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The effect of spatial-frequency filtering on the visual processing of global structure

Lookup NU author(s): Dr Ignacio Serrano-Pedraza

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Abstract

In three experiments we measured reaction times (RTs) and error rates in identifying the global structure of spatially filtered stimuli whose spatial-frequency content was selected by means of three types of 2-D Isotropic filters (Butterworth of order 2, Butterworth of order 10, and a filters with total or partial Gaussian spectral profile). In each experiment, low-pass (LP), band-pass (BP), and high-pass (HP) filtered stimuli, with nine centre or cut-off spatial frequencies, were used. Irrespective of the type of filter, the experimental results showed that: (a) RTs to stimuli with low spatial frequencies were shorter than those to stimuli with medium or high spatial frequencies, (b) RTs to LP filtered stimuli were nearly constant, but they increased in a non-monotonic way with the filter centre spatial frequency in BP filtered stimuli and with the filter cut-off frequency in HP filtered stimuli, and (c) the identification of the global pattern occurred with all visible stimuli used, including BP and HP images without low spatial frequencies. To remove the possible influence of the energy, a fourth experiment was conducted with Gaussian filtered stimuli of equal contrast power (crms = 0.065). Similar results to those described above were found for stimuli with spatial-frequency content higher than 2 cycles deg-1. A model of isotropic first-order visual channels collecting the stimulus spectral energy in all orientations explains the RT data. A subsequent second-order nonlinear amplitude demodulation process, applied to the output of the most energetic first-order channel, could explain the perception of global structure of each spatially filtered stimulus, including images lacking low spatial frequencies. © 2006 a Pion publication.


Publication metadata

Author(s): Sierra-Vazquez V, Serrano-Pedraza I, Luna D

Publication type: Article

Publication status: Published

Journal: Perception

Year: 2006

Volume: 35

Issue: 12

Pages: 1583-1609

Print publication date: 01/01/2006

ISSN (print): 0301-0066

ISSN (electronic): 1468-4233

Publisher: Pion Ltd.

URL: http://dx.doi.org/10.1068/p5364

DOI: 10.1068/p5364

PubMed id: 17283927


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