Analysis on responses of chaotic Izhikevich neurons to periodic forcing

The Izhikevich neuron model can reproduce various types of neurons, including chaotic neurons, by utilizing appropriate parameter sets. This study analyzes the responses of a periodically forced Izhikevich neuron with chaotic parameters using three measures-the diversity index, the coefficient of variation, and the local variation-to quantify interspike intervals (ISIs). The evaluation of ISIs combining these three measures clarifies the differences in neuronal activities, but evaluation using an individual measure cannot. In addition, we analyzed the change in the stability of the equilibrium points caused by a periodic input on a phase plane. The results indicate that in electrophysiologically feasible parameter sets, the stability of equilibrium points plays a crucial role in determining the critical amplitude around which irregular activities transition to regular ones. Thus, the relationship between neural behavior and the period and amplitude of the input current is contingent upon the existence and stability of equilibrium points.