RESOLVING PERCEPTUAL AMBIGUITY Tim Andrews University of Durham.

RESOLVING PERCEPTUAL AMBIGUITYRESOLVING PERCEPTUAL AMBIGUITY

Tim AndrewsTim Andrews

University of DurhamUniversity of Durham

The visual system uses context to resolve The visual system uses context to resolve ambiguityambiguity

Binocular rivalry

What triggers binocular rivalry (or fusion)?What triggers binocular rivalry (or fusion)?

Alternations in perception can occur between physically Alternations in perception can occur between physically identical stimuli.identical stimuli.

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Binocular integration of chromatic signals is dependent on context

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Can context encourage fusion of physically dissimilar objects?Can context encourage fusion of physically dissimilar objects?

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Andrews and Lotto (2004) Curr. Biol. 14: 48-23

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What rivals during rivalry?

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Pattern motion

Independent binocular integration of form and motion during binocular rivalry

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Pattern motion

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Patch Size: 4 deg Spatial Freq: 1 cycle/deg.Velocity: 1 cycle/sContrast: 30%Gratings: SinusoidalPresentation: 60 sec

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The proportion of binocular pattern motion decreases as the two gratings are made more different in spatial frequency, velocity, colour, contrast and orientation

Andrews and Blakemore (2002) Vision Res. 42: 301-9

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direction ofpattern motion

Patch Size: 0.8 deg Spatial Freq: 1 cycle/deg.Velocity: 1 cycle/sContrast: 30%Gratings: SinusoidalPresentation: 1.5 sec

Can completely suppressed contours contribute to pattern motion during binocular rivalry?

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Form and motion have independent access to perception

Andrews and Blakemore (1999) Nature Neurosci. 2: 405-406

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Can other attributes of vision interact independently during binocular rivalry?

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Independent binocular integration for form and colour

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congruent incongruent fused

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percept or

Holmes, Hancock and Andrews (in preparation)

ConclusionsConclusions

• Fusion and rivalry are dependent on the perceptual meaning of visual stimuli.

• Different attributes of stimulus can interact independently during binocular rivalry.

New project: using TMS to determine where in the visual system binocular rivalry is resolved?

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context

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Panum’s fusional area and rivalry

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