Chapter 16: The Neural Correlates of Consciousness

• Blackmore's Question: "If you could look right inside the brain and see everything that was happening there, would you then understand consciousness?"
• Yes: Identity theorists, eliminativists(?)
• No: Mysterions, dualists, behaviorists
• Depends what you mean by "see everything": functionalists
• The mystery: "[H]ow can this physical lump of stuff, with its chemical and electrical activity, be the seat of consciousness?" (226-7)
• Search for the neural correlates of consciousness (NCCs) -- screw the mystery
  
• Correlation 101: if A and B are correlated -- "constantly conjoined" (Hume) -- there are five possibilities
1. A causes B
2. B causes A
3. C causes both B and A
4. A = B
   
5. chance or accident ("there's no explanation")
   

Unconsciousness

• Hope: to determine the NCC by discovering what's different about the brain when it's unconscious.
• Sleep: "is in fact a rather complex mixture of different states" (228)
• Coma & persistent vegetative states: "it was shown during the nineteenth century that animals with the whole cortex removed can still show an alternation of sleeping and waking states" (229)
  
• Anesthesia: "Anesthetics are mostly rather non-specific in their effects, and ... their mechanisms of action are not well understood."
• "countless chemicals ... induce unconsciousness, but they do so in different ways" (231) it seems

Conscious Vision

• Crick's quest for "the 'neural correlate of visual awareness" (1994: 204), for the correlates of the "vivid representation in our brains of the scene immediately before us" (231).
• Localization issues
• James' deriding of the quest for some "pontifical neuron" to which "our consciousness is attached"
  
• :"The consciousness, which is itself and integral thing not made of parts, 'corresponds' to the entire activity of the brain, whatever that may be, at the moment."
  
• "The ultimate of ultimate problems ... is to understand how such disparate things are connected at all." (James, 1890, Vol. 1: 177)
  

Competing for Consciousness

• Rivalry phenomena
• the Necker cube (Fig. 16.2: 233 | online animation) "can be seen in two mutually incompatible ways ... so you experience alternation or rivalry" (233)
• binocular rivalry: when different images are presented to the two eyes
• they don't fuse
• they alternate or compete
• Experiments to differentiate "those brain processes that are qualia laden as opposed to those that are not" (Ramachandran & Hubbard, 2001: 24)
  
• Macaque monkeys: inferior temporal cortex (IT) seemed to correlate with the alternations
• Related human studies "add to a body of work suggesting that conscious visual experiences are correlated not with the activity of V1 and other early parts of the sensory pathways but with more central areas. (235)
• Crick & Koch's conclusion: "It is the transient results of the computations which correlate with qualia; most of the computations leading up to those results are likely to be unconscious" (2000: 104)
• Skeptical doubt: if "there is no 'vivid representation in our brains of the scene directly before us' and no 'movie-in the brain'" then "looking for their neural correlates is doomed to failure" (236)
  

Pain

• The hard question: regarding the subjectivity of pain
• International Association for the Study of Pain's definition: "an unpleasant sensory and emotional experience associated with actual or potential damage"
• adding, "Pain is always subjective."
• Typical hard problem dilemma: concerning those with a "high threshold of pain" [like the taste of asparagus example]
  
• are the pains of those with a "high threshold of pain" less qualitatively intense?
  
• or are they just more stoic: given the same qualitative intensity, they just mind it less
• The where? question
• pinch your arm
• where was the pain?
• in your arm (the naive or common-sense view)
• in your brain (the identity theoretic view)
• in consciousness (dualism)  -- n.b. consciousness is no place
• phantom limb experiences challenge the naive view (238)
  
• amputees may feel pain "in their leg"
• when they have no leg
• the somatosensory homunculus (fig. 16.5)
  

Whose Pain?

• Amazing fact: among some humans and "animals whose spinal cords have been severed ... if a stimulus that would ordinarily be painful is applied to the leg ... [the individual] shows no signs of distress, but its leg automatically withdraws.  ... "The isolated spinal cord can even be taught to make responses by training it with stimuli that would be painful for the whole person but are not felt at all by the paralyzed person." (238)
• Animal pain denial: HO theories
  
• Descartes ... animals have the "corporeal image" without the conscious experience
• the conscious experience (quale?) = the soul's perception of the corporeal image
• animals don't have souls
• Similarly, Demasio: "the neural signals that correspond to the substrate of pain ... are displayed in the appropriate areas of the brain stem, thalamus, and cerebral cortex and generate an image of pain, a feeling of pain" (1999)