Rate-coded Restricted Boltzmann Machines for Face
  Recognition
  Yee Whye Teh
  Department of Computer Science
  University of Toronto
  Toronto M5S 2Z9, Canada
  
  Geoffrey Hinton
  Gatsby Computational Neuroscience Unit
  University College London
  17 Queen Square, London WC1N 3AR, UK
  Abstract
  We describe a neurally-inspired, unsupervised learning algorithm
  that builds a non-linear generative model for pairs of face images from the same
  individual. Individuals are then recognized by finding the highest relative probability
  pair among all pairs that consist of a test image and an image whose identity is known.
    Our method compares favorably with other methods in the literature.  The
  generative model consists of a single layer of rate-coded, non-linear feature detectors
  and it has the property that, given a data vector, the true posterior probability
  distribution over the feature detector activities can be inferred rapidly without
  iteration or approximation.  The weights of the feature detectors are learned by
  comparing the correlations of pixel intensities and feature activations in tow phases:
    When the network is observing real data and when it is observing reconstructions of
  real data generated from the feature activations.