Livewired: The Inside Story of the Ever-Changing Brain

play a loud beep to someone, and use electrodes on the scalp (electroencephalography) to measure the brain’s response. In a normal adult, the beep elicits an electrical response that can be measured clearly over the auditory cortex, but is smaller or absent over the visual cortex. Now compare this with what you would see in a six-month-old child: t

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.

This is why people become desensitized (or tolerant) to a drug: the brain comes to predict the presence of the drug, and adapts its receptor expression so it can maintain a stable equilibrium when it receives the next hit.

Imagine you could swallow a capsule that would renew your brain plasticity: this would give you the capacity to reprogram your neural networks to learn new languages rapidly and adopt new accents and new views of physics. The cost is that you’d forget what came before. Your memories of your childhood would be erased and overwritten. Your first love

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.

Tossing facts at an unengaged student is like throwing pebbles to dent a stone wall. It’s like trying to get Fred Williams to absorb tennis.

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.

Some years ago, the writer Stewart Brand proposed that to understand a civilization, you need to look at multiple layers functioning simultaneously at different speeds.22 Fashion changes rapidly, while the business pursuits in an area alter more slowly. Infrastructure—such as roads and buildings—evolves more gradually. The rules and laws of a socie