Neural Correlates of Consciousness By Charlene Campbell

Neural Correlates of Neural Correlates of Consciousness Consciousness

By Charlene CampbellBy Charlene Campbell

Different Correlates of Different Correlates of Consciousness to be Consciousness to be AddressedAddressed

AuditionAudition– Neural Correlates of Novel sound gatingNeural Correlates of Novel sound gating

Jaaskelainen Jaaskelainen Perspective takingPerspective taking

– Neural Correlates of human self-consciousnessNeural Correlates of human self-consciousness Vogeley Vogeley et al. et al.

VisionVision– Neural Correlates of the attentional blinkNeural Correlates of the attentional blink

Feinstein Feinstein et alet al, Kranczioch , Kranczioch et alet al – Neural Correlates of Conscious VisionNeural Correlates of Conscious Vision

Pins and ffytchePins and ffytche

Neural Correlates Constituting Neural Correlates Constituting Novel Sounds to ConsciousnessNovel Sounds to Consciousness

Jaaskelainen et alJaaskelainen et al


Purpose:Purpose: Find the neural mechanisms that underlie Find the neural mechanisms that underlie

preattentive gating awareness of novel preattentive gating awareness of novel soundssounds


MethodsMethods Use fMRI, EEG, and MEG to show brain Use fMRI, EEG, and MEG to show brain

activity when auditory stimulation occurs activity when auditory stimulation occurs auditory stimuli auditory stimuli

Novel stimuliNovel stimuli

Give novel stimuli aloneGive novel stimuli alone Standard stimuliStandard stimuli

Give standard stimuli aloneGive standard stimuli alone Novel + Standard stimuliNovel + Standard stimuli

Give novel stimuli after standard stimulusGive novel stimuli after standard stimulus



ConclusionConclusion Neurons in posterior auditory cortex are more broadly Neurons in posterior auditory cortex are more broadly

tuned on sound frequency then that of anterior tuned on sound frequency then that of anterior auditory cortexauditory cortex

Processing of low-novel sounds is significantly Processing of low-novel sounds is significantly delayed in the anterior auditory cortexdelayed in the anterior auditory cortex

High-novel sounds are processed quickly and enter High-novel sounds are processed quickly and enter consciousness soon through stimulation of un-consciousness soon through stimulation of un-adapted feature-specific neurons within posterior adapted feature-specific neurons within posterior auditory cortexauditory cortex

Vogeley et alVogeley et al

Neural Correlates of First Person Neural Correlates of First Person Perspective as One Constituent of Human Perspective as One Constituent of Human Self-ConsciousnessSelf-Consciousness– PurposePurpose

To find the neural mechanisms associated with To find the neural mechanisms associated with perspective takingperspective taking

Vogeley Vogeley

MethodsMethods– A virtual seen consisting of an avatar and red balls in A virtual seen consisting of an avatar and red balls in

a room was presented by different camera viewpointsa room was presented by different camera viewpoints– View points were either 3PP vs 1PP or a ground view View points were either 3PP vs 1PP or a ground view

(gv) vs. an aerial view (av)(gv) vs. an aerial view (av)– Camera viewpoints presented to normal viewers in an Camera viewpoints presented to normal viewers in an

fMRI experimentfMRI experiment– Task of subjects:Task of subjects:

Count objects as seen either from avatars perspective (3pp) Count objects as seen either from avatars perspective (3pp) or from their own perspective (1pp)or from their own perspective (1pp)

Vogeley Vogeley et alet al


ResultsResults– When taking a 3PP, there was increased activity in When taking a 3PP, there was increased activity in

the precuneus, the frontal cortex bilaterally, the the precuneus, the frontal cortex bilaterally, the cerebellum bilaterally, the left temporal cortex, and cerebellum bilaterally, the left temporal cortex, and the occipitoparietal cortex on the left side.the occipitoparietal cortex on the left side.

– When taking a 1PP, there was increased activity in When taking a 1PP, there was increased activity in the lateral superior temporal cortex bilaterally the lateral superior temporal cortex bilaterally including the insula, mesial cortical areas (both frontal including the insula, mesial cortical areas (both frontal and parietal), left frontal coretex and the right and parietal), left frontal coretex and the right postcentral gyruspostcentral gyrus


ConclusionConclusion– Even though there are joint neural Even though there are joint neural

mechanisms, decision making 3PP and 1PP mechanisms, decision making 3PP and 1PP rely on differential neural processes.rely on differential neural processes.

First Neurobiological Accounts of First Neurobiological Accounts of Visual ConsciousnessVisual Consciousness

View 1View 1 Visual consciousness is a localized eventVisual consciousness is a localized event

• Zeki and ffytche showed that the difference in Zeki and ffytche showed that the difference in seeing or not seeing was dependent on the activity seeing or not seeing was dependent on the activity of a single visual area – area V5of a single visual area – area V5

View 2View 2 Visual consciousness is a network of inter-Visual consciousness is a network of inter-

related activityrelated activity• Lumer Lumer et alet al showed that perceptual transitions showed that perceptual transitions

between 2 constant stimuli correlated with activity between 2 constant stimuli correlated with activity in a fronto-parietal network of areas.in a fronto-parietal network of areas.

Consciousness as a NetworkConsciousness as a Network

Neural Correlates of the Attentional BlinkNeural Correlates of the Attentional Blink– Feinstein Feinstein et alet al– Kranczioch Kranczioch et alet al

Feinstein Feinstein et alet al

PurposePurpose– To understand the path from sensory To understand the path from sensory

processes to conscious perceptionprocesses to conscious perception


MethodsMethods– RSVP of numbers and lettersRSVP of numbers and letters

Embedded in RSVP are T1 and T2Embedded in RSVP are T1 and T2– T1 T1 either odd or even string of numbers (ex. 11111 or either odd or even string of numbers (ex. 11111 or

22222)22222)– T2 T2 either a neutral or aversive word either a neutral or aversive word

Subjects told to focus on RSVP and then state Subjects told to focus on RSVP and then state whether T1 was odd or even, and whether T2 was whether T1 was odd or even, and whether T2 was seen seen

fMRI’s were taken though out experimentfMRI’s were taken though out experiment



ResultsResults– (a) chart depicting the areas of the brain that (a) chart depicting the areas of the brain that

showed greater activity when T2 was showed greater activity when T2 was identifiedidentified

– (b) is another representation of an increase in (b) is another representation of an increase in activity when T2 was detectedactivity when T2 was detected

– (c) Shows how the anterior cingulate, (c) Shows how the anterior cingulate, frontopolar cortex, and the medial prefrontal frontopolar cortex, and the medial prefrontal cortex increase in activity and thus cortex increase in activity and thus consciously perceived T2 consciously perceived T2


Conclusions Conclusions – Activation of the anterior cingulate, medial Activation of the anterior cingulate, medial

prefrontal cortex, and frontopolar cortex is prefrontal cortex, and frontopolar cortex is involved in the conscious perception of T2involved in the conscious perception of T2

– Results support theory that consciousness is Results support theory that consciousness is a product of interactions between many parts a product of interactions between many parts of the brainof the brain

Kranczioch Kranczioch et alet al

– PurposePurposeIdentify brain regions assumed to be involved in Identify brain regions assumed to be involved in controlling the access of information to controlling the access of information to consciousnessconsciousness

– Relevant conclusions of previous studiesRelevant conclusions of previous studiesInterference between target and mask is Interference between target and mask is associated with increased activation of associated with increased activation of frontoparietal networkfrontoparietal network

– Includes lateral frontal, anterior cingulate, and Includes lateral frontal, anterior cingulate, and interparietal areasinterparietal areas


MethodsMethods– A RVSP sequence of 20 capital black letters and 1 capital green A RVSP sequence of 20 capital black letters and 1 capital green

letter were shown with no inter-stimulus intervalletter were shown with no inter-stimulus intervalRSVP=rapid serial visual presentationRSVP=rapid serial visual presentationThe capital green letter played the role of being a defined target that The capital green letter played the role of being a defined target that the subject should focus on. the subject should focus on. will be referred to as T1 (target 1)will be referred to as T1 (target 1)

– The letter X was then denoted as the second target The letter X was then denoted as the second target T2 T2– In the experiment, subjects were required to indicate after seeing In the experiment, subjects were required to indicate after seeing

the RSVP sequence if:the RSVP sequence if:T1 was a vowelT1 was a vowelT2 was presentT2 was present

– Responses given via a response padResponses given via a response pad


Methods Side NoteMethods Side Note– T1 and T2 target relations in previous studiesT1 and T2 target relations in previous studies

In an RSVP sequence when T2 followed T1 In an RSVP sequence when T2 followed T1 between 200-400ms later, the detection of T2 was between 200-400ms later, the detection of T2 was significantly impaired significantly impaired attentional blink window attentional blink window

Accuracy for T2 detection was highest when Accuracy for T2 detection was highest when immediately following T1 or at least 500 ms after immediately following T1 or at least 500 ms after T1 T1


Methods continuedMethods continued– fMRI’s were retrieved while sequence fMRI’s were retrieved while sequence

evaluation was taking placeevaluation was taking place


ResultsResults– 6 conditions were studied6 conditions were studied

– Lag refers to amount of time which T2 followed after T1Lag refers to amount of time which T2 followed after T1

T2 detected (lag 1T2 detected (lag 1 100ms after T1) 100ms after T1)

T2 detected (lag 2)T2 detected (lag 2)

T2 missed (lag 1)T2 missed (lag 1)

T2 missed (lag 2)T2 missed (lag 2)

T2 detectedT2 detected

No T2No T2


ResultsResults– (A) Regions of the (A) Regions of the

brain that were active brain that were active when T2 was detected when T2 was detected and when T2 was and when T2 was absentabsent

– (B) Regions of the (B) Regions of the brain that were active brain that were active when T2 was detected when T2 was detected and when T2 was and when T2 was missedmissed



ConclusionConclusion– Findings support that T2 is not detected Findings support that T2 is not detected

because it doesn’t reach working memorybecause it doesn’t reach working memory– Targets that do not reach awareness are Targets that do not reach awareness are

processed beyond a first stage of perceptual processed beyond a first stage of perceptual identificationidentification

Supported by findings of increased activity of Supported by findings of increased activity of inferior frontal, parietal, and frontal/anterior inferior frontal, parietal, and frontal/anterior cingulate cortex in the T2 cingulate cortex in the T2 missedmissed trials in trials in comparison to the T2 comparison to the T2 absentabsent trials trials


Purpose:Purpose:To Identify whether neural correlates of visual To Identify whether neural correlates of visual

consciousness are localized or distributed.consciousness are localized or distributed.To Identify where the neural correlates are To Identify where the neural correlates are

locatedlocated


Basic Ideas to keep in mind:Basic Ideas to keep in mind:Whether the stimulus is seen or not seen Whether the stimulus is seen or not seen

indicates a difference between visual input indicates a difference between visual input and visual perception.and visual perception.If stimulus is seen, then visual perception has If stimulus is seen, then visual perception has

taken placetaken placePerception for this experiment is defined as a Perception for this experiment is defined as a

“conscious visual experience”“conscious visual experience”


MethodsMethods Visual stimulus portrayedVisual stimulus portrayed

Visual stimulus is composed of a circular sinosoidal grating Visual stimulus is composed of a circular sinosoidal grating of ~1 cycle/degree appearing on a grayscale background.of ~1 cycle/degree appearing on a grayscale background.

Each stimulus trial is composed of 5 partsEach stimulus trial is composed of 5 parts Pre-stimulus warning soundPre-stimulus warning sound Pre-stimulus waiting period (random variations in length of Pre-stimulus waiting period (random variations in length of

period to ensure no pre-stimulus anticipatory response) period to ensure no pre-stimulus anticipatory response) Stimulus presentationStimulus presentation Post-stimulus warning soundPost-stimulus warning sound Post-stimulus waiting periodPost-stimulus waiting period

Every time the stimulus was seen, the participant was to Every time the stimulus was seen, the participant was to indicate so by pressing a buttonindicate so by pressing a button


Methods continuedMethods continuedFor each trial a fMRI (functional magnetic For each trial a fMRI (functional magnetic

resonance imaging) was simultaneously resonance imaging) was simultaneously taken.taken.16 axial slides parallel to the plane passing through 16 axial slides parallel to the plane passing through

the anterior and posterior commissures were taken the anterior and posterior commissures were taken every 2 sec per trialevery 2 sec per trial

For each trial a EP (evoked potential) was For each trial a EP (evoked potential) was simultaneously recorded as wellsimultaneously recorded as wellEP = neurophysiological components evoked by EP = neurophysiological components evoked by

the taskthe task


Results of fMRIResults of fMRIActivations:Activations:

Visual Areas:Visual Areas: Thalamus, striate cortex, fusiform gyrus, and medial Thalamus, striate cortex, fusiform gyrus, and medial

occipital lobeoccipital lobeMotor Related areas:Motor Related areas:

Left sensory motor cortexLeft sensory motor cortex Right cerebellar hemisphereRight cerebellar hemisphere Supplementary motor cortex in both hemispheresSupplementary motor cortex in both hemispheres

Auditory systemAuditory system Superior temporal gyrus bilaterally in the insulaSuperior temporal gyrus bilaterally in the insula


Results of fMRIResults of fMRISuppression:Suppression:

Supra-marginal gyrus (parietal)Supra-marginal gyrus (parietal)Posterior cingulate and parahippocampul gyrus Posterior cingulate and parahippocampul gyrus

(limbic)(limbic)In an extended region passing from supperior In an extended region passing from supperior

frontal sulcus through the medial frontal gyrus to frontal sulcus through the medial frontal gyrus to the anterior cingulate gyrusthe anterior cingulate gyrus


Pins and ffytchPins and ffytch

Results of EP recordings during taskResults of EP recordings during task Early componentsEarly components

High-contrast supra-threshold grating evoked a series of High-contrast supra-threshold grating evoked a series of positive and negative waves over OL and PLpositive and negative waves over OL and PL

Intermediate latency componentsIntermediate latency components Yes trials elicited a negativeYes trials elicited a negative

Maximal over left parietalMaximal over left parietal

Late componentsLate components A negative slow wave was present for yes trials but not for no A negative slow wave was present for yes trials but not for no

trials or catch trials. trials or catch trials. Maximal over left parietal lobeMaximal over left parietal lobe

Pins and ffytchPins and ffytch



ConclusionsConclusionsActivity correlating with consciousness is Activity correlating with consciousness is

distributed over timedistributed over timeSuggest that there is a segregation in primary Suggest that there is a segregation in primary

and secondary correlatesand secondary correlatesOL activity after stimulus presentation is likely to be OL activity after stimulus presentation is likely to be

the primary correlate of consciousness the primary correlate of consciousness PL, FL, motor and auditory regions are most likely PL, FL, motor and auditory regions are most likely

the secondary correlates of consciousnessthe secondary correlates of consciousness

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Neural Correlates of Consciousness By Charlene Campbell