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

Meese, Timothy S. and Baker, Daniel (2011). Contrast summation across eyes and space is revealed along the entire dipper function by a "Swiss cheese" stimulus. Journal of vision, 11 (1), pp. 1-23.

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Official URL: http://www.journalofvision.org/content/11/1/23

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.

Item Type:Article
Additional Information:Open Access
Uncontrolled Keywords:human vision, contrast discrimination, masking, contrast gain control, interocular suppression, rivalry, surround suppression
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ID Code:12735
Deposited By:Daniel Baker
Deposited On:09 Feb 2011 12:25
Last Modified:20 Feb 2014 07:49

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