While We Were Sleeping

by Zoë Pollock

Sunny Biswas takes stock of the year, from a neurobiological perspective:

It turns out that in a couple of parts of the brain, neural stem cells are constantly giving birth to new neurons that travel around and plug into already existing networks. Sometimes they're replacing dying neurons and sometimes they're just helping a part of the brain grow. (A lot of neurons don't get replaced at all, though, so we're about half a ship of Theseus). There's a body of recent literature that suggests that this is how adults form new memories. Some of it also says that depressed people are worse at doing thisimportant chunks of our brains stay locked into these self-destructive patterns, while healthy people have brains that are malleable enough to change. ...

I read about neural stem cells and think about how different I am from even a few years ago, and I get the weird feeling that I was right when I was little, that I'm the most recent in a long line of not very good impersonators of myself. Science (science!) confirms that parts of me are here now that weren't there even a little while ago (and that parts of me that were there before are gone forever). In other words: one night someone else went to sleep and woke up as me.