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Vision Res. 1996 Jul;36(13):1907-18.

Fourier and non-Fourier pattern discrimination compared.

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1
Visual Sciences Center, University of Chicago, IL 60637, USA. llin22@midway.uchicago.edu

Abstract

Various studies indicate the existence of non-Fourier visual mechanisms that can extract non-luminance cues (e.g., contrast modulation) as well as a Fourier mechanism that deals with luminance variation only. We compared the pattern discrimination performance of the non-Fourier mechanism with that of the Fourier mechanism by using orientation discrimination and spatial-frequency discrimination tasks. The Fourier patterns used were D6s, the sixth spatial derivative of a Gaussian function multiplied by another Gaussian function in the orthogonal dimension. The corresponding non-Fourier patterns were D6 contrast-modulated cosine gratings. Our results showed a similar trend for the non-Fourier and the Fourier performance at various peak spatial-frequencies or orientations of D6. However, the discrimination threshold of the non-Fourier mechanism was about two-fold higher than that of the Fourier mechanism. The oblique effect was also stronger for non-Fourier patterns. In addition, worse performance for non-Fourier patterns at short stimulus durations (around 33.3 msec) was consistent with the prediction of the two-stage non-Fourier model, which requires more time for the additional rectification and filtering operations.

PMID:
8759430
[Indexed for MEDLINE]
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