resolving perceptual ambiguity tim andrews university of durham
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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.
Dominance Duration (sec)
0 2 4 6 8 10 12 14 16
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Binocular integration of chromatic signals is dependent on context
no context
context
No Context Context
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ld (
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7n=8
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D Probe size (right - lef t) - arc min
-6 -4 -2 0 2 4 6
R (
righ
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obe
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ft p
robe)
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Can context encourage fusion of physically dissimilar objects?Can context encourage fusion of physically dissimilar objects?
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context
n=8*
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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Right eye
Left eye
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Right eyedominant
Left eyedominant
....
Patch Size: 4 deg Spatial Freq: 1 cycle/deg.Velocity: 1 cycle/sContrast: 30%Gratings: SinusoidalPresentation: 60 sec
% o
f p
att
ern
moti
on
Spatial Frequency (c/deg)
1.0 1.5 2.0
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Standard = 1c/deg
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?
% c
om
ponent
moti
on
S2 S1 S2S1
Rivalrous Non-rivalrous
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% p
att
ern
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oti
on
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?
+rivalry
+adapt
% r
epo
rte
d ri
ght
(45)
% r
epo
rte
d le
ft (
-45)
Adapting orientation (deg)
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0 15 30-15-30-45 45
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(-45)(0)(45)
Adaptation paradigm
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% r
epo
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lue
% r
epo
rte
d re
d %
repo
rted
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sed
Colour
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Red BlueGrey0
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Independent binocular integration for form and colour
adapt
+rivalry
% r
epor
ted
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congruent incongruent fused
Colour
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?
control 1
context
control 2
Panum’s fusional area and rivalry
EEFF
Left
E
Right
F
