Networks of spiking neurons: the third generation of neural network
  models
Abstract:
The computational power of formal models for networks of spiking neurons is
  compared with that of other neural network models based on McCulloch-Pitts
  neurons (i.e. threshold gates), respectively sigmoidal gates. In particular
  it is shown that networks of spiking neurons are, with regard to the number
  of the neurons that are needed, computationally more powerful than these
  other neural network models. A concrete biologically relevant function is
  exhibited which can be computed by a single spiking neuron (for biologically
  reasonable values of its parameters), but which requires hundreds of hidden
  units on a sigmoidal neuronal net. On the other hand it is known that any
  function that can be computed by a small sigmoidal neural net can also be
  computed by a small network of spiking neurons. This article does not assume
  prior knowledge about spiking neurons, and it contains an extensive list of
  references to the currently available literature on computations in networks
  of spiking neurons and relevant results from neurobiology.
Reference: W. Maass.
 Networks of spiking neurons: the third generation of neural network models.
 In Proc. of the 7th Australian Conference on Neural Networks 1996 in
  Canberra, Australia, pages 1-10, 1996.