Stern-Brocot trees in spiking and bursting of sigmoidal maps

Institute for Multiscale Simulations, Friedrich-Alexander-Universität - 91052 Erlangen, Germany, EU and Departamento de Física, Universidade Federal da Paraíba - 58051-970 João Pessoa, Brazil

Received: 10 October 2012
Accepted: 30 October 2012

Abstract

We study the global organization of oscillations in sigmoidal maps, a class of models which reproduces complex locking behaviors commonly observed in lasers, neurons, and other systems which display spiking, bursting, and chaotic sequences of spiking and bursting. We find periodic oscillations to emerge organized regularly according to the elusive Stern-Brocot tree, a symmetric and more general tree which contains the better-known asymmetric Farey tree as a sub-tree. The Stern-Brocot tree provides a natural and encompassing organization to classify nonlinear oscillations. The mathematical algorithm for generating both trees is exactly the same, differing only in the initial conditions. Such degeneracy suggests that the wrong tree might have been attributed to locking phenomena reported in some of the earlier works.