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.
The Homunculus Mapper and its associated images and text are covered by a Creative Commons license (CC BY-NC-SA).
The Homunculus Mapper web site was created by members of Dr. David Fitzpatrick’s laboratory at the Max Planck Florida Institute for Neuroscience. The site describes the classic two-point discrimination experiment, but gives it twist by allowing people to visually display their results graphically.
First, follow the step-by-step instructions to map the sensitivity of different parts of your body.
1. You will create cards with toothpicks separated by different distances that will allow you to test whether one or two points are detected.
http://www.maxplanckflorida.org/fitzpatricklab/homunculus/experiment/
2. Keep track of the distances when someone says that they only feel one point even though two toothpick points touched their skin.
ww.maxplanckflorida.org/fitzpatricklab/homunculus/experiment/
After you have collected your data, go back to the main page and select a model.
Enter your data for the different parts of the body to see how the sensitivity of different parts of your body is mapped to your brain.
http://www.maxplanckflorida.org/fitzpatricklab/homunculus/experiment/
You can even print out your final “homunculus.”
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