Sunday, January 11, 2009

101 Interesting Things, part 2: Pain Asymbolia

Pain asymbolia is a neurological condition resulting from brain damage that causes the victim to lose the affective quality of pain while still experiencing the stimulus as pain.  In other words, the qualia of pain is lost.  This condition can be brought about intentionally by performing an operation upon the insula, a treatment sometimes used for patients with chronic pain.

Sense perception and qualia can be very strange to our common-sense notions at times.  Much is made of the "redness of red" when speaking of qualia, but a better example is available:  that of taste.  It can be conceptually difficult for one to distinguish the ideas of a perception of wavelength x of light and the qualia of redness, even though one may be well-versed in the operations of the eye's rods and cones and the brain's optical processing mechanisms.  Taste is a better example because the taste buds react based on the shape of a molecule and the mind produces the qualia of sweet, or sour, or whatever.  But pain asymbolia forces a further distinction:  not only that a painful stimulus creates a sensation in the mind, but also that the sensory experience is itself distinct from the qualia of pain.

Adam "Ebonmuse" Lee (of Ebon Musings and Daylight Atheism fame) writes, in "A Ghost in the Machine," pain asymbolia is distinct from pain insensitivity and other related disorders, in that:
"Patients with this condition lose no sensory perception - they can tell the difference between heat, cold, touch, and various other sensations - but what they seem to lose is the emotional response to pain (Feinberg 2001, p. 4). ... After the operation, they are invariably much more cheerful, and say things such as, 'The pain is the same, but I feel much better now' (Damasio 1994, p. 266). What have these people lost if not their 'pain' qualia?"
From the Stanford Encyclopedia of Philosophy's entry on pain, one of the common ideas about pain is that "pain experiences are essentially painful, awful, abhorrent, so that it is a logical impossibility to have an affectively neutral pain experience."  Pain asymbolia would seem to directly undercut that, in line though it is with our common-sense notions of what pain is like.  It could be that the "awful" component of pain is a purely emotional response tied to a particular set of stimuli, and this is corroborated by the fact that the role of the insula is related to emotions.  However, it seems a bit strange on first blush to suggest that the "painful" aspect of pain is not a direct result of the damage caused by the physical stimulus (patients with pain asymbolia show no difficulty in sensing this part, as it is handled by the somatic sensory cortex), but an entirely emotional response generated by a different part of the brain.

Furthermore, the SEP article also points out that the dissociation caused by pain asymbolia is distinct even from similar dissociations that can arise in lobotomy patients or people on morphine.  These latter groups still respond to momentary pains (e.g. small cuts or pinpricks), but those with pain asymbolia do not.  It appears that just as involuntary reflexes (originating from the spine) are reactions to stimuli that do not involve any conscious processing at all, so too is the qualia of pain a separate process, even though common experience would suggest the opposite.  How interesting!

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