August 2010
Volume 10, Issue 7
Free
Meeting Abstract  |   August 2010
Detecting contrast differences in binocular and dichoptic vision: we use monocular or binocular channels, whichever gives the MAX response
Author Affiliations
  • Mark Georgeson
    School of Life & Health Sciences, Aston University, Birmingham, UK
  • Tim Meese
    School of Life & Health Sciences, Aston University, Birmingham, UK
  • Daniel Baker
    School of Life & Health Sciences, Aston University, Birmingham, UK
Journal of Vision August 2010, Vol.10, 350. doi:10.1167/10.7.350
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      Mark Georgeson, Tim Meese, Daniel Baker; Detecting contrast differences in binocular and dichoptic vision: we use monocular or binocular channels, whichever gives the MAX response. Journal of Vision 2010;10(7):350. doi: 10.1167/10.7.350.

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Two eyes are often better than one. Models based on binocular summation of signals from each eye, with interocular contrast gain control and a single binocular output channel, account well for detection, discrimination and perception of monocular and binocular contrast. We now ask whether monocular signals also remain available to perception. Horizontal 1c/deg sine-wave gratings of contrast C were presented to both eyes for 200ms in 2AFC discrimination tasks, to determine whether contrast increments (C+dC) in one eye were more difficult to detect when accompanied by contrast decrements (C-dC) in the other eye. Summation or averaging over the two eyes should make these opposite changes cancel. Results consistently showed no cancellation. Binocular increments or decrements were more detectable than monocular ones, but thresholds for the hybrid increment/decrement condition were close to those for monocular contrast increment (on the binocular pedestal). Since the binocular channel must suffer cancellation, its absence here implies that monocular signals can remain available to perception and decision, alongside the combined binocular response. Despite this, monocular decrements of contrast on a binocular pedestal were unusually difficult to detect. An extended version of our 2-stage gain-control model (Meese, Georgeson & Baker, Journal of Vision 2006), now incorporating left-eye, right-eye and binocular channels, accurately explained the patterns of threshold variation over at least 7 distinct forms of dipper function. Importantly, the model observer is assumed to pick only the MAX response across the 3 types of channel. This normally arises from the binocular channel, which can thus occlude useful information in the monocular channels. But when the pedestal gratings are out-of-phase in the 2 eyes, interocular suppression wipes out the binocular response, and monocular channels mediate the task. This switch from binocular to monocular responses may be the early, local basis for binocular rivalry.

Georgeson, M. Meese, T. Baker, D. (2010). Detecting contrast differences in binocular and dichoptic vision: we use monocular or binocular channels, whichever gives the MAX response [Abstract]. Journal of Vision, 10(7):350, 350a, http://www.journalofvision.org/content/10/7/350, doi:10.1167/10.7.350. [CrossRef]
 
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