Email updates

Keep up to date with the latest news and content from BMC Neuroscience and BioMed Central.

This article is part of the supplement: Seventeenth Annual Computational Neuroscience Meeting: CNS*2008

Open Access Poster presentation

A hierarchical predictive coding model of visual processing

Boris Vladimirskiy*, Walter Senn* and Robert Urbanczik

Author Affiliations

Department of Physiology, University of Bern, 3012 Bern, Switzerland

For all author emails, please log on.

BMC Neuroscience 2008, 9(Suppl 1):P111  doi:10.1186/1471-2202-9-S1-P111

The electronic version of this article is the complete one and can be found online at: http://www.biomedcentral.com/1471-2202/9/S1/P111


Published:11 July 2008

© 2008 Vladimirskiy et al; licensee BioMed Central Ltd.

Poster presentation

The roles for top-down signals in visual processing have been intensively studied experimentally in the last few years and have also been modeled theoretically. In particular, predictive coding, where feedback from higher cortical areas carries expectations of lower level activity, has been shown to explain the emergence of extra-classical receptive field effects [1].

Since top-down predictions cannot be independent of the bottom-up input, the interpretation of a visual scene must be an iterative process in which the initial activation pattern relaxes to a solution matching expectation with sensory experience. However, in models, such as the one of Rao and Ballard, where top-down effects propagate over all layers of the visual hierarchy, the relaxation times are too slow compared to the time scale of visual processing. Our starting point is the mathematical observation that in predictive coding relaxation results in each higher layer essentially performing principal component analysis of the activity in the preceding lower layer. We show how this analysis can be done without propagating top-down effects through the entire visual hierarchy. In our model, not only the top-down connectivity, but also the effective resulting feedback is confined to proximal layers, yielding fast relaxation. This suggests a way for the visual system to square the need for fast processing with the integration of top-down clues.

We also make it explicit that in a biologically plausible implementation each layer requires both coding for stimulus representation and for the prediction error. This sheds new light on the interpretation of activation patterns observed in V4 which have seemed impossible to reconcile with predictive coding [2].

References

  1. Rao RP, Ballard DH: Predictive coding in the visual cortex: a functional interpretation of some extra-classical receptive-field effects.

    Nat Neurosci 1999, 2(1):9-10. PubMed Abstract | Publisher Full Text OpenURL

  2. Rainer G, Lee H, Logothetis NK: The effect of learning on the function of monkey extrastriate visual cortex.

    PLoS Biol 2004, 2(2):E44. PubMed Abstract | Publisher Full Text | PubMed Central Full Text OpenURL