Binocular RivalryBinocular RivalryThis tutorial provides an introductory This tutorial provides an introductory

exploration of binocular rivalry with a review of exploration of binocular rivalry with a review of

some theoretical concepts and important some theoretical concepts and important

research relevant to the field. research relevant to the field.

For more tutorials on visual perception visitFor more tutorials on visual perception visit

viper2go on the Viper website www.viperlib.comviper2go on the Viper website www.viperlib.com

Olivia Carter (2006)

When faced with ambiguous visual information you normally don’t When faced with ambiguous visual information you normally don’t

experience a combination of the different interpretations. Instead, experience a combination of the different interpretations. Instead, you you

will will seesee only one interpretation. After time, only one interpretation. After time, your perception will begin to your perception will begin to

switchswitch between each of the competing (“rivalling”) alternatives. between each of the competing (“rivalling”) alternatives.

The images that cause this The images that cause this Perceptual RivalryPerceptual Rivalry have a few names:have a few names:

- Ambiguous - Ambiguous

- Bistable/multistable- Bistable/multistable

- Rivalrous- Rivalrous

old / young woman

2 faces /1 face behind candle

Blue face of cubeFront / back

Slide 1

right eyeimage

left eye image

Binocular RivalryBinocular Rivalry is a type of perceptual rivalry. When is a type of perceptual rivalry. When

two different images are presented to the two eyes two different images are presented to the two eyes

simultaneously, you are only conscious of one of the simultaneously, you are only conscious of one of the

two images at a time.two images at a time. - one is - one is dominantdominant, the other is , the other is suppressedsuppressed

- every few seconds the perceptual - every few seconds the perceptual

dominance will dominance will switchswitch

Slide 2

During Binocular rivalry all/part of one image appears totally During Binocular rivalry all/part of one image appears totally

suppressed from consciousness. suppressed from consciousness.

- To experience this suppression yourself- To experience this suppression yourself 1) roll up some paper like a telescope. 1) roll up some paper like a telescope.

2) look through it with your right eye & put your left hand next to the paper 2) look through it with your right eye & put your left hand next to the paper

roll a few inches in front of your left eyeroll a few inches in front of your left eye

The image seen through the paper roll The image seen through the paper roll

will suppress a section of the hand.will suppress a section of the hand.

Note:Note: The hand will generally stay suppressed The hand will generally stay suppressed

because it is the “weaker stimulus” (the images because it is the “weaker stimulus” (the images

need to be “equal strength” for rivalry – if you hold need to be “equal strength” for rivalry – if you hold

still and face a blank wall you might get rivalry still and face a blank wall you might get rivalry

between the wall and hand in the central patch). between the wall and hand in the central patch).

Slide 3

Turn your flesh into beerTurn your flesh into beer …. If you are very bored you …. If you are very bored you

can even experience rivalry at the pub!!can even experience rivalry at the pub!!

All you need is &All you need is &

Note:Note: The beer will always win !! The beer will always win !!

Slide 4

Why is binocular rivalry interesting? Why is binocular rivalry interesting? Each image is constantly presented but every few seconds Each image is constantly presented but every few seconds we switch from being conscious to unconscious of the we switch from being conscious to unconscious of the imageimage

… … if we can identify what is different about the brain when if we can identify what is different about the brain when someone is conscious vs unconscious of the image, we someone is conscious vs unconscious of the image, we may have solved one of the biggest questions left in may have solved one of the biggest questions left in science….science….

*** The *** The BIGBIG question *** question ***

How does the brain generate conscious experience?How does the brain generate conscious experience?

- the search for a neural correlate of consciousness (NCC).- the search for a neural correlate of consciousness (NCC).

The Answer …??The Answer …??

……Lots of ideas from philosophy, but no evidence from science yet!! Lots of ideas from philosophy, but no evidence from science yet!!

Slide 5

A few smaller questions…A few smaller questions…

1)1) At what level of processing is the “competition” between the At what level of processing is the “competition” between the images resolved? … Early or Late?images resolved? … Early or Late?

2) 2) Which stimulus factors influence perceptual dominance? Which stimulus factors influence perceptual dominance?

3)3) How much information can be processed “unconsciously”? How much information can be processed “unconsciously”?

4)4) What is driving the switches in perception? What is driving the switches in perception?

The Answer …. some ideas discussed in next few slides….The Answer …. some ideas discussed in next few slides….

Slide 6

At what level of processing is the “competition” At what level of processing is the “competition” between the images resolved?between the images resolved?

`

It has been proposed that binocular rivalry is resolved It has been proposed that binocular rivalry is resolved EARLYEARLY in the visual pathway, resulting from mutual inhibition between in the visual pathway, resulting from mutual inhibition between monocular neurons in primary visual cortex (V1)monocular neurons in primary visual cortex (V1) (Blake, 1989) (Blake, 1989)

-- In other words, each EYE’s image is alternately suppressed. In other words, each EYE’s image is alternately suppressed.

Supporting evidenceSupporting evidence-Using fMRI, neural activity was found to change in time with -Using fMRI, neural activity was found to change in time with perception in monocular regions of V1 perception in monocular regions of V1 (Tong & Engle, 2001; Polonsky et al, 2000)(Tong & Engle, 2001; Polonsky et al, 2000)

- When the images being presented to the dominant and - When the images being presented to the dominant and suppressed eye are interchanged, observers will continue suppressed eye are interchanged, observers will continue seeing with the dominant eye - causing the previously seeing with the dominant eye - causing the previously suppressed image to become dominant suppressed image to become dominant (Lee & Blake, 2004; Blake et al, 1980)(Lee & Blake, 2004; Blake et al, 1980)

Slide 7

`

Continued….Continued….

HOWEVERHOWEVER evidence also suggest that rivalry is resolved evidence also suggest that rivalry is resolved LATELATE (in higher cortical) areas after information from the two (in higher cortical) areas after information from the two eyes has been integrated. – eyes has been integrated. – rivalry between imagesrivalry between images

For exampleFor exampleNormal, coherent rivalry dominance (2sec) will be seen if…Normal, coherent rivalry dominance (2sec) will be seen if…

- the eye of presentation is swapped quickly (200ms) the eye of presentation is swapped quickly (200ms) (Logothetis et al., 1996)(Logothetis et al., 1996)

Colour and motion cues from two competing rivalry stimulus Colour and motion cues from two competing rivalry stimulus can be decoupled &/or integrated independently can be decoupled &/or integrated independently (Carney et al, 1987; (Carney et al, 1987;

Carson & He, 2000)Carson & He, 2000)

PERCEPT

Left eye Right eye

RIVALRY STIMULUS- you present correspondingyou present corresponding patchwork images to eachpatchwork images to each eye (see figure) eye (see figure) (Kovaks et al, 1996)(Kovaks et al, 1996)

Slide 8

`

Continued….Continued….

Electrophysiology experiments in monkeys show that the Electrophysiology experiments in monkeys show that the proportion of neurons firing in time with perception increases proportion of neurons firing in time with perception increases at higher levels of processingat higher levels of processing (Logothetis & Schall, 1989;(Logothetis & Schall, 1989; Leopold et al., 1996)Leopold et al., 1996)

>> Together these results suggest a hierarchy of competition >> Together these results suggest a hierarchy of competition at multiple levels of processing.at multiple levels of processing.

At what level of processing is the “competition” At what level of processing is the “competition” between the images resolved?between the images resolved?

Neural activity is recorded while, monkey reports what it sees.

Neuron is active, only when it reports one of the two percepts. More neural activity correlates with

perception at later stages of processing.

Slide 9

Which stimulus factors influence perceptual dominance?Which stimulus factors influence perceptual dominance?

Salience also makes a difference!Salience also makes a difference!For example, an upright faces will dominate over an upside down or a For example, an upright faces will dominate over an upside down or a

garbled facegarbled face (Engel, 1956; Yu & Blake, 1992)(Engel, 1956; Yu & Blake, 1992)

Note: the image through the paper role (shown on previous Note: the image through the paper role (shown on previous slides) dominates most of the time because it generally has slides) dominates most of the time because it generally has more motion and salience cues.more motion and salience cues.

50%

50%

MOREImage 1

Image 2 Image 2

“Stronger” Image 1

Dominance Time Dominance Time

Bias in perceptual dominance

Bias in perceptual dominance

2 sec2 sec2 sec

2 sec 2 sec 2 sec 2 sec 2 sec 2 sec

1 sec 1 sec 1 sec

Stimulus “strength”Stimulus “strength” Increasing the strength of one stimulus, by adding motionIncreasing the strength of one stimulus, by adding motion or contrast etc.., or contrast etc.., will will increaseincrease its its dominancedominance by by decreasingdecreasing the duration of its the duration of its suppressionsuppression - - This is sometimes termed Levelt’s 2nd proposition.This is sometimes termed Levelt’s 2nd proposition.(Breese, 1909; Mueller & Blake, 1989; Levelt, 1965) (Breese, 1909; Mueller & Blake, 1989; Levelt, 1965)

or

“stronger”

LESS

Slide 10

continued…continued…

Context Context Addition of a contextual background will Addition of a contextual background will increase predominance of the increase predominance of the inconsistentinconsistent target target (Fukuda & Blake, 1992; Carter et al., 2004)(Fukuda & Blake, 1992; Carter et al., 2004)

Left eye

Dominant

Right eye

Suppressed

>

NOTE:NOTE: In this context effect, dominance is increased due to In this context effect, dominance is increased due to increaseincrease in in dominance phasedominance phase duration (“anti-Levelt” effect).duration (“anti-Levelt” effect).

50%

50%

MOREImage 1

Image 2 Image 2

“Stronger” Image 1

Dominance Time Dominance Time

Bias in perceptual dominance

Bias in perceptual dominance

2 sec2 sec2 sec

2 sec 2 sec 2 sec 3 sec

2 sec 2 sec 2 sec

3 sec 3 sec

LESS

Which stimulus factors influence perceptual dominance?Which stimulus factors influence perceptual dominance? Slide 11

continued…continued…

GroupingGroupingMotion, orientation and other gestalt cues can promote Motion, orientation and other gestalt cues can promote synchronised dominancesynchronised dominance of multiple “ of multiple “groupedgrouped” targets. ” targets. (Alais & Blake, 1999; Sobel & Blake, 2002)(Alais & Blake, 1999; Sobel & Blake, 2002)

+

++

+

Left eye Right eye

Collinear gratings group - they come

& go together

Orthogonal gratings don’t group - they

come & go independently

+ + +`+

+ + ++

TIME

PERCEPTRIVALRY STIMULUS

Which stimulus factors influence perceptual dominance? Which stimulus factors influence perceptual dominance? Slide 12

What information can be processed “unconsciously”?What information can be processed “unconsciously”?

Adaptation after-imagesAdaptation after-images....Aftereffects from adaptation to Aftereffects from adaptation to orientationorientation, , spatial frequencyspatial frequency and and motionmotion cues, can be generated by cues, can be generated by suppressed suppressed stimulus. stimulus. (Wade & Wenderoth, 1978; Lehmkuhle & Fox, 1976; Blake & Fox, 1974)(Wade & Wenderoth, 1978; Lehmkuhle & Fox, 1976; Blake & Fox, 1974)

Dominant Suppressed

or

Non-face image

neutralface

emotionalface

Emotional cuesEmotional cuesThe amygdala shows greater fMRI response to The amygdala shows greater fMRI response to fearfulfearful and and happy happy faces relative to neutral faces, even during periods of faces relative to neutral faces, even during periods of suppression.suppression. (Williams et al., 2004)(Williams et al., 2004)

Information about emotion can be Information about emotion can be processed “unconsciously.”processed “unconsciously.”

Slide 13

Factors determining switch rate Factors determining switch rate

Stimulus & AttentionStimulus & Attention

Aside from changing stimulus strength, a number of other factors can Aside from changing stimulus strength, a number of other factors can influence rivalry switch rate. For example, rivalry switching will become influence rivalry switch rate. For example, rivalry switching will become slower if: slower if:

1) The rivalry stimulus is moved relative to the eye 1) The rivalry stimulus is moved relative to the eye (Blake et al, 2003)(Blake et al, 2003)

2) The rivalry stimulus is presented intermittently – on for a few 2) The rivalry stimulus is presented intermittently – on for a few seconds, off for a few seconds seconds, off for a few seconds (Leopold et al., 2002)

3) The observer attends to some feature of the dominant target 3) The observer attends to some feature of the dominant target (Lack, 1978)(Lack, 1978)

Differences between peopleDifferences between people

1) There is a huge degree of 1) There is a huge degree of variabilityvariability in switch rate across the in switch rate across the population. However, within an individual the switch rate is quite stable population. However, within an individual the switch rate is quite stable and and correlatedcorrelated across different types of perceptual rivalries across different types of perceptual rivalries (Carter & Pettigrew, (Carter & Pettigrew, 2003)2003)

2) People with 2) People with bipolar disorderbipolar disorder show slower than normal switching show slower than normal switching (Pettigrew & Miller, 1998).(Pettigrew & Miller, 1998).

Slide 14

Multiple stages of Multiple stages of mutual inhibitionmutual inhibition between between neural populations coding for the competing neural populations coding for the competing images features. The neurons generating the images features. The neurons generating the dominant image inhibit the neurons dominant image inhibit the neurons corresponding to the suppressed image, but corresponding to the suppressed image, but over time the system fatigues and the strength over time the system fatigues and the strength of inhibition reduces allowing the suppressed of inhibition reduces allowing the suppressed image to become dominant... This processes image to become dominant... This processes

continues indefinitely.continues indefinitely. (Blake, 1989; Wilson et al, 2001)(Blake, 1989; Wilson et al, 2001)

What is driving the switch in perception? What is driving the switch in perception?

OROR

The perceptual switches are generated by The perceptual switches are generated by an an oscillatoroscillator external to the level of visual external to the level of visual representation. It has been proposed that representation. It has been proposed that oscillatory activity in the brainstem may oscillatory activity in the brainstem may generate rhythmic fluctuations in activity generate rhythmic fluctuations in activity throughout the brain. The perceptual throughout the brain. The perceptual switches may be driven by these oscillations switches may be driven by these oscillations (Pettigrew, 2001) (Pettigrew, 2001)

or

Slide 15

Some unusual facts about rivalry Some unusual facts about rivalry

MeditationMeditation - Tibetan Buddhist monks can - Tibetan Buddhist monks can slow and even stop the binocular rivalry slow and even stop the binocular rivalry switching during a focused style of switching during a focused style of meditation called “one-point.”meditation called “one-point.” (Carter et al, 2005c)(Carter et al, 2005c)

PsilocybePsilocybe mushrooms mushrooms PsilocybinPsilocybin

Hallucinogenic drugsHallucinogenic drugs – A study using psilocybin (the active – A study using psilocybin (the active compound in “magic mushrooms) found that the speed of compound in “magic mushrooms) found that the speed of binocular rivalry switching binocular rivalry switching can be reliably slowed, can be reliably slowed, in proportion to the drug’s in proportion to the drug’s affects on attention affects on attention & arousal & arousal (Carter et al, 2005a&b)(Carter et al, 2005a&b)

Slide 16

Further Reading - References Further Reading - References General Reviews General Reviews - - Alais, D & Blake, R. (2005) Binocular rivalry. MIT Press, Cambridge, MABlake R., Logothetis N.K. (2002) Visual competition. Nat Rev Neurosci 3: 13-21.Logothetis N.K. (1998) Single units and conscious vision Phil Trans R Soc Lond B 353: 1801-1818Leopold D.A., Logothetis N.K. (1999) Multistable phenomena: changing views in perception. Trends Cogn Sci 3: 254-264.

Influential Studies Influential Studies --Blake R. (1989) A neural theory of binocular rivalry. Psychol Rev 96: 145-67.Kovacs I., Papathomas T.V., Yang M., Feher A. (1996) When the brain changes its mind: interocular grouping during binocular rivalry. Proc Nat Acad Sci U S A 93: 15508-11.Leopold D.A., Logothetis N.K. (1996) Activity changes in early visual cortex reflect monkeys' percepts during binocular rivalry. Nature 379: 549-53.Leopold D.A., Wilke, M., Maier, A. & Logothetis N.K. (2002) Stable perception of visually ambiguous patterns. Nature Neuroscience 5: 605-9Levelt, W. (1965) On binocular rivalry. Muton, The Hague.Logothetis N.K., Leopold D.A., Sheinberg D.L. (1996) What is rivalling during binocular rivalry? Nature 380: 621-4.Lumer E.D., Friston K.J., Rees G. (1998) Neural correlates of perceptual rivalry in the human brain. Science 280: 1930-4.Pettigrew J.D., Miller S.M. (1998) A 'sticky' interhemispheric switch in bipolar disorder? Proc R Soc Lond B Biol Sci 265: 2141-8. Tong F. & Engle S. A. (2001) Interocular rivalry revealed in the human blind-spot representation. 411: 195-9Tong F., Nakayama K., Vaughan J.T., Kanwisher N. (1998) Binocular rivalry and visual awareness in human extrastriate cortex. Neuron 21: 753-9.Wheatstone C. (1838) On some remarkable, and hitherto unobserved, phenomena of binocular vision. Philos Trans R Soc Lond 128: 371-394Wilson H.R., Blake R., Lee S.H. (2001) Dynamics of travelling waves in visual perception. Nature 412: 907-10.

Slide 17

Tutorial References Tutorial References List of papers mentioned in tutorial but not referenced on previous slideList of papers mentioned in tutorial but not referenced on previous slide --Alais, D., Blake, R. (1999) Grouping Visual features during binocular rivalry. Vision Res 39: 4341-53Blake, R. & Fox, R. (1974) Adaptation to ‘invisible’ gratings and the site of binocular rivalry suppression. Nature 249: 488-90Blake, R., Sobel, K. & Gilroy, L (2003) Visual motion retards alternations between conflicting perceptual interpretations. Neuron 39: 869-78 Blake, R., Westendorf, D. H. Overton, R. (1980) What is suppressed during binocular rivalry? Perception 9: 223-31Breese, B. B. (1909) Binocular Rivalry. Psychol Rev 16: 410-15Engel, E. (1956) The role of content in binocular resolution. Am J Psychology 69: 87-9Fukuda, H. Blake, R. (1992) Spatial interactions in binocular rivalry. J Exp Psychol Hum Percept Perform 18: 362-70Carlson,T. & He, S. (2000) Visible binocular beats from invisible monocular stimuli during binocular rivalry Current Biol 10: 1055-58Carney, T., Shadlen, M. & Switkes, E. (1987) Parallel processing of motion and colour information Nature 328: 647-9Carter, O. L., Campbell, T. G., Liu, G. B. & Wallis, G. M. (2004) Contradictory influence of context on predominance during binocular rivalry.  Clin Exp Optom 87 (3): 153-62.Carter, O. & Pettigrew, J. (2003) A Common Oscillator for Perceptual Rivalries? Perception 32 (3): 295-305 Carter, O. L., Pettigrew, J. D., Hasler, F. & Wallis, G. M., Liu, G. B., Hell, D., & Vollenweider, F. X. (2005a) Modulating the rate and rhythmicity of perceptual rivalry alternations with the mixed 5-HT2A and 5-HT1A agonist psilocybin. Neuropsychopharmacology 30: 1154-62Carter, O. L, Pettigrew, J. D., Hasler, F. & Wallis, G. M., Liu, G. B. & Vollenweider, F. X. (2005b) The brainstem and binocular rivalry: The role of serotonin in perceptual switching. (submitted). Carter, O., Presti, D., Callistemon, C., Liu, G. B., Ungerer, Y. & Pettigrew, J. D. (2005c) Meditation Alters Perceptual Rivalry in Tibetan Buddhist Monks. Current Biol 15(11): R412-3Kovacs, I., Papathomas, T., Yang, M. & Feher, A. (1996) When the brain changes its mind: Interocular grouping during binocular rivalry. Proc Nat Acad Sci 93: 15508-11.Lack, L. (1978) Selective attention and the control of binocular rivalry. Mouton, The Hague.Lee, S. H. & Blake, R. (2004) A fresh look at interocular grouping during binocular rivalry. Vision Res 44: 983-91Lehmkuhle, S. & Fox, R. (1976) Effect of binocular rivalry suppression on the motion aftereffect. Vision Res. 15: 855-9.Logothetis, N. K. & Shall, J. D. (1989) Neuronal correlates of subjective visual perception. Science 245: 761-763Pettigrew, J. D. (2001) Searching for the switch: Neural bases for perceptual rivalry alternations. Brain and Mind 2: 85-118Polonsky, A., Blake, R., Braun, J. & Heeger, D. Neuronal activity in human primary visual cortex correlates with perception during binocular rivalry Nature Neuroscience 3: 1153-9Mueller, T. J. & Blake, R. (1989) A fresh look at the temporal dynamics of binocular rivalry. Biol Cybern 61, 223-32Sobel, K. & Blake, R. (2002) How context influences predominance during binocular rivalry. Perception 31: 813-24Wade, N. & Wenderoth, P. (1978) The influence of colour and contour rivalry on the magnitude of the tilt aftereffect. Vision Res 18: 827-36.Williams, M., Morris, A., McGlone, F., Abbott, D. & Mattingley (2004) Amygdala responses to fearful and happy facial expressions under conditions of binocular suppression. The Journal of Neuroscience. 24: 2898-04Yue, K. & Blake, R. (1992) Do recognizable figures enjoy an advantage in binocular rivalry? J Exp Psychology: Human Perception and Performance. 18: 1158-73

Slide 18