Binocular summation, binocular fusion and the transition to diplopia

Mark Georgeson, Stuart Wallis

Research output: Contribution to journalConference abstractpeer-review


The visual system combines spatial signals from the two eyes to achieve single vision. But if binocular disparity is too large, this perceptual fusion gives way to diplopia. We studied and modelled the processes underlying fusion and the transition to diplopia. The likely basis for fusion is linear summation of inputs onto binocular cortical cells. Previous studies of perceived position, contrast matching and contrast discrimination imply the computation of a dynamicallyweighted sum, where the weights vary with relative contrast. For gratings, perceived contrast was almost constant across all disparities, and this can be modelled by allowing the ocular weights to increase with disparity (Zhou, Georgeson & Hess, 2014). However, when a single Gaussian-blurred edge was shown to each eye perceived blur was invariant with disparity (Georgeson & Wallis, ECVP 2012) – not consistent with linear summation (which predicts that perceived blur increases with disparity). This blur constancy is consistent with a multiplicative form of combination (the contrast-weighted geometric mean) but that is hard to reconcile with the evidence favouring linear combination. We describe a 2-stage spatial filtering model with linear binocular combination and suggest that nonlinear output transduction (eg. ‘half-squaring’) at each stage may account for the blur constancy.
Original languageEnglish
Article number4P1M117
Pages (from-to)319
Number of pages1
Issue numberSuppl.1
Publication statusPublished - 31 Aug 2015
Event38th European Conference on Visual Perception - Liverpool, United Kingdom
Duration: 24 Aug 201627 Aug 2016

Bibliographical note

ECVP 2015 Abstract: 38th European Conference on Visual Perception (ECVP) 2015 Liverpool


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