- Broida 3302
Jean Carlson (Jean@facilitate.com)
Complex Systems Seminar
Dr. Ann Hermundstad (Department of Physics and Astronomy, University of Pennsylvania)
The statistical regularities of natural scenes are a starting point for understanding the characteristics of early visual processing, such as the center-surround architecture of retinal ganglion cell receptive fields. Can this matching between natural signal statistics and neural processing mechanisms be extended beyond the sensory periphery? Recent work revealed that human sensitivity to fourth-order correlations in synthetic textures, known to arise in cortex, is closely related to the structure of fourth-order spatial correlations in natural scenes. This leads us to propose a specific organizing principle: The perceptual salience of visual textures increases with the variance, or unpredictability, of the corresponding correlations over the ensemble of natural scenes. To test this principle, we examined the statistical regularities of an ensemble of binarized natural images, and we compared the results to psychophysical experiments that measure human sensitivity to synthetic visual textures. Both the ordering and magnitude of natural image variances was found to match perceptual sensitivities to synthetic textures generated with the corresponding correlations. Furthermore, the principal components of the full 9D space of image statistics match the principal components of the corresponding space of sensitivities. These results suggest that central neural mechanisms are efficiently tuned to the higher-order statistics of natural scenes.