Biological experimental observations of an unnoticed chaos as simulated by the Hindmarsh-Rose model

PLoS One. 2013 Dec 10;8(12):e81759. doi: 10.1371/journal.pone.0081759. eCollection 2013.


An unnoticed chaotic firing pattern, lying between period-1 and period-2 firing patterns, has received little attention over the past 20 years since it was first simulated in the Hindmarsh-Rose (HR) model. In the present study, the rat sciatic nerve model of chronic constriction injury (CCI) was used as an experimental neural pacemaker to investigate the transition regularities of spontaneous firing patterns. Chaotic firing lying between period-1 and period-2 firings was observed located in four bifurcation scenarios in different, isolated neural pacemakers. These bifurcation scenarios were induced by decreasing extracellular calcium concentrations. The behaviors after period-2 firing pattern in the four scenarios were period-doubling bifurcation not to chaos, period-doubling bifurcation to chaos, period-adding sequences with chaotic firings, and period-adding sequences with stochastic firings. The deterministic structure of the chaotic firing pattern was identified by the first return map of interspike intervals and a short-term prediction using nonlinear prediction. The experimental observations closely match those simulated in a two-dimensional parameter space using the HR model, providing strong evidences of the existence of chaotic firing lying between period-1 and period-2 firing patterns in the actual nervous system. The results also present relationships in the parameter space between this chaotic firing and other firing patterns, such as the chaotic firings that appear after period-2 firing pattern located within the well-known comb-shaped region, periodic firing patterns and stochastic firing patterns, as predicted by the HR model. We hope that this study can focus attention on and help to further the understanding of the unnoticed chaotic neural firing pattern.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Biological Clocks*
  • Computer Simulation*
  • Models, Neurological*
  • Rats
  • Sciatic Nerve / injuries*
  • Sciatic Nerve / physiopathology*
  • Synaptic Transmission*

Grant support

This work was supported by the National Natural Science Foundation of China under Grant Nos. 11072135 and 10772101, and the Fundamental Research Funds for Central Universities of Tongji University under Grant No 1330219127. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.