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1. Inside the Brain: Hacks 1–12 > 8. Tour the Cortex and the Four Lobes

Tour the Cortex and the Four Lobes

The forebrain, the classic image of the brain we know from pictures, is the part of the brain that defines human uniqueness. It consists of four lobes and a thin layer on the surface called the cortex.

When you look at pictures of the human brain, the main thing you see is the rounded, wrinkled bulk of the brain. This is the cerebrum, and it caps off the rest of the brain and central nervous system [Get Acquainted with the Central Nervous System].

To find your way around the cerebrum, you need to know only a few things. It’s divided into two hemispheres, left and right. It’s also divided into four lobes (large areas demarcated by particularly deep wrinkles). The wrinkles you can see on the outside are actually folds: the cerebrum is a very large folded-up surface, which is why it’s so deep. Unfolded, this surface—the cerebral cortex—would be about 1.5 m2 (a square roughly 50 inches on the side), and between 2 and 4 mm deep. It’s not thick, but there’s a lot of it and this is where all the work takes place. The outermost part, the top of the surface, is gray matter, the actual neurons themselves. Under a few layers of these is the white matter, the fibers connecting the neurons together. The cortex is special because it’s mainly where our high-level, human functions take place. It’s here that information is integrated and combined from the other regions of the brain and used to modulate more basic functions elsewhere in the brain. The folds exist to allow many more neurons and connections than other animals have in a similar size area.


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