activity by using a stochastic extension of the Hodgkin–Huxley model. We demonstrate that the intrinsic coherence resonance is independent of the forcing frequency for very small patch size while it is dependent on the frequency for larger sizes. We also show that the observed phase locking behavior occurs on the positive phase of the periodic current forcing for a small frequency range while the spikes fire most frequently at negative phase as the frequency is increased.

Intrinsic coherence resonance in an electrochemical cell

We study the interaction of intrinsic electrochemical noise with autonomous nonlinear dynamics of a three-electrode electrochemical cell. The amplitude of this intrinsic (internal) noise, regulated by the concentration of chloride ions, is monotonically increased and the provoked dynamics is analyzed. The experimentally constructed coherence factor beta versus the concentration of the chloride ions' curve has a unimodal shape indicating the emergence of intrinsic coherence resonance. The abscissa for the maxima of this unimodal curve corresponds to the optimum value of intrinsic noise where maximum regularity of the invoked dynamics is observed.

Channel noise and synchronization in excitable membranes

Using a stochastic generalization of the Hodgkin–Huxley model, we consider the influence of intrinsic channel noise on the synchronization between the spiking activity of the excitable membrane and an externally applied periodic signal. For small patches, i.e., when the channel noise dominates the excitable dynamics, we find the phenomenon of intrinsic coherence resonance. In this case, the relatively regular spiking behavior is practically independent of the applied external driving; therefore no synchronization occurs. Synchronization takes place, however, only for sufficiently large ion channel assemblies. The neuronal signal processing is thus likely rooted in the collective properties of optimally large assemblies of ion channels.