The brain processes pain. Its tissue lacks the sensors.

Here's the strange part.

The organ that interprets pain does not have pain receptors in its own tissue. That distinction helps make awake brain surgery possible. It does not mean headaches are imaginary: the meninges and other structures around the brain have pain-sensitive nerves. The brain is central to the experience of pain without its tissue needing the same sensors. (BrainFacts / Society for Neuroscience)

Go straight to the receipts.

Curious about the methods, dates or details? Open the original source and keep the caveat in view.