Applied Philosophy: Representation, Metarepresentations, and Qualia
V.S. Ramachandran (2004), A Brief Tour of Human Consciousness (New York: Pi Press: 0131872788):
p. 108 ff: In chapter 2 I mentioned the "blindsight" syndrome, in which a patient with visual cortex damage cannot consciously see a spot of light shown to him, but is able to use an alternative spared brain pathway to guide his hand unerringly to reach out and touch the spot. I would argue that this patient has a representation of the light spot in his spared pathway, but without his visual cortex he has no representation of the representation--and hence no qualia "to speak of."
Conversely, in bizarre syndrome called Anton's syndrome, a patient is blind owing to cortical damage but denies that he is blind. What he has, perhaps, is a spurious metarepresentation but no primary representation. Such curious uncoupling or dissociations between sensation and conscious awareness of sensations are only possible because representations and metarepreentations occupy different brain loci an can therefore be damaged (or survive) independently of each other, at least in humans....
The flip side of this is, just as we have metarepresentations of sensory representations and percepts, we also have metarepresentations of motor skills and commands such as "waving goodbye," "hammering a nail in the wall" or "combing," which are mainly mediated by the supramarginal gyrus of the left hemisphere.... Damage to this structure causes a disorder called ideomotor apraxia.... [I]f asked to "pretend" to hammer a nail into a table, they will make a fist and flail at the tabletop.... Or when asked to mime combing her hair a patient will make a fist and bang it on her head, even though she understands the instruction and is perfectly intelligent in other respects. The left supramarginal gyrus is required for conjuring up an internal image--an explicit metarepresentation--of the intention and the complex motor-visual-proprioceptive "loop" required to carr it out. That the representation of the movement itself is not in the supramarginal gyrus is shown by the fact that if you give the patient a hammer and a nail he will often execute the task effortlesly...
p. 147 ff: The second problem is why the sensations take the particular form that they do.... [Q]ualia--consider the manner in which we experience... wavelength... and pitch.... Even though wavelength is a continuous dimension we experience colors as four qualitatively distinct sensations--red, yellow, green, and blue.... Adjacent colors... are "miscible"... we can see orange as a blend of red and yellow and purple as comprising red and blue. But non-adjacent ones are immiscible... it is hard to even imagine a bluish yellow or a reddish green. Thus color sensations seem chopped up into four immiscible bits. But this isn't true of soundwaves... we hear the full range... as a continuum, with no breaks in qualia. All this is obvious, but the question is why....
The fact that different modes of experience apply to wavelength and pitch suggest that qualia cannot be epiphenomenal; they must have an evolutionary function--such as serving as a mnemonic aid....
Non-spectral colors are perhaps the strangest thing of all. There is no wavelength that is purple--purple is a mixture of short (blue) and long (red) wavelengths. As you go around the color wheel starting at red, you can shorten and shorten the wavelength and go smoothly through orange and yellow and green to blue and then, as you continue around the color wheel, you have to add long (red) wavelengths while keeping the blue wavelengths to get purple, and then take away the short (blue) wavelengths to get red. And there is nothing in your consciousness or its qualia to tell you what your retina knows very well: that going from red to blue through orange, yellow, and green is a very different process on the photon level than going from blue to red through purple. Not only do we have qualia, but they are very false to the way the universe really is. Purple is not a wavelength halfway between red and blue. Green is a wavelength halfway between blue and yellow.
