Livewired: The Inside Story of the Ever-Changing Brain

You pay attention to the unexpected bang, the unforeseen brush on your skin, the surprising movement in your periphery.

For example, Jewish religious scholars study the Talmud by sitting in pairs and posing interesting questions to each other. (Why does the author use this particular word rather than another? Why do these two authorities differ in their account?) Everything is cast as a question, forcing the learning partner to engage instead of memorize.

The presence of acetylcholine at a particular brain area tells it to change, but it doesn’t tell it how to change. In other words, when the cholinergic neurons (those that spit out acetylcholine) are active, they simply increase plasticity in the target areas. When they’re inactive, there’s little or no plasticity.21

Your brain doesn’t want to pay the energy cost of spiking neurons, so the goal is to reconfigure the network to waste as little power as possible.

Consider one-trial learning, in which you touch a hot stove once and learn not to do it again. Emergency mechanisms exist to make sure that life- or limb-threatening events are permanently retained. But

Fundamentally, the brain is a prediction machine, and that is the driving engine behind its constant self-reconfiguration. By modeling the state of the world, the brain reshapes itself to have good expectations, and therefore to be maximally sensitive to the unexpected.

Reward is a powerful way to rewire the brain, but happily your brain doesn’t require cookies or cash for each modification. More generally, change is tied to anything that is relevant to your goals. If you’re in the far north and need to learn about ice fishing and different types of snow, that’s what your brain will come to encode. In contrast, if

At the extreme, this is how reptile visual systems work: they can’t see you if you stand still, because they only register change. They don’t bother with position. And such a system is perfectly sufficient: reptiles have been surviving and thriving for tens of millions of years.

She calmly told you once, and you got it. Why? Because it was salient to you. You loved your aunt, and you derived social benefit from knowing a new word and being able to ask for the fruit. This is one-trial learning not because of threat, but instead because of relevance.