Does perception originate in nerve endings, or in the brain itself?
What's worse, the cause of the woman's itch was not any problem her skin; in fact, the nerves in the itchy spot were 96% dead, so they could not have possibly conveyed itch signals to her brain. Rather, a neurologist thought that "the itch system in M's brain had gone haywire, running on a loop all its own."
[This speculation challenges] what neuroscientists call 'the naïve view,' and it is the view that most people, in or out of medicine, still have. We're inclined to think that people normally perceive things in the world directly. We believe that the hardness of a rock, the coldness of an ice cube, the itchiness of a sweater are picked up by our nerve endings, transmitted through the spinal cord like a message through a wire, and decoded by the brain."
But a theory that's emerged lately considers that sensory perceptions originate in the brain itself, where it integrates, rather imperfectly, nerve signals coming from the outside world. So it is entirely possible for a brain to experience a fantom itch in a place where there's nothing to itch. It also explains the phenomenon of phantom limb. It also talks about fascinating therapies to treat pain and discomfort in phantom limbs by tricking brain into accepting contradicting information regarding the missing limb.
Things in themselves (the unknowability of)
All in all a fascinating article, but what's most amazing about it is that it takes evidence from sciences that deals with tangible things, such as biology and neuroscience, and uses it to support a realm of inquiry that's commonly thought of as metaphysical.
"In a 1710 "Treatise Concerning the Principles of Human Knowledge," the Irish philosopher George Berkeley objected to [the naive] view. We do not know the world of objects, he argued; we know only our mental ideas of objects. "Light and colours, heat and cold, extension and figures -- in a word, the things we see and feel -- what are they but so many sensations, notions, ideas?" Indeed, he concluded, the objects of the world are likely just inventions of the mind, put in there by God."
All this reminds me of Kant, with his impossibility of knowing "things in themselves". It makes me want to regret not giving "Critique of Pure Reason" proper attention when it was mandatory reading for a philosophy course I took in college. As dry as it was, I vaguely remember being intrigued by its notion that what we think are experiences of real objects are actually just our own mental structures. My thought was, "there's got to be an idea for a science fiction story somewhere in there". :-) But the idea was too abstract to even try to turn it into a story. Now, however, I have a feeling that neuroscience could provide scaffolding on which to build a story exploring the most abstract (if not to say metaphysical) aspects of our existence. That, to me, is fascinating.