Hopf Bifurcation and Chaos in a Single Inertial Neuron Model with Time   Delay
  A delayed differential equation modelling a single neuron with inertial term is considered in this paper. Hopf bifurcation is studied by using the normal form theory of retarded functional differential equations. When adopting a nonmonotonic activation function, chaotic behavior is observed. Phase plots, waveform plots, and power spectra are presented to confirm the chaoticity. 
Chunguang Li, Guanrong Chen, Xiaofeng Liao, Juebang Yu