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Anthony D'Antona, Ari Rosenberg, Steven Shevell; The Neural Locus Underlying Perception of the Craik-O'Brien-Cornsweet Effect. Journal of Vision 2010;10(7):416. doi: 10.1167/10.7.416.
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© ARVO (1962-2015); The Authors (2016-present)
INTRODUCTION: The Craik-O'Brien-Cornsweet (COC) effect occurs when two adjacent equiluminant regions differ in brightness because of a light-dark border between them. This effect, described more than half a century ago, still has an unknown neural basis. This study localizes the origin of the COC effect to a binocular neural locus. METHODS: Experiment 1) Two luminance profiles, with equal baseline luminances, had a central region shaped like an isosceles triangle. One luminance profile had an incremental central region (luminance profile ---^---); the other profile was similar except the isosceles triangle was a decrement. The two luminance profiles were combined; the separation between the two triangles' centers was varied. At certain separations, superposition of the two profiles produced a COC luminance edge. The increment and decrement profiles were either 1) physically summed and presented to one eye (monocular COC border) or 2) presented to separate eyes, so that the COC border existed only after binocular combination (dichoptic COC border). Observers indicated which side of the stimulus appeared brighter. Experiment 2) Monocular and dichoptic COC borders were presented at different contrasts, and observers matched the brightnesses on each side of the COC border. Experiment 3) A monocular COC border was presented to one eye and a grating or moving dots were presented to the other eye so the COC border was suppressed due to binocular rivalry. Observers indicated which side of the stimulus appeared brighter. RESULTS & CONCLUSION: The COC effect occurred for both monocular and dichoptic borders with brightness matches virtually identical in both cases. The COC effect was absent when the border was suppressed by binocular rivalry. Therefore, a monocular COC border is neither necessary nor sufficient for the COC effect. This implies a binocular neural locus after binocular rivalry is resolved.
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