If you’ve ever had the misfortune of seeing this creature, called a sensory homunculus, you’ve probably wondered what it is. In short, this model is a visual representation of the way the human brain perceives the sensory information it receives from the body.
The body is equipped with receptors that sense touch, feeling, temperature, and pain; and they relay information about that touch through the nerves and into the brain. This information is sent by electrical and chemical “messengers” to an area of the brain called the somatosensory cortex. This area is responsible for interpreting and understanding these senses and the information it relays (for example, you can tell by touch whether a surface is rough or smooth).
The cortex is fairly large, but it still has a limited amount of space and therefore only has so many signals it can process at a time. This is why it has to consider where it would be most useful to focus more of its processing power. There are areas of the body where it doesn’t need to pay as much attention to the fine detail of what it senses from outside – for example, the leg or chest – since they don’t usually receive too much information at a time. There are other places, however, that receive much more information and require a lot more effort to understand.
For example, we explore a lot of the world using our hands. We pick things up with them and use them to feel objects or environments around us, meaning they’re constantly picking up a lot of sensory information. This is why it’s useful for the brain to spend a lot of processing power on interpreting the many signals coming from the hands. The lips and tongue are also very important to understand, because they come into contact with everything we eat. They receive detailed sensory information very often, so much like the hands, the brain devotes a lot of sensory “real estate” to interpreting the information they collect.
All this means that the sensory centers in your brain aren’t evenly divided, with much more space dedicated to analyzing the most “important” areas. This is, finally, where the sensory homunculus (literally meaning little man) comes in – the more space and sensory processing power the brain devotes to a certain area, the more exaggerated the area is on the homunculus. This results in a somewhat cartoonish figure with a gigantic head, mouth, and hands; much like the one you see above. In a sense, it represents how this part of the brain sees your body when it processes everything you touch.
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