Consciousness and the Brain

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Consciousness and the Brain

• Jeff

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Consciousness

• The mind-brain problem
• What is the nature of mental states and
  processes?
• What medium do they take place in?
• How are they related to the physical world?
• Does consciousness survive death?
• Can a purely physical system construct conscious
  intelligence?

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Dualism

• The mind and brain are two distinct entities and
  that conscious experience is nonphysical and
  beyond the scope of the physical sciences
• Popular dualism
• Property dualism
• Interactionist property dualism

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Popular Dualism

• People are ghosts in the machine
• Spatial properties of the ghost interact with
  spatial properties of the machine
• Matter is merely a manifestation of energy
• Nonmaterial thinking substance

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Property dualism

• No substance beyond the physical brain
• Brain has unique nonphysical properties unlike
  other physical object

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Interactionist property dualism

• Similar to property dualism
• Holds that mental phenomena can affect the brain,
  and via that behavior
• Believes that mental properties are emergent and
  irreducible

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Materialism

• The brain enables the mind and that different
  parts of the brain play specific roles in our
  mental life
• Philosophical behaviorism
• Reductive materialism
• Functionalism

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Philosophical behaviorism

• Can not talk about inner experience at all
• Only peoples capabilities and dispositions are
  discussed because they are measurable

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Reductive materialism

• Mental states are physical states of the brain
• Each mental state or process is numerically
  identical with some physical state or process in
  the brain

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Functionalism

• One mental state makes ineliminable reference to
  other mental states
• Because of this behaviorism is not sufficient
• Anything that appears to be aware in the same
  way as a human is functionally equivalent, and in
  many respects should be treated as equivalent

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Dualism vs Materialism

• Dualism
• Biggest critique Doesnt allow for much
  investigation
• Materialsim
• Biggest critique Doesnt take subjective
  experience into account very much (i.e. qualia)

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3 Issues of Consciousness

• Pinker, 1997
• Sentience - subjective experience, phenomenal
  awareness, raw feelings, first-person tensewhat
  it is like to be or do something
• Access to information - the ability to report on
  the content of mental experience without the
  capacity to report on how the content was built
  up
• Self-knowledge - having accurate information
  about oneself

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Related Cog Neuro Work

• Split brain
• Word pair free association
• Unconscious processing
• Subthreshold presentation w/ lexical decision
• Blindsight
• Hemineglect

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Word Pair Free Association

• Nisbett et al. (1980)
• Participants learned word pairs (e.g. ocean-moon)
• Participants then later asked to free associate
  other words
• For this example, participants given ocean-moon
  would associate tide with the word detergent

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Unconscious Processing

• Stimuli presented subthreshold stimuli
• i.e. stimulus is presented so fast participant
  has no conscious awareness of it
• Participants then shown a second stimulus and
  asked to perform tasks based on it
• Unconsciously perceived stimuli affect responses

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Lexical Decision

• Marcel (1983)
• Type of unconscious processing study using a
  lexical decision task
• Participants either performed lexical detection
  or decision task
• Subthreshold words affected reaction time for
  subsequent stimuli if they were related
• e.g. bread/sandwich vs truck/sandwich

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Split Brain Patients

• Left hemisphere interpreter
• Patients have no conscious access to cause of
  actions controlled by the right hemisphere
• Picture matching task
• Tachioscopic word presentation to the left visual
  field

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Blindsight

• Patients with a lesion in visual cortex can
  respond to stimuli in their blind field
• They are not conscious of their perception
• Use a Purkinje eye tracker with an image
  stabilizer to present images
• Participants make judgements about stimuli and
  perform above chance in their blind visual field
• Perception happens without sensation?

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Hemineglect

• Patients do not have conscious access to half of
  their visual field (visual cortex is intact,
  usually a parietal lesion)
• Can still make same/different judgements above
  chance
• Can still show priming effects for stimuli in the
  neglected hemifield

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Questions Revisited

• What is the nature of mental states and
  processes?
• What medium do they take place in?
• How are they related to the physical world?
• Does consciousness survive death?
• Can a purely physical system construct conscious
  intelligence?

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The End