Characteristics of critical amplitude of a sinusoidal stimulus in a model neuron

摘要

The characteristics of the critical amplitude of a sinusoidal stimulus in a model neuron, Morris-Lecar model, areinvestigated numerically. It is important in the study of stochastic resonance to determine whether a periodic stimulusis subthreshold or not. The critical amplitude as a function of the stimulus frequency is not a constant, but a curve,which is the boundary between subthreshold and suprathreshold stimulation. It has been considered that this curve isU-shaped in the previous investigations, and this has been accepted as a universal phenomenon. Nevertheless, we thinkthat it is only true for a type of neuron: namely, resonators. Actually, there exists another type of neuron, integrators,which can undergo a saddle-node on invariant circle bifurcation from the rest state to the firing state. For the latterwe find that the critical amplitude increases monotonically as the frequency of sinusoidal stimulus is increased. This isshown by way of the Morris-Lecar model. As a consequence, the critical amplitude curve is studied further, and thedynamical mechanisms underlying the change in critical amplitude curve are uncovered. The results of this paper canprovide a reference to choose the subthreshold periodic stimulus.