There is a map of your body surface on your brain’s cortex. But the map isn’t proportional to actual space.
Sensitive parts like your face and hands use more space than less sensitive parts like your legs or back.
You can test the sensitivity of the body parts using two-point discrimination. When two nearby points touch your skin it can feel like just one object. The more sensitive the body part is the easier it is to feel both points. By testing what you feel on different body parts you can make a cortical representation of the body, called a cortical homunculus. In a cortical homunculus, more sensitive body parts are larger and less sensitive body parts are smaller.
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