Meet your homunculus

What can you say about your brain? You would probably describe it as a main organ of the nervous system,  a control centre for all mental processes, a 3lb  mass of grey and white matter with wrinkled surface etc...

 

Now imagine for a moment that you asked your brain to do just opposite - to describe YOU. If you are hoping to hear something like "A sexy brown-eyed male with a great karaoke talent", think again. In your brain's view, you are quite an ugly creature with oversized tongue and lips and massive dangling hands. Meet your HOMUNCULUS.

Homunculus ("little man" in Latin) is, of course, not a creature living inside your head, but a way your body is "mapped" onto the surface of your brain. Huge tongue and small feet simply means that more of the cortical tissue is allocated to "service" your tongue than feet.

Two in one

In reality, there are two homunculi - a sensory one and a motor one (see the pic below). Corresponding brain areas are called somato-sensory cortex (in blue, this part receives sensations from your body parts) and motor cortex (in red, this part sends out movement commands to the body parts).

Many body areas are mapped to a similar scale in both cortices. For instance, both cortices have large representation of hands. This is, of course, because skin of our hands, in particular palms and fingers, has high density of touch receptors, and, at the same time, hands have large number of skeletal muscles, controlled by the motor cortex, enabling us to execute very fine movements like playing piano.

In other ways, the body maps differ. Motor homunculus, for example, is missing several areas, like intestines, back of the head or genitals. The reason for this being, although you can feel the pain in your intestines or pleasurable touch to your genitals, you cannot consciously command to these parts to move (imagine how much more entertaining your life would be if you could)...

 Never alone

So here is a comforting thought. Whenever you feel lonely - think of your homunculus who is always around, feeling what you are feeling and doing what you are doing, but who is nowhere near as good looking as you are!

Thanks for reading!