Volume 7, Number 10, Article 13, Pages 1-19 doi:10.1167/7.10.13 http://journalofvision.org/7/10/13/ ISSN 1534-7362
Contrast amplification in global texture orientation discrimination
Lawrence G. Appelbaum
Center for Cognitive Neuroscience, Duke University, Durham, NC, USA
[home] [e-mail]
Zhong-Lin Lu
Department of Psychology, University of Southern California, Los Angeles, CA, USA
[home] [e-mail]
George Sperling
Department of Cognitive Science, University of California, Irvine, USA
[home] [e-mail]
Abstract

We show that adding a low-contrast texture stimulus that is far below its own detection threshold to an ambiguously oriented high-contrast texture can produce an easily perceived global orientation. When such a low-contrast (e.g., 0.1%) test texture and a high-contrast (e.g., 2%) amplifier texture are interleaved, the effective strength for global orientation detection closely approximates the product of the two contrasts. Therefore, adding two ambiguous textures, an amplifier texture at 5× its threshold contrast for global orientation discrimination and a test texture at 1/5× its threshold contrast, produces threshold global orientation discrimination, that is, 5× amplification of the below-threshold test texture. The observed 5× amplification factors are larger than facilitation effects reported in other pattern tasks. Amplification is 11× when orientation discrimination thresholds are compared to absolute detection thresholds. For second-order textures, maximum contrast amplification is about 2.5×. A contrast gain control model is presented that accounts for 90% of the variance in observed d′ for texture patterns of differing geometries, exposure durations, and component contrasts. In the model, very low-contrast orientations are represented by power functions of their contrasts, with an exponent greater than two. As the contrast of an amplifier texture increases beyond about 4%, feed-forward gain control exerted by the amplifier ultimately nullifies the amplification effect and produces masking.

View full-text

History
Received November 16, 2006; published July 26, 2007
Citation
Appelbaum, L. G., Lu, Z.-L., & Sperling, G. (2007). Contrast amplification in global texture orientation discrimination. Journal of Vision, 7(10):13, 1-19, http://journalofvision.org/7/10/13/, doi:10.1167/7.10.13.
Keywords
contrast amplification, facilitation, texture, contrast gain control, second order
Downloads
147 Total.
 
Search
for related articles by these authors
for papers that cite this paper
Get citation






jov