Mouseunculus: How The Brain Draws A Little You

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Inside each of us is a miniature version of ourselves. The Canadian neurologist Wilder Penfield discovered this little person in the 1930s, when he opened up the skulls of his patients to perform brain surgery. He would sometimes apply a little electric jolt to different spots on the surface of the brain and ask his patients–still conscious–to tell him if they felt anything. Sometimes their tongues tingled. Other times their hand twitched. Penfield drew a map of these responses. He ended up with a surreal portrait of the human body stretched out across the surface of the brain. In a 1950 book, he offered a map of this so-called homunculus.


For brain surgeons, Penfield’s map was a practical boon, helping them plan out their surgeries. But for scientists interested in more basic questions about the brain, it was downright fascinating. It revealed that the brain organized the sensory information coming from the skin into a body-like form.

There were differences between the homunculus and the human body, of course. It was as if the face had been removed from the head and moved just out of reach. The area that each body part took up in the brain wasn’t proportional to its actual size. The lips and index finger were gigantic, for instance, while the forearm took up less space than the tongue.

That difference in our brains is reflected in our nerve endings. Our fingertips are far more sensitive than our backs. That’s because we  don’t need to make fine discriminations with our backs, while we use our hands for all sorts of things–like picking up objects or using tools–that demand sensory power.

The shape of our sensory map reflects our evolution, as bipedal tool-users. When scientists have turned to other species, they’ve found homunculi of different shapes, the results of their different evolutionary paths.

Written By: Carl Zimmer
continue to source article at phenomena.nationalgeographic.com

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    • In reply to #1 by Sjoerd Westenborg:

      Absolutely fascinating.

      Yes, that is my exact thought as well.

      I find it interesting that the ratio of the human head to the body is about 1:7 ish. It looked like 1:2.5 in the diagram. Not surprising we spend much time focusing on our faces. Hey Stafford, Genitals are at the end of the road in the diagram. I’m not sure exactly how much space is “allotted.” Being next to toes, I wonder if it explains why some people have foot fetishes.

      • In reply to #3 by QuestioningKat:

        In reply to #1 by Sjoerd Westenborg:

        One thing that surprised me was the small area allocated to teeth and jaw. They are the best areas for generating pain.

        When I first studied the diagram, I was very into massage. I was surprised that the map had nothing to do with how pleasurable an area was to massage. I speculate the back is so pleasurable because it is hard to massage yourself. You require a partner.

        The oddest thing is the way the genitals are not in place but off the end (perhaps to allow room for growth).

  1. It all makes sense but, I have to say that I’m somewhat disappointed with proportion of the area relating to the genitals; for my part, I only have think about that particular region of my anatomy for it to increase in size.

    • In reply to #2 by Stafford Gordon:

      It all makes sense but, I have to say that I’m somewhat disappointed with proportion of the area relating to the genitals; for my part, I only have think about that particular region of my anatomy for it to increase in size.

      Just wait until you’re an old fart like me. You brain will actually plot against you. Sorry, not something to look forward to. You guys gave me a good laugh this morning, thanks!!

  2. That’s amazing! I just watched a documentary on this very subject last night. It was a National Geographic show called ‘Blow Your Mind’. It shows how your brain can and will lie to you under certain conditions (placebo, sensory, ect.) You should check it out if this stuff interests you. I thought it was incredibly interesting.

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