Meghan Rosen writes:

You’d never guess that Elyse G. has a black hole in her brain.

Meet her on the street, and it’d be impossible to tell she’s lacking a chunk of neural tissue about the size of a small fist.

Looking at her brain scans is a different story. It’s as if someone has knocked over a bottle of ink. The darkness pools inside her skull near her left ear, a puddle of fuliginous black. Inside the splotch, there’s no white matter or gray matter, no blood vessels or tissue at all.

Elyse says you don’t have to be a neurosurgeon to spot what’s different about her brain: “There’s a big honking piece missing!”

Scientists can’t say exactly how it happened. It’s possible that sometime long ago, perhaps due to a stroke before or shortly after birth, a portion of Elyse’s brain died and then ultimately disappeared, leaving behind only liquid — brain tissue swapped for a fluid-filled void. Her sister has one too.

Elyse and her sister, Martha M., who are not using their full names to maintain their anonymity, look and act perfectly ordinary. But each lacks most of a temporal lobe, and each in a different hemisphere. Elyse is also missing part of her brain stem. The women are two of who knows how many people living their lives without brain structures generally thought to be crucial.

Martha, now age 59, didn’t know her brain was different until she was a teenager. Elyse, who will turn 61 this year, found out in graduate school. Two sisters. Two brains. Two black holes. When MIT cognitive neuroscientist Evelina Fedorenko’s team first learned about the duo, “we were all kind of blown away,” she says. [Continue reading…]