In this chapter of the Neuroscience of Autism Spectrum Disorder series, I want to talk about changes in a brain region called the insula cortex. And just like that we have moved to our first structure in the cortex. The cortex is the thin layer on the outer surface of the brain. And even though the cortex is only about an inch thick, it is mostly this region that sets humans apart from other animals. The cortex is what allows for really complex intelligence, and not surprisingly its functions are very complex and mysterious. In humans, the cortex has grown so large that it won’t even fit on the top of our brains anymore, so instead it is wrinkled up. That’s why when you see a picture of a human brain you see a wrinkly mess. The bigger the cortex, the more wrinkles there are.
But even though all we can see when we look at a human brain is lots and lots of cortex regions, you still can’t see the insula cortex. That’s because it folds inwardly and gets covered up by the other lobes. The only way to see it is to cut a brain in half and look at the folds from the inside, as shown in the picture below. In this picture the insula cortex has been colored green, brown, and blue, and you can see how it has folded inside the brain whereas the rest of the cortex wrinkles up on the surface.