Roundabout

Here's a paragraph from a Slate.com article by the terrific Emily Yoffe about being a daycare worker:

A recent science column in the Wall Street Journal described a study that found that you don't even have to like kids to have your brain's fusiform gyrus produce instantaneous good feelings when you see a baby's face. Standing in the darkened Robins' room, listening to their deep breathing, their sighs, their occasional snurtles, I felt a profound sense of peace. I'm sure some gyrus in my brain was telling me there is no better sound than a roomful of sleeping babies.

In knew there was more than one gyrus in the brain, because I'd read about the angular gyrus (which, among other things, is intimately involved with making words comprehensible). I did not, however, have any idea of what a gyrus might actually be.

If I had bothered to think about it, it would have occurred to me that the word is related to "gyrate" and even "gyre", not a very common English word but still one which exists; I'd read recently (in "The World Without Us") about the Northern Pacific Gyre, which is basically a floating oceanic garbage dump bigger than the state of Texas.

"Gyrus" and its relatives are from Greek "gyros", "ring, circle". To gyrate, then, is to move in a circle, and Northern Pacific Gyre is a sort of flat whirlpool which draws all that bobbing nautical garbage into itself and traps it there. The Greek meat sandwich called a gyro also comes from this word; it's named for the rotations of the spit on which the lamb is cooked.

A gyrus in the brain is a convolution, a swirl of grey matter with a specific function. The angular gyrus, as I said, is tied primarily to language; its name comes from its shape, which is rather rhomboidal. The fusiform gyrus contributes to the recognition of colours, words, numbers, and, as the Yoffe quote suggests, faces. "Fusiform" means "spindle-shaped", from Latin "fusus", "spindle. This is, predictably, where the English word "fuse" comes from as well.