Your Brain: The Missing Manual

Chapter 10. The Developing Brain

You can't spend 222 pages exploring the quirks of your brain without starting to wonder exactly how it was created. Of course, you know some of the circumstantial details—the man, woman, lingerie part of the equation—but that hardly accounts for the 100 billion tiny electrical links that create love, consciousness, and run on sentences. To get the full picture, you need to go back to the very first hour of your life, and then you need to go back a bit further. In fact, you need to start at the very beginning of your beginning, the icky moment when your parents got together, did unspeakable things, and set your brain on an irreversible course from a single cell to reading this book.

In this chapter, you'll take that journey and see how your brain developed from conception, passed through the rocky waters of teenage life, and ended up in the middle of adulthood (if indeed you've made it that far). You'll see how biological processes work like a sculptor to chisel away nearly half your neurons before you've had a chance to use them. Finally, you'll look forward and consider how your brain changes as you glide into the twilight years of old age.

Before Birth

You know the script. Tragically outdated clothes, a sordid night of passion, and moments later a single fertilized cell was on its way to becoming you.

Early on in your development, when you were little more than a teaspoon of jelly, your brain began to form. It started out as a disk of rather ...