//notes from The Itch by Atul Gawande, (Its mysterious power may be a clue to a new theory about brains and bodies.)

[source: http://www.newyorker.com/reporting/2008/06/30/080630fa_fact_gawande?currentPage=all]

_“the naïve view,”

_direct-perception theorypeople normally perceive things in the world directly.
_For one thing, it cannot explain how we experience things that seem physically real but aren’t: sensations of itching that arise from nothing more than itchy thoughts; dreams that can seem indistinguishable from reality; phantom sensations that amputees have in their missing limbs. And, the more we examine the actual nerve transmissions we receive from the world outside, the more inadequate they seem.

_Our assumption had been that the sensory data we receive from our eyes, ears, nose, fingers, and so on contain all the information that we need for perception,

_So you might think that it’s the same with the signals we receive—that if you hooked up someone’s nerves to a monitor you could watch what the person is experiencing as if it were a television show.

_If visual sensations were primarily received rather than constructed by the brain, you’d expect that most of the fibres going to the brain’s primary visual cortex would come from the retina. Instead, scientists have found that only twenty per cent do; eighty per cent come downward from regions of the brain governing functions like memory.

_They put their surviving arm through a hole in the side of a box with a mirror inside, so that, peering through the open top, they would see their arm and its mirror image, as if they had two arms. Ramachandran then asked them to move both their intact arm and, in their mind, their phantom arm—to pretend that they were conducting an orchestra, say. The patients had the sense that they had two arms again. Even though they knew it was an illusion, it provided immediate relief. People who for years had been unable to unclench their phantom fist suddenly felt their hand open; phantom arms in painfully contorted positions could relax. With daily use of the mirror box over weeks, patients sensed their phantom limbs actually shrink into their stumps and, in several instances, completely vanish.

_an experiment in which he put ice-cold water in people’s ears. This confuses the brain’s position sensors, tricking subjects into thinking that their heads are moving, and in certain phantom-limb and stroke patients the illusion corrected their misperceptions, at least temporarily.

_If you take two mirrors and put them at right angles to each other, you will get a non-reversed mirror image. Looking in, the right half of your face appears on the left and the left half appears on the right. But unless you move, he said, your brain may not realize that the image is flipped.

_“Now, suppose she looks in this mirror and scratches the left side of her head. No, wait—I’m thinking out loud here—suppose she looks and you have someone else touch the left side of her head. It’ll look—maybe it’ll feel—like you’re touching the right side of her head.” He let out an impish giggle. “Maybe this would make her itchy right scalp feel more normal.” Maybe it would encourage her brain to make a different perceptual inference