A constructive role of internal noise on coherence resonance induced by external noise in a calcium oscillation system

A stochastic cytosolic calcium oscillation model simultaneously driven by external noise and internal noise has been investigated by using the chemical Langevin equation method. When the extracellular stimulation is subthreshold, it is found that the internal-noise coherence resonance can be suppressed by the external noise, while the external-noise coherence resonance can be enhanced by modulating the internal-noise intensity. Besides a qualitative analysis with a competitive mechanism is given for the results, a further explanation is also provided theoretically by using the small noise approximation and bifurcation analysis. (C) 2007 Elsevier Ltd. All rights reserved.