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Frontiers in Consciousness Research
Tom de Graaf
Dept of Cognitive Neuroscience, Faculty of Psychology & Neuroscience, Maastricht University
Aristotle(from De motu animalium, 4th century B.C.)
The seat of the soul … - in fact, of nervous functions in general, - is to be sought in the heart. The brain is an organ of minor importance.
And of course, the brain is not responsible for any of the sensations at all. The correct view is that the seat and source of sensation is the region of the heart.
The visual system: some of its parts and connections
Felleman & Essen (1991), Cerebral cortex
Consciousness in the brain? LEVELS
Consciousness Research
State of Affairs: Neural Correlates of Unconsciousness Neural Correlates of ConsciousnessManipulating Consciousness (TMS)
Frontiers: Oscillations in the Brain
What are we talking about?
Self awareness
Higher-order awareness
Medical awareness
“Consciousness”
ExperienceAccess consciousness
Phenomenal consciousness
De Graaf & Sack (in preparation)
HARD PROBLEM ?
What are the problems?
Color changing card trick Blindsight
Many different kinds of problems, we focus on conscious vs unconscious vision
Watching the Conscious Brain
Functional Magnetic Resonance Imaging
(fMRI)
What is happening inside the brain?
3T MRI scanner, at FPN in Maastricht
Regional brain activity
The special problem of ‘scanning The special problem of ‘scanning conscious perception’conscious perception’
Separating Conscious from Separating Conscious from Unconscious VisionUnconscious Vision
Conscious:
Blue, pink, orange, pretty, “I feel all warm and glowy…”
Unconscious:
Wavelengths, contrasts, associations: “what the hell am I doing here?”
Separating Conscious from Separating Conscious from Unconscious VisionUnconscious Vision
Conscious: “apple-ness”Conscious: “apple-ness” Conscious: “pear-ness”Conscious: “pear-ness”
Unconscious: 650 nm, shape,Unconscious: 650 nm, shape, Unconscious: 510 nm, Unconscious: 510 nm, orientationsorientations shape, orientationsshape, orientations
Ways to separate conscious vision Ways to separate conscious vision from unconscious visionfrom unconscious vision
Change the conscious experienceChange the conscious experience, keep , keep constant the incoming stimulationconstant the incoming stimulationConscious VisionConscious Vision
Change the incoming stimulationChange the incoming stimulation, keep , keep constant the conscious experienceconstant the conscious experienceUnconscious VisionUnconscious Vision
Research Paradigmsfor NCC and NCU
Multistable Perception
Binocular rivalry(monocular rivalry)(pattern rivalry)
ON-OFF paradigm
Strong ON-OFF(perception depends on background variables)
Weak ON-OFF(experimenter determines perception by experimental manipulation)
OFF-baseline Continuous flash suppression
Ambiguous stimuli
De Graaf & Sack (in preparation)
Illusions
Illusory brightness, size, contours
Hallucinations etc.
A brain experimentA brain experiment
A: real contour
B: illusory contour
C: no contour
Von der Heydt, Science, 1984
A brain experiment
A: real contour
B: illusory contour
C: no contour
Neurons in the brain (in early visual cortex) fire in response to contours, whether they are real or not.
Von der Heydt, Science, 1984
Neural Correlates of Neural Correlates of ConsciousnessConsciousness
AuditoryAuditory
HallucinationsHallucinations
Dierks et al., Neuron, 1999
Neural Correlates of Neural Correlates of ConsciousnessConsciousness
Supernumerary phantom limbSupernumerary phantom limb
Khateb et al., 2009
Illusions and the like: summaryIllusions and the like: summary
The brain The brain constructsconstructs our percept: our percept: it does not come cleanly from the outside!!it does not come cleanly from the outside!!
Opportunities for consciousness researchersOpportunities for consciousness researchers
Research Paradigmsfor NCC and NCU
Multistable Perception
Binocular rivalry(monocular rivalry)(pattern rivalry)
ON-OFF paradigm
Strong ON-OFF(perception depends on background variables)
Weak ON-OFF(experimenter determines perception by experimental manipulation)
OFF-baseline Continuous flash suppression
Ambiguous stimuli
De Graaf & Sack (in preparation)
Illusions
Illusory brightness, size, contours
Hallucinations etc.
Bistable perception: summaryBistable perception: summary
If one and the same experimental situation If one and the same experimental situation gives rise to two or more conscious gives rise to two or more conscious percepts percepts THAT CHANGE OVER TIMETHAT CHANGE OVER TIME……
Opportunity for consciousness researchers!Opportunity for consciousness researchers!
Research Paradigmsfor NCC and NCU
Multistable Perception
Binocular rivalry(monocular rivalry)(pattern rivalry)
ON-OFF paradigm
Strong ON-OFF(perception depends on background variables)
Weak ON-OFF(experimenter determines perception by experimental manipulation)
OFF-baseline Continuous flash suppression
Ambiguous stimuli
De Graaf & Sack (in preparation)
Illusions
Illusory brightness, size, contours
Hallucinations etc.
Neural Correlates of Neural Correlates of UnconsciousnessUnconsciousness
How do we know there is such a thing as How do we know there is such a thing as unconscious visionunconscious vision??Brain damage (special brains)Brain damage (special brains)
BlindsightBlindsightNeglectNeglect
BlindsightBlindsight
PresencePresence ColourColour DirectionDirectionLocationLocation OrientationOrientation DiscriminationDiscrimination
Neural Correlates of Neural Correlates of UnconsciousnessUnconsciousness
How do we know there is such a thing as How do we know there is such a thing as unconscious visionunconscious vision??Brain damage (special brains)Brain damage (special brains)
BlindsightBlindsightNeglectNeglect
Behavioral studies (normal brains)Behavioral studies (normal brains)Masking-primingMasking-priming
LocationLocation Word meaningWord meaning Number senseNumber sense
Opportunity for consciousness researchers!Opportunity for consciousness researchers!
What brain activations remain WITHOUT What brain activations remain WITHOUT conscious perception?conscious perception?
NCU – neural correlates of NCU – neural correlates of unconsciousnessunconsciousness
OrientationOrientation
Haynes & Rees 2005, nat neurosc
NCU – neural correlates of NCU – neural correlates of unconsciousnessunconsciousness
WordsWords
Dehaene et al., 2001, nat neurosc
NCU – neural correlates of NCU – neural correlates of unconsciousnessunconsciousness
Houses>FacesHouses>Faces
Moutoussis & Zeki 2002, PNAS
Conscious versus unconscious Conscious versus unconscious perception: summaryperception: summary
When conscious percept changes, activity in When conscious percept changes, activity in higher (extrastriate) visual areas changeshigher (extrastriate) visual areas changes
A A frontoparietal networkfrontoparietal network is involved, when is involved, when conscious percept changesconscious percept changes
Connectivity between extrastriate areas and the Connectivity between extrastriate areas and the frontoparietal network seems importantfrontoparietal network seems important
Magnetic tricks on consciousnessMagnetic tricks on consciousness
TTranscranial ranscranial MMagnetic agnetic SStimulation (timulation (TMSTMS))
Functional RelevanceFunctional Relevance
Stay-at-home messageStay-at-home message
TMS can manipulate the brain (with TMS can manipulate the brain (with observable effects)observable effects)
Can TMS manipulate consciousness..?Can TMS manipulate consciousness..?
Creating Unconsciousness Creating Unconsciousness
123
324
523
654
ABY
234
543
123
765
T
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+/- 80 to 100 ms after a stimulus, a TMS pulse over V1 can make you unconscious
Amassian et al., 1989
Consciousness Consciousness and and
connectivityconnectivity
Massimini et al., Science, 2005
TMS + EEG:
When conscious, the effect of a TMS pulse spreads much further:
The brain is ‘more connected’!
TMS: summaryTMS: summary
TMS CAN manipulate consciousnessTMS CAN manipulate consciousnessThus it CAN teach us about the locations Thus it CAN teach us about the locations
and timing of conscious processingand timing of conscious processing
Early visual cortex is important around 100 Early visual cortex is important around 100 ms.ms.
Probably a kind of feedback signal is Probably a kind of feedback signal is arriving by that timearriving by that time
Connectivity is key?Connectivity is key?
The interesting case of Neglect…The interesting case of Neglect… Widespread synchronization (EEG)Widespread synchronization (EEG) Working memory hypothesisWorking memory hypothesis Global neuronal workspaceGlobal neuronal workspace Global availabilityGlobal availability
Information Integration TheoryInformation Integration Theory Consciousness =Consciousness =
The amount of information integratedThe amount of information integrated
Observations:Observations: Our conscious percept is unified (one)Our conscious percept is unified (one) Our conscious percept is differentiated (many possible percepts)Our conscious percept is differentiated (many possible percepts)
A system that is conscious consists of many “nodes” with A system that is conscious consists of many “nodes” with complex connections between themcomplex connections between them
Notice: Notice: this system is not necessarily a brain, although our brain is one this system is not necessarily a brain, although our brain is one such systemsuch system
Φ
Tononi PMC 2003
Information Integration TheoryInformation Integration Theory
You versus a photodiodeYou versus a photodiode
Not enough possible states (too little information)Not enough possible states (too little information)
You versus a digital camera (1 Megapixel)You versus a digital camera (1 Megapixel)
Independent nodes (too little integration)Independent nodes (too little integration)
Tononi PMC 2003
Information Integration TheoryInformation Integration Theory The more complexity, The more complexity,
the more information the more information integration, integration, the more consciousnessthe more consciousness
Complexity
Information Integration
Tononi PMC 2003
Information Integration TheoryInformation Integration Theory
IIT allows IIT allows quantificationquantification of of consciousnessconsciousness
(compare “b” to “a”: it’s not only (compare “b” to “a”: it’s not only about the number of connections)about the number of connections)
So what about the brain?So what about the brain?
Tononi PMC 2003
Information Integration TheoryInformation Integration Theory The brain consists of many many The brain consists of many many
many many many many many many many many many many many many many many many many many many many many many many nodesmany many nodes
Over time, the effective Over time, the effective connections changeconnections change
The most complex whole of The most complex whole of connected nodes at any given connected nodes at any given time is the time is the main complexmain complex
A A dynamic core dynamic core consists of the consists of the thalamus and certain cortical thalamus and certain cortical regions – that as a whole interact regions – that as a whole interact more among the nodes in this more among the nodes in this core than with the rest of the core than with the rest of the brainbrain
The main complex or dynamic The main complex or dynamic core core are are consciousness consciousness
Tononi PMC 2003
Information Integration TheoryInformation Integration TheorySummary:Summary:
A conscious system needs both strong differentiation and strong integrationA conscious system needs both strong differentiation and strong integration A dynamic core of nodes in the brain forms consciousness at any point in time A dynamic core of nodes in the brain forms consciousness at any point in time
(changing)(changing)
Cognition BiologyCognition Biology
Evidence: Evidence: (predictions)(predictions) The brain should be in a more complex, integrated state during consciousness The brain should be in a more complex, integrated state during consciousness
than during unconsciousness (e.g. sleep)than during unconsciousness (e.g. sleep)
Regions implicated in consciousness should be highly connected to other parts Regions implicated in consciousness should be highly connected to other parts of the brain (e.g. prefrontal, thalamus)of the brain (e.g. prefrontal, thalamus)
Any complex system should, in principle, be conscious if enough information Any complex system should, in principle, be conscious if enough information integration occurs (e.g. future robots) integration occurs (e.g. future robots)
Tononi PMC 2003
Information Integration TheoryInformation Integration Theory
Evidence from simultaneous TMS/EEG:Evidence from simultaneous TMS/EEG:
A TMS pulse spreads further during wakefulness than during NREM A TMS pulse spreads further during wakefulness than during NREM sleepsleep
REM sleep (dreaming) resembles wakefulnessREM sleep (dreaming) resembles wakefulness
More integration during consciousness than non-consciousness!
Massimini et al., 2005 Science