Grating and plaid masks indicate linear summation in a contrast gain pool

David J. Holmes, Timothy S. Meese*

*Corresponding author for this work

Research output: Contribution to journalArticle

Abstract

In human vision, the response to luminance contrast at each small region in the image is controlled by a more global process where suppressive signals are pooled over spatial frequency and orientation bands. But what rules govern summation among stimulus components within the suppressive pool? We addressed this question by extending a pedestal plus pattern mask paradigm to use a stimulus with up to three mask components: a vertical 1 c/deg pedestal, plus pattern masks made from either a grating (orientation = -45°) or a plaid (orientation = ±45°), with component spatial frequency of 3 c/deg. The overall contrast of both types of pattern mask was fixed at 20% (i.e., plaid component contrasts were 10%). We found that both of these masks transformed conventional dipper functions (threshold vs. pedestal contrast with no pattern mask) in exactly the same way: The dipper region was raised and shifted to the right, but the dipper handles superimposed. This equivalence of the two pattern masks indicates that contrast summation between the plaid components was perfectly linear prior to the masking stage. Furthermore, the pattern masks did not drive the detecting mechanism above its detection threshold because they did not abolish facilitation by the pedestal (Foley, 1994). Therefore, the pattern masking could not be attributed to within-channel masking, suggesting that linear summation of contrast signals takes place within a suppressive contrast gain pool. We present a quantitative model of the effects and discuss the implications for neurophysiological models of the process. © 2004 ARVO.

Original languageEnglish
Article number7
Pages (from-to)1080-1089
Number of pages10
JournalJournal of Vision
Volume4
Issue number12
DOIs
Publication statusPublished - 22 Dec 2004

Bibliographical note

Creative Commons Attribution Non-Commercial No Derivatives License

Keywords

  • inhibition
  • masking
  • spatial vision
  • summation
  • suppression

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