Cortical Dynamics Underlying Waves of Perceptual Dominance

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Cortical Dynamics Underlying Waves of Perceptual
Dominance
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People Involved in this Project
Randolph Blake Vanderbilt University
David Heeger New York University
Sang-Hun Lee Seoul National University
Hugh Wilson York University
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Binocular Rivalry -- a psychophysical tool for
studying cortical dynamics
left eye
right eye
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Characteristics of Binocular Rivalry
Dominance tends to be unitary when rival
targets are small but piecemeal when targets are
large Successive phases of dominance are
unpredictable in duration Visual adaptation
plays a role in causing state changes
Reciprocal inhibition between feature
detectors Self-adaptation, plus noise
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Spatio-temporal dynamics during state transitions
right eye
left eye
dominance states over time
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Spatio-temporal dynamics during state transitions
wave-like transitions between dominance
right eye
left eye
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Spatio-temporal dynamics during state
transitions Traveling waves in rivalry
View this anaglyph through red/green glasses to
experience spontaneously occuring traveling waves
of dominance
Click here to see a movie that simulates what
traveling waves of dominance can look like
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This is what your two eyes view
This is what you see
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Estimated wave speed within V1
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Functional magnetic resonance imaging in
retinotopically identified early visual areas
What is viewed in the scanner
Using a 3T scanner, haemodynamic responses are
measured while the observer views traveling waves
triggered within a radial grating initially
suppressed from awareness by interocular flash
suppression
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Predicted fMRI (BOLD) responses
Percept
Local contrast
FMRI signal
Time to peak amplitude
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V1 activity correlates with percept
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DN (n262)
PN (n100)
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Time to peak (s)
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SL (n151)
Average
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Distance from upper vertical meridian (cm)
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• Click here to see an animation showing
• 1. What an observer typically perceives on
  individual trials (right)
• 2. Evoked brain responses accompanying those
  perceptual
• waves of dominance (left).
• Note physical stimulation remains invariant
  after the trigger

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V1 wave latency correlates with perceived latency
Perceptual wave speed
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Average
of trials
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Time to peak (s)
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Latency (s)
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0
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Distance from upper vertical meridian (cm)
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Are Cortical Waves Observed when Attention is
Diverted?
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right eye
diverted
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attended
C
C
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display
Time to peak (s)
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C2DA3B42D...
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Distance from UVM in V1 (cm)
Task detect repetitions of a briefly presented
alphanumeric character, defined by form and
color, that could appear within a stream of
Colored letters and numbers
In V1, waves are slower and reduced in amplitude
(not shown) Waves are abolished in V2 and V3
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Summary

• fMRI responses in V1 are correlated with
  spatio-temporal dynamics of perceptual waves
  during binocular rivalry.
• The velocity of neural waves in V1 is correlated
  with the latency of perceptual waves.
• Neural waves in V1 are still present when
  attention is diverted, but the waves are weaker
  in amplitude and slower in velocity.
• Visual areas V2 and V3 also exhibit cortical
  waves of activity during rivalry but the waves
  are eliminated when attention is diverted

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References

• Lee, S.H., Blake, R. and Heeger, D. (2005)
  Traveling waves of activity in primary visual
  cortex during binocular rivalry. Nature
  Neuroscience, 8, 22 23.
• Lee, S-H., Blake, R. Heeger, D. (2007)
  Hierarchy of cortical responses underlying
  binocular rivalry. Nature Neuroscience. 10,
  1048-1054.
• Wilson, H.R., Blake, R. Lee, S.H. (2001)
  Dynmics of traveling waves in visual percepion.
  Nature, 412, 907-910.