Cortical Dynamics Underlying Waves of Perceptual Dominance

People Involved in this Project Randolph Blake Vanderbilt University David Heeger New York University Sang-Hun Lee Seoul National University Hugh Wilson York University

Binocular Rivalry -- a psychophysical tool for studying cortical dynamics left eyeright eye

Characteristics of Binocular Rivalry Dominance tends to be unitary when rival targets are small but piecemeal when targets are large Dominance tends to be unitary when rival targets are small but piecemeal when targets are large Successive phases of dominance are unpredictable in duration Successive phases of dominance are unpredictable in duration Visual adaptation plays a role in causing state changes Visual adaptation plays a role in causing state changes Reciprocal inhibition between feature detectors Self-adaptation, plus noise

dominance states over time Spatio-temporal dynamics during state transitions left eye right eye

left eye right eye wave-like transitions between dominance Spatio-temporal dynamics during state transitions

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 likehere

time This is what your two eyes view This is what you see

Wave speed measured psychophysically Estimated wave speed within V1

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

Predicted fMRI (BOLD) responses Percept FMRI signal BOLD response time Local contrast Neural activity time Time to peak amplitude

5 6 DN (n=262) PN (n=100) Distance from upper vertical meridian (cm) Time to peak (s) SL (n=151) Average V1 activity correlates with percept

Click here to see an animation showing:here 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

V1 wave latency correlates with perceived latency Average Latency (s) # of trials Time to peak (s) slow medium fast Distance from upper vertical meridian (cm) Perceptual wave speed

left eyeright eye Distance from UVM in V1 (cm) Time to peak (s) Are Cortical Waves Observed when Attention is Diverted? display C C2DA3B42D... 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 C time In V1, waves are slower and reduced in amplitude (not shown); Waves are abolished in V2 and V3 diverted 4 attended

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

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, Wilson, H.R., Blake, R. & Lee, S.H. (2001) Dynmics of traveling waves in visual percepion. Nature, 412,