Binocular interaction: contrast matching and contrast discrimination are predicted by the same model

Abstract

How do signals from the 2 eyes combine and interact? Our recent work has challenged earlier schemes in which monocular contrast signals are subject to square-law transduction followed by summation across eyes and binocular gain control. Much more successful was a new 'two-stage' modelinwhichtheinitialtransducerwasalmostlinearandcontrastgaincontroloccurredbothpreand post binocular summation. Here we extend that work by: (i) exploring the two-dimensional stimulus space (defined by left-and right-eye contrasts) more thoroughly, and (ii) performing contrast discrimination and contrast matching tasks for the same stimuli. Twenty-five base-stimuli made from 1 c/deg patches of horizontal grating, were defined by the factorial combination of 5 contrasts for the left eye (0.3-32%) with five contrasts for the right eye (0.3-32%). Other than in contrast,thegratingsinthetwoeyeswereidentical.Ina2IFCdiscriminationtask,thebase-stimuli weremasks(pedestals),wherethecontrastincrementwaspresentedtooneeyeonly.Inamatching task,thebase-stimuliwerestandardstowhichobserversmatchedthecontrastofeitheramonocular orbinoculartestgrating.Inthemodel,discriminationdependsonthelocalgradientoftheobserver's internalcontrast-responsefunction,whilematchingequatesthemagnitude(ratherthangradient)of responsetothetestandstandard.Withallmodelparametersfixedbypreviouswork,thetwo-stage model successfully predicted both the discrimination and the matching data and was much more successful than linear or quadratic binocular summation models. These results show that performance measures and perception (contrast discrimination and contrast matching) can be understoodinthesametheoreticalframeworkforbinocularcontrastvision.

Decoding eye-of-origin outside of awareness

“…This suggests that information regarding salience, or perhaps information about relative eye-of-origin (same or different), could persist beyond the stage at which a 'labelled detector' (Watson and Robson, 1981) for explicit ocularity is lost. It is also apparent that observers had some ability to report whether a stimulus was monocular or binocular (64% correct, green bar in Figure 3a), even though these high contrast stimuli would likely appear identical in contrast (Baker et al, 2007). It therefore appears that humans have conscious access to information from their binocular visual system besides a mandatory binocular fusion of the two eyes' inputs.…”

Binocular functional architecture for detection of contrast-modulated gratings

“…It's an interesting prediction, because for luminance gratings it certainly does not hold. At contrasts above about 20%, monocular, binocular and antiphase luminance gratings all appear to have the same contrast (Baker, Meese, & Georgeson, 2007;Baker, Wallis, Georgeson, & Meese, 2012;Huang, Zhou, Zhou, & Lu, 2010). The difference in prediction arises very simply, because monocular channels in our CM model have a contrast-weighted gain of 0.5 (when the carrier is in both eyes; eqn.…”

“…6). The weight for one eye goes up when contrast in the other eye goes down (Baker, Meese, & Georgeson, 2007;Ding & Sperling, 2007;Meese et al, 2006). Uniocular thresholds are lower than monocular because without a carrier in the other eye the weight for the tested eye is higher.…”

A common contrast pooling rule for suppression within and between the eyes

“…Models of suppressive contrast gain control have prompted a resurgence of interest in ocular interactions in psychophysics (Meese & Hess, 2004;Maehara & Goryo, 2005;Ding & Sperling, 2006;Meese et al, 2006;Tsuchiya et al, 2006;Medina et al, 2007;Baker et al, 2007aBaker et al, , 2007bWeiler et al, 2007), electrophysiology (Walker et al 1998;Truchard et al, 2000;Li et al, 2005;Sengpiel & Vorobyov, 2005), and functional imaging (Büchert et al, 2002). These studies have driven the development of binocular models of masking, where interocular suppression forms part of the divisive contrast gain control (Walker et al, 1998;Meese & Hess, 2004;Maehara & Goryo, 2005;Meese et al, 2006;Baker et al, 2007a).…”

“…These studies have driven the development of binocular models of masking, where interocular suppression forms part of the divisive contrast gain control (Walker et al, 1998;Meese & Hess, 2004;Maehara & Goryo, 2005;Meese et al, 2006;Baker et al, 2007a).…”