frontiers in consciousness research tom de graaf dept of cognitive neuroscience, faculty of...

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.

16th century science:

Kallionates & Luu, 2005

Aristotle

Aristotle Galen

What is necessary for consciousness?

Press the Heart Cut the Brain

Galen

Consciousness in the brain? LEVELS

Seeing

Hearing

Feeling

Taste/smell

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

1.

How do you study consciousness?

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


Illusions

Illusory brightness, size, contours

Hallucinations etc.

What do you see?

What do you see?What do you see?

Exercise

A = B ?

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




ON-OFF paradigm




Ambiguous stimuli


Illusions


Hallucinations etc.

Left or right?Left or right?


Necker cube Face/Vase

Exercise: imagine…

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!




ON-OFF paradigm




Ambiguous stimuli


Illusions


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


WordsWords

Dehaene et al., 2001, nat neurosc


Houses>FacesHouses>Faces

Moutoussis & Zeki 2002, PNAS

The frontoparietal mysteryThe frontoparietal mystery

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

Transcraniale magnetische stimulatie Transcraniale magnetische stimulatie (TMS)(TMS)

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

I

M

E

+/- 80 to 100 ms after a stimulus, a TMS pulse over V1 can make you unconscious

Amassian et al., 1989

You in Your BodyYou in Your Body

Out-of-Body Experience

Blanke et al, Nature, 2002

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

The new Frontier:

Information Integration Theory

Tononi (& Edelman)

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


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


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

frontiers in consciousness research tom de graaf dept of cognitive neuroscience, faculty of...

Documents