Band-limited noise suppresses contour perception not only of letters but of any objects

N Petkov, M A Westenberg (Institute of Mathematics and Computing Science, University of Groningen, Postbus 800, 9700 AV Groningen, Netherlands; email: petkov@cs.rug.nl; website: http://www.cs.rug.nl/~petkov )

Band-spectrum noise has been shown to suppress the visual perception of printed letters. The suppression exhibits a specific dependence on the spatial frequency of the noise, and the frequency domain of most effective inhibition has been related to the letter size [Solomon and Pelli, 1994 Nature 369 395-397].

In a series of psychophysical experiments we demonstrated that the effect is not specific to the recognition of letters but also applies to other objects and even to single bars. We also showed that the frequency domain of most effective inhibition depends on the letter stroke width rather than on the letter size [Petkov and Westenberg, 2003 Biological Cybernetics 88 236-246]. We attribute the observed effect to non-classical receptive field inhibition in visual area V1 [Nothdurft et al, 1999 Visual Neuroscience 16 15-34]. We introduce a computational model of a complex cell that is based on Gabor-energy filters extended by surround suppression. The results of computer simulations show a dependence of the inhibition effect on the spatial frequency of the noise that is similar to the one measured in the psychophysical experiments and confirm the rightness of the hypothesis for a possible functional role of non-CRF inhibition in the observed suppression effect.