Soft Mixer Assignment in a Hierarchical Generative Model of Natural Scene Statistics

  • Authors:
  • Odelia Schwartz;Terrence J. Sejnowski;Peter Dayan

  • Affiliations:
  • Howard Hughes Medical Institute, Computational Neurobiology Lab, Salk Institute for Biological Studies, La Jolla, CA 92037, U.S.A. odelia@salk.edu;Howard Hughes Medical Institute, Computational Neurobiology Lab, Salk Institute for Biological Studies, La Jolla, CA 92037, and Department of Biology, University of California at San Diego, La Jol ...;Gatsby Computational Neuroscience Unit, University College, London WC1N 3AR, U.K. dayan@gatsby.ucl.ac.uk

  • Venue:
  • Neural Computation
  • Year:
  • 2006

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Abstract

Gaussian scale mixture models offer a top-down description of signal generation that captures key bottom-up statistical characteristics of filter responses to images. However, the pattern of dependence among the filters for this class of models is prespecified. We propose a novel extension to the gaussian scale mixturemodel that learns the pattern of dependence from observed inputs and thereby induces a hierarchical representation of these inputs. Specifically, we propose that inputs are generated by gaussian variables (modeling local filter structure), multiplied by a mixer variable that is assigned probabilistically to each input from a set of possible mixers. We demonstrate inference of both components of the generative model, for synthesized data and for different classes of natural images, such as a generic ensemble and faces. For natural images, the mixer variable assignments show invariances resembling those of complex cells in visual cortex; the statistics of the gaussian components of the model are in accord with the outputs of divisive normalization models. We also show how our model helps interrelate a wide range of models of image statistics and cortical processing.