Contrast summation across eyes and space is revealed along the entire dipper function by a "Swiss cheese" stimulus.

Timothy S. Meese*, Daniel Baker

*Corresponding author for this work

Research output: Contribution to journalArticle

Abstract

Previous contrast discrimination experiments have shown that luminance contrast is summed across ocular (T. S. Meese, M. A. Georgeson, & D. H. Baker, 2006) and spatial (T. S. Meese & R. J. Summers, 2007) dimensions at threshold and above. However, is this process sufficiently general to operate across the conjunction of eyes and space? Here we used a "Swiss cheese" stimulus where the blurred "holes" in sine-wave carriers were of equal area to the blurred target ("cheese") regions. The locations of the target regions in the monocular image pairs were interdigitated across eyes such that their binocular sum was a uniform grating. When pedestal contrasts were above threshold, the monocular neural images contained strong evidence that the high-contrast regions in the two eyes did not overlap. Nevertheless, sensitivity to dual contrast increments (i.e., to contrast increments in different locations in the two eyes) was a factor of ∼1.7 greater than to single increments (i.e., increments in a single eye), comparable with conventional binocular summation. This provides evidence for a contiguous area summation process that operates at all contrasts and is influenced little, if at all, by eye of origin. A three-stage model of contrast gain control fitted the results and possessed the properties of ocularity invariance and area invariance owing to its cascade of normalization stages. The implications for a population code for pattern size are discussed.

Original languageEnglish
Pages (from-to)1-23
Number of pages23
JournalJournal of Vision
Volume11
Issue number1
DOIs
Publication statusPublished - 28 Jan 2011

Bibliographical note

© ARVO. Creative Commons Attribution Non-Commercial No Derivatives License

Keywords

  • contrast discrimination
  • contrast gain control
  • human vision
  • interocular suppression
  • masking
  • rivalry
  • surround suppression

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