Chapter 18: Damaged Brains

• Brain damage-caused deficits one important source of evidence about the neural correlates of consciousness and other "mental" phenomena.
• E.g., loss of impulse control and planning ability in patients with damages frontal & prefrontal lobes supports the hypothesis that that choice and volition are localized in these areas. (see chapter 9)
  
•  "What is it like?" questions (257) associated with various deficits
  
• "What is it like not to notice you don't notice half the world?"
• "What is it like to be blind but believe that you can see, or paralyzed but convinced that you can move?"
• "What is it like to be suspended in the present moment with no memory."
  

Amnesia

• Two types
• retrograde: loss of long term memory that stretches back into the past
• anterograde: loss of the ability to store new long-term memories
• Korakoff's syndrome & Jimmie G.
  
• an anterograde amnesia caused by alcoholism (generally)
  
• accompanied by retrograde amnesia (naturally) dating back to the onset of the syndrome (& before?)
• Oliver Sacks described J.G.'s amnesia as "a bottomless memory-hole that would engulf the whole world." (1985: 34)
• "episodic memory (that is memory for the events of one's life) remains perfectly good for the far past, before the blank period, but no new episodic memories are laid down. (258)
• many remaining memory-like abilities (258-9)
• to be classically conditioned: e.g., to blink at a sound which has been associate in past trials with a blast of air to the eye
• "to associate smells with lunchtime"
• "to respond to a given visitor with pleasure, even if they claim never to have seen that person before"
  
• skills
• retain such skills as driving & typing
• can even acquire new skills unawares, as it were -- like. learning to play the piano without "remembering" ever having a lesson
  
• SB's analysis (259-60)
  
• surely, amnesiacs are conscious: "They are awake, responsive, able to converse, laugh and show emotion."
• "But who is conscious?"  That's the question.
• "Without the capacity to lay down new memories, their self is a person trapped in the past, unrelated to the events and people of the present."
• "They have lost the interaction between current and stored information that, according to Weiskrantz (1997), makes possible the "commentary" that underwrites conscious experience."
• "Some amnesiacs repeatedly exclaim, 'I have just woken up!' or 'I have just become conscious for the first time!'"
  
• Sacks: "If a man has lost a leg or an eye, he knows he has lost a leg or an eye; but if he has lost a self -- himself -- he cannot know it, because he is no longer there to know it." (1985: 34)
• Still, "a man does not consist of memory alone.  He has feeling, will, sensibilities, and moral being."
  

Neglect

• Anosagnosia: Paralysis neglect,
•  e.g., "a patient who is paralyzed down his left side may say that he can move perfectly well if he wants to"
• caused by certain kinds of right-brain damage
  
• Anton's syndrome: blindness neglect
• "Patients are blind and yet insist that they can see."
• "When they bump into things, as they frequently must, they confabulate, inventing an ingenious range of excuses rather than concluding that they are blind." (260)
• Hemifield or unilateral neglect:
  
• the syndrome
• caused by right-brain damage
  
• "patients seem not to realize that the-hand side of the world even exists"
• e.g., clock faces drawn by hemifield neglect patients (Fig. 18.1: 261): http://www.medicine.mcgill.ca/Strokengine/images/bmjfigurebigger.jpg
• puzzlingly seems also to affect remembered scenes as well as visually present scenes
• characterizations & explanations (262-3)
  
• "Hemifield neglect can partly be explained as a deficit of attention, in that patients simply do not attend to, or have their attention drawn to, the left-hand side of the world"
  
• "clearly the unattended side is not completely blanked out"
• "emotional stimuli shown in the neglected field can influence attention and stimuli that are not consciously seen can prime later responses."
  
• "In one experiment patients were shown two pictures of a house, identical except that one had flames pouring from a window on the left-hand side.  While insisting that the houses were identical, patients still said that they would prefer to live in the [the bottom house in this instance (Fig. 18.2), i.e., the] one that is not on fire."
  

Blindsight

• Patient D.B. (263)
  
• had part V1 of his left visual brain removed, leaving him blind on the right side "since input from the right visual field goes to the left brain, and vice versa"
  
• "If he looks straight ahead and an object is placed on his blind side, he cannot see it" -- or so he says
• Weiskrantz's blindsight experiment (see Fig. 18.3)
  
• show a circle with stripes in his normal field he says he can see it and easily tells whether the stripes are vertical or horizontal
• shown the same circles in his "blind" field he denies he sees anything yet his forced "guesses" are 90-95% correct.
• Related phenomena that have been observed
  
• "deaf hearing"
• "blindsmell"
• "numbsense" (Weiskrantz 1997)
• Interpretations, etc.
  
• The obvious  interpretation: "the blindseer has vision without consciousness" (265)
• showing "that consciousness is something separate from the ordinary processes of vision"
• "that qualia exist and functionalism is wrong"
• that there is a "finishing line" and a "Cartesian theater" after all
  
• the "stray light" hypothesis disconfirmed
• Presumptive physiological basis: "There are something like 10 separate, parallel pathways from the eye to different parts of the brain.  About 85 percent of cells take the major route through the lateral geniculate to primary visual cortex, gut the rest go via the superior callicus to various other cortical and subcortical areas.  ...  The evidence suggests that true blindsight occurs when V1 is destroyed and these other pathways remain intact."
• Weiskrantz: "The subjects seemed to be able to respond to the stimuli that would normally generate the philosophers' favourite species of 'qualia,' namely colours, but in the absence of the very qualia themselves!" (1997: 23)
• Dennett's Challenge: superblindsight
• blindsight subjects "have to be prompted to guess and are given no immediate feedback on their success" (266)
• suppose instead we train the subject "giving him feedback on his guesses until he comes to realize that he has a useful ability.  Next he is trained, again by giving feedback, to guess on his own, without being prompted.  After this training he should spontaneously be able to talk about, act upon and use the information from his blind field just as well as from his seeing field." (266)
• at issue: "if the superblindseer could really use the information about a stimulus in the blind field in this way, would that mean he was necessarily conscious of it?"
  
• Cognitivism (e.g., Dennett) say "yes":
  
• functional equivalence => phenomenal (i.e., conscious or experiential) equivalence
• full-functional zombies are impossible
• anticognitivists say "no"
  
• functional equivalence =/> phenomenal equivalence
• full-functional zombies are possible
  
• pertinent fact: actual blindsight is not fully functional
  
• "blindseers generally cannot recognize forms or identify familiar objects"
  
• "They cannot (or at least do not) use their blindsight in ordinary life."
• some blindseers are aware of fast-moving, high-contrast phenomena in their blind field, in effect, "seeing movement without seeing the thing that is moving" or "not bound to a moving object" (268)
• "the intact field seems biased towards object identification, and the Blindsight field towards stimulus detection" (269)
• sensory substitution: using one sensory modality (e.g., touch or hearing) to process information from another (e.g., vision): "with practice it seems [to them] to become more and more like seeing" suggesting "consciousness comes along with increasing function rather than being something separate from it" (269)
• Block's analysis (1995)
• distinguish between access consciousness (Consciousness) and phenomenal consciousness (Consciousness) (SB: 269)
  
• A = "the availability of information for use in reasoning, speech and action"
• P = "experience or 'what it is like' to be in a given state"
  
• Block argues that stimuli in blindsight are unconscious in both ways
• "For Block the superblindsight case is indeed a partial zombie who has A-consciousness (because he can talk about stimuli in his blind field) but no P-consciousness (because he has no visual qualia).
• Dennett disagrees: "blindsight does not support the concept of a zombie, it undermines it" (270)
• Weiskrantz's view (tending to support Dennett)
• W's hypothesis: blindseers lack the "commentary stage":  a kind of HOT theory
  
• this is exactly what's added in Dennett's superblindseers
• Dennett's superblindseers would be expected to regain consciousness upon having their "commentary stage" thus restored, then, on W's hypothesis.