eli5 How does localisation of sensation work? Do the nerves have to be in the right spatial location or is it more an illusion?
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The nerves that link a finger to the brain is a bit like a wire it literally carries the signal from one end to the other. The brain knows which nerves travel to which location so knows that an electrical signal in that nerve means a particular place on the body is sensing something. There is a thing called dermatomes which form the end points of the nerves at the skin that does the sensing and the pathways of those nerves to the brain is known and forms a map of the skin.
The nerve that goes to your leg for example enters/exits the spinal column in a particular place before carrying the signal to the brain. If there is a problem at that spinal joint you can get what’s known as referred pain, where the brain thinks the leg hurts when the nerve is actually being pinched in the spine.
So sensing is very much geared to the entry point to the brain, when the electrical signals reach the brain does it’s best to guess what’s going on by which nerves are being are carrying a signal, the brain is good a guessing but can get it wrong.
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