As a general rule, this is an accurate representation of our bodies: everything is in normal proportions to how we see ourselves. Ask yourself this question, when you hold something in your hand, do you think it feels the same if you now put is on your back or against your cheek or on your foot? After all it is the same skin. But it is registering the same in the brain?

images-3First, we need to do a test. You will need 2 things:

1) a friend or family member to help you and 2) two pointy objects, like two pencils or two pens.

Starting with one of your palms, have your friend touch your palm with both pens at the same time a couple of inches apart. You will be able to feel the two points. (Note: you must not look when doing this. Turn your head away from the pens.) Now move the pens closer together and do it again. Did you feel two points again? Keep going until you no longer feel two separate points, but they have merged into one point. Mark how far apart the pens are.

Now do this same experiment on your back. How far apart were the pens when you felt both pens as one? Now try it on your thumb. Close your eyes and try it on your cheek.

Were all of the distances the same on the different parts of your body? They shouldn’t be! Here is what we look like from our brain’s point of view:

homunculus1

See how large our heads, hands, and feet are? That is because there is more sensory cortex devoted to these areas. This helps you make finer movements and have a better sense of touch. So the distances on your hands, thumb, and cheeks should be smaller compared to your back or your legs because they are more sensitive. Your back and legs cannot discriminate touch as much as these other parts of your body.

 

This above person is called a Homunculus. It is an interesting word. It means “little man”.  A Canadian doctor by the name of Wilder Penfield while studying patients with epilepsy created maps of the brain. Here is his interpretation of how our sensory cortex sees our bodies:

You can have your very own 3D model of a sensory homunculus. I found one on etsy. Here is the link http://www.etsy.com/listing/70834583/sensory-homunculus-model-made-to-order.