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From The Undefeated Mind: On the Science of Constructing an Indestructible Self by Alex Lickerman MD
“Pain is a fascinating phenomenon. The way the brain registers physical pain, for instance, is not only complex but counterintuitive.
Though the pain of a stubbed toe or a headache may seem like a single, unified experience, it actually represents the sum of two different experiences created by two separate areas of the brain—one called the posterior insula, which registers the sensation of pain (its quality, intensity, and so on) and the other the anterior cingulate cortex, which registers pain’s unpleasant character.
We know this is how the brain experiences pain because of imaging studies and because patients who’ve had damage to the anterior cingulate cortex feel the sensation of pain but not its unpleasantness.
That is, they feel pain but aren’t bothered by it (interestingly, in some people, morphine has the same effect).
When the anterior cingulate cortex isn’t functioning, pain is still experienced but seems to lose its emotional impact and thus its motivating force.
This finding, that the sensation of pain and the unpleasantness of pain come from distinct neurological processes that occur in different locations within the brain, explains how a single pain stimulus can cause such subjectively different pain experiences.
Even if the physical sensation of pain remains constant, our “affective reaction” to it—how much it makes us suffer—will vary tremendously depending on several factors.”
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