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January 1999 Volume 2 Number 1 pp 79 - 87
Predictive coding in the visual cortex: a functional interpretation
of some extra-classical receptive-field effects
Rajesh P. N. Rao1 & Dana H. Ballard2
1. The Salk Institute, Sloan Center for Theoretical Neurobiology
and Computational Neurobiology Laboratory, 10010 N. Torrey Pines
Road, La Jolla, California 92037, USA
2. Department of Computer Science, University of Rochester, Rochester, New York 14627-0226, USA
Correspondence should be addressed to R P N Rao. e-mail: rao@salk.edu
We describe a model of visual processing in which feedback connections
from a higher- to a lower-order visual cortical area carry predictions of
lower-level neural activities, whereas the feedforward connections carry the
residual errors between the predictions and the actual lower-level activities.
When exposed to natural images, a hierarchical network of model neurons implementing
such a model developed simple-cell-like receptive fields. A subset of neurons
responsible for carrying the residual errors showed endstopping and other
extra-classical receptive-field effects. These results suggest that rather
than being exclusively feedforward phenomena, nonclassical surround effects
in the visual cortex may also result from cortico-cortical feedback as a consequence
of the visual system using an efficient hierarchical strategy for encoding
natural images.
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Copyright 1999 Nature America Inc.
