1. Sloan-Swartz Center for Theoretical Neurobiology and
2. Department of Physiology, University of California, San Francisco, 513 Parnassus Avenue, San Francisco, California 94143-0444, USA
3. Center for Theoretical Neuroscience, Center for Neurobiology and Behavior, Columbia University Medical School, N.Y.S.P.I. Kolb Research Annex, 1051 Riverside Drive, Unit 87, New York, New York 10032-2695, USA

Correspondence to: Tatyana O. Sharpee^1,2 Correspondence and requests for materials should be addressed to T.S. (Email: sharpee@phy.ucsf.edu).

Abstract

Sensory neuroscience seeks to understand how the brain encodes natural environments. However, neural coding has largely been studied using simplified stimuli. In order to assess whether the brain's coding strategy depends on the stimulus ensemble, we apply a new information-theoretic method that allows unbiased calculation of neural filters (receptive fields) from responses to natural scenes or other complex signals with strong multipoint correlations. In the cat primary visual cortex we compare responses to natural inputs with those to noise inputs matched for luminance and contrast. We find that neural filters adaptively change with the input ensemble so as to increase the information carried by the neural response about the filtered stimulus. Adaptation affects the spatial frequency composition of the filter, enhancing sensitivity to under-represented frequencies in agreement with optimal encoding arguments. Adaptation occurs over 40 s to many minutes, longer than most previously reported forms of adaptation.

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