Separating the effects of response nonlinearity and internal noise psychophysically.

Full Abstract

A psychophysical method is proposed to separate the contrast dependence of internal response and its noise. The resulting contrast relationships represent a signature of the visual processing stage that limits the human observer's performance. The method was applied to contrast discrimination for sustained and transient Gabor patches with a 3 cycle/deg spatial carrier. For both stimulus types the predominant noise was found to be multiplicative with a power exponent of 0.76-0.85 and the source of this noise preceded by an accelerating signal transducer with a power of 2-2.7. These exponents combine to account for the classic compressive power of about 0.4 for the signal-to-noise ratio in contrast discrimination. The estimated transducer acceleration suggests that there is a direct computation of contrast energy in the visual cortex.

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Author information

Author/s: Kontsevich, Leonid L (LL); Chen, Chien-Chung (CC); Tyler, Christopher W (CW);

Affiliation: Smith-Kettlewell Eye Research Institute, 2318 Fillmore Street, San Francisco, CA 94115, USA. lenny@ski.org

Journal and publication information

Publication Type: Journal Article

Journal: Vision research (Vision Res), published in England. (Language: eng)

Reference: 2002-Jun; vol 42 (issue 14) : pp 1771-84

Dates: Created 2002/07/19; Completed 2002/09/30; Revised 2004/11/17;

PMID: 12127109, status: MEDLINE (last retrieval date: 11/6/2008)

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