Neural Correlates of Consciousness

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Neural Correlates of Consciousness

• By Charlene Campbell

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Different Correlates of Consciousness to be
Addressed

• Audition
• Neural Correlates of Novel sound gating
• Jaaskelainen
• Perspective taking
• Neural Correlates of human self-consciousness
• Vogeley et al.
• Vision
• Neural Correlates of the attentional blink
• Feinstein et al, Kranczioch et al
• Neural Correlates of Conscious Vision
• Pins and ffytche

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Neural Correlates Constituting Novel Sounds to
Consciousness

• Jaaskelainen et al

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Jaaskelainen et al

• Purpose
• Find the neural mechanisms that underlie
  preattentive gating awareness of novel sounds

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Jaaskelainen et al

• Methods
• Use fMRI, EEG, and MEG to show brain activity
  when auditory stimulation occurs
• auditory stimuli
• Novel stimuli
• Give novel stimuli alone
• Standard stimuli
• Give standard stimuli alone
• Novel Standard stimuli
• Give novel stimuli after standard stimulus

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Jaaskelainen et al
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Jaaskelainen et al

• Conclusion
• Neurons in posterior auditory cortex are more
  broadly tuned on sound frequency then that of
  anterior auditory cortex
• Processing of low-novel sounds is significantly
  delayed in the anterior auditory cortex
• High-novel sounds are processed quickly and enter
  consciousness soon through stimulation of
  un-adapted feature-specific neurons within
  posterior auditory cortex

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Vogeley et al

• Neural Correlates of First Person Perspective as
  One Constituent of Human Self-Consciousness
• Purpose
• To find the neural mechanisms associated with
  perspective taking

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Vogeley

• Methods
• A virtual seen consisting of an avatar and red
  balls in a room was presented by different camera
  viewpoints
• View points were either 3PP vs 1PP or a ground
  view (gv) vs. an aerial view (av)
• Camera viewpoints presented to normal viewers in
  an fMRI experiment
• Task of subjects
• Count objects as seen either from avatars
  perspective (3pp) or from their own perspective
  (1pp)

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Vogeley et al
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Vogeley et al

• Results
• When taking a 3PP, there was increased activity
  in the precuneus, the frontal cortex bilaterally,
  the cerebellum bilaterally, the left temporal
  cortex, and the occipitoparietal cortex on the
  left side.
• When taking a 1PP, there was increased activity
  in the lateral superior temporal cortex
  bilaterally including the insula, mesial cortical
  areas (both frontal and parietal), left frontal
  coretex and the right postcentral gyrus

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Vogeley et al

• Conclusion
• Even though there are joint neural mechanisms,
  decision making 3PP and 1PP rely on differential
  neural processes.

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First Neurobiological Accounts of Visual
Consciousness

• View 1
• Visual consciousness is a localized event
• Zeki and ffytche showed that the difference in
  seeing or not seeing was dependent on the
  activity of a single visual area area V5
• View 2
• Visual consciousness is a network of
  inter-related activity
• Lumer et al showed that perceptual transitions
  between 2 constant stimuli correlated with
  activity in a fronto-parietal network of areas.

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Consciousness as a Network

• Neural Correlates of the Attentional Blink
• Feinstein et al
• Kranczioch et al

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Feinstein et al

• Purpose
• To understand the path from sensory processes to
  conscious perception

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Feinstein et al

• Methods
• RSVP of numbers and letters
• Embedded in RSVP are T1 and T2
• T1 ? either odd or even string of numbers (ex.
  11111 or 22222)
• T2 ? either a neutral or aversive word
• Subjects told to focus on RSVP and then state
  whether T1 was odd or even, and whether T2 was
  seen
• fMRIs were taken though out experiment

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Feinstein et al
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Feinstein et al

• Results
• (a) chart depicting the areas of the brain that
  showed greater activity when T2 was identified
• (b) is another representation of an increase in
  activity when T2 was detected
• (c) Shows how the anterior cingulate, frontopolar
  cortex, and the medial prefrontal cortex increase
  in activity and thus consciously perceived T2

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Feinstein et al

• Conclusions
• Activation of the anterior cingulate, medial
  prefrontal cortex, and frontopolar cortex is
  involved in the conscious perception of T2
• Results support theory that consciousness is a
  product of interactions between many parts of the
  brain

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Kranczioch et al

• Purpose
• Identify brain regions assumed to be involved in
  controlling the access of information to
  consciousness
• Relevant conclusions of previous studies
• Interference between target and mask is
  associated with increased activation of
  frontoparietal network
• Includes lateral frontal, anterior cingulate, and
  interparietal areas

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Kranczioch et al

• Methods
• A RVSP sequence of 20 capital black letters and 1
  capital green letter were shown with no
  inter-stimulus interval
• RSVPrapid serial visual presentation
• The capital green letter played the role of being
  a defined target that the subject should focus
  on. ?will be referred to as T1 (target 1)
• The letter X was then denoted as the second
  target ? T2
• In the experiment, subjects were required to
  indicate after seeing the RSVP sequence if
• T1 was a vowel
• T2 was present
• Responses given via a response pad

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Kranczioch et al

• Methods Side Note
• T1 and T2 target relations in previous studies
• In an RSVP sequence when T2 followed T1 between
  200-400ms later, the detection of T2 was
  significantly impaired ? attentional blink window
• Accuracy for T2 detection was highest when
  immediately following T1 or at least 500 ms after
  T1

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Kranczioch et al

• Methods continued
• fMRIs were retrieved while sequence evaluation
  was taking place

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Kranczioch et al

• Results
• 6 conditions were studied
• Lag refers to amount of time which T2 followed
  after T1
• T2 detected (lag 1? 100ms after T1)
• T2 detected (lag 2)
• T2 missed (lag 1)
• T2 missed (lag 2)
• T2 detected
• No T2

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Kranczioch et al

• Results
• (A) Regions of the brain that were active when T2
  was detected and when T2 was absent
• (B) Regions of the brain that were active when T2
  was detected and when T2 was missed

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Kranczioch et al
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Kranczioch et al

• Conclusion
• Findings support that T2 is not detected because
  it doesnt reach working memory
• Targets that do not reach awareness are processed
  beyond a first stage of perceptual identification
• Supported by findings of increased activity of
  inferior frontal, parietal, and frontal/anterior
  cingulate cortex in the T2 missed trials in
  comparison to the T2 absent trials

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Pins and ffytche

• Purpose
• To Identify whether neural correlates of visual
  consciousness are localized or distributed.
• To Identify where the neural correlates are
  located

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Pins and ffytche

• Basic Ideas to keep in mind
• Whether the stimulus is seen or not seen
  indicates a difference between visual input and
  visual perception.
• If stimulus is seen, then visual perception has
  taken place
• Perception for this experiment is defined as a
  conscious visual experience

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Pins and ffytche

• Methods
• Visual stimulus portrayed
• Visual stimulus is composed of a circular
  sinosoidal grating of 1 cycle/degree appearing
  on a grayscale background.
• Each stimulus trial is composed of 5 parts
• Pre-stimulus warning sound
• Pre-stimulus waiting period (random variations in
  length of period to ensure no pre-stimulus
  anticipatory response)
• Stimulus presentation
• Post-stimulus warning sound
• Post-stimulus waiting period
• Every time the stimulus was seen, the participant
  was to indicate so by pressing a button

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Pins and ffytche

• Methods continued
• For each trial a fMRI (functional magnetic
  resonance imaging) was simultaneously taken.
• 16 axial slides parallel to the plane passing
  through the anterior and posterior commissures
  were taken every 2 sec per trial
• For each trial a EP (evoked potential) was
  simultaneously recorded as well
• EP neurophysiological components evoked by the
  task

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Pins and ffytche

• Results of fMRI
• Activations
• Visual Areas
• Thalamus, striate cortex, fusiform gyrus, and
  medial occipital lobe
• Motor Related areas
• Left sensory motor cortex
• Right cerebellar hemisphere
• Supplementary motor cortex in both hemispheres
• Auditory system
• Superior temporal gyrus bilaterally in the insula

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Pins and ffytche

• Results of fMRI
• Suppression
• Supra-marginal gyrus (parietal)
• Posterior cingulate and parahippocampul gyrus
  (limbic)
• In an extended region passing from supperior
  frontal sulcus through the medial frontal gyrus
  to the anterior cingulate gyrus

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Pins and ffytche
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Pins and ffytch

• Results of EP recordings during task
• Early components
• High-contrast supra-threshold grating evoked a
  series of positive and negative waves over OL and
  PL
• Intermediate latency components
• Yes trials elicited a negative
• Maximal over left parietal
• Late components
• A negative slow wave was present for yes trials
  but not for no trials or catch trials.
• Maximal over left parietal lobe

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Pins and ffytch
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Pins and ffytche
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Pins and ffytche

• Conclusions
• Activity correlating with consciousness is
  distributed over time
• Suggest that there is a segregation in primary
  and secondary correlates
• OL activity after stimulus presentation is likely
  to be the primary correlate of consciousness
• PL, FL, motor and auditory regions are most
  likely the secondary correlates of consciousness