Noise-induced transition in excitable neuron models

We studied the influence of noisy stimulation on the Hodgkin-Huxley neuron model. Rather than examining the noise-related variability of the discharge times of the model - as has been done previously - our study focused on th e effect of noise on the stationary distributions of the membrane potential and gating variables of the model. We observed that a gradual increase in the noise intensity did not result in a gradual change of the distributions . Instead, we could identify a critical intermediate noise range in which t he shapes of the distributions underwent a drastic qualitative change. Name ly, they moved from narrow unimodal Gaussian-like shapes associated with lo w noise intensities to ones that spread widely at large noise intensities. In particular, for the membrane potential and the sodium activation variabl e, the distributions changed from unimodal to bimodal. Thus, our investigat ion revealed a noise-induced transition in the Hodgkin-Huxley model. In ord er to further characterize this phenomenon, we considered a reduced one-dim ensional model of an excitable system, namely the active rotator. For this model, our analysis indicated that the noise-induced transition is associat ed with a deterministic bifurcation of approximate equations governing the dynamics of the mean and variance of the state variable. Finally, we shed l ight on the possible functional importance of this noise-induced transition in neuronal coding by determining its effect on the spike timing precision in models of neuronal ensembles.