Our brain is a huge highway system of neurons, with about one quadrillion (1015) synapses where roads cross. Like cars on a map, information can flow through this system many ways. But, again like roads, there’s always one way that’s fastest. How does information choose the fastest way?
The answer is that the brain learns to efficiently route information through trial and error. And in a process very similar to natural selection, the pathways that are proven to work survive and those that don’t are pruned from the system.
Here’s how it works:
First, early in our prenatal development, our brain lays neural pavement, including freeways, arterial roads, roundabouts, and culs-de-sac. Now, in the absence of GPS and Google Earth, the only thing to do is drive the roads blindly, which we do through infancy. Every time a baby receives input, many cars travel many roads, some choosing efficient paths and many hitting roundabouts and roadblocks.
Every time information travels a route, it trains the synapses along this route to fire slightly faster, like optimizing the traffic lights at crossroads. And so the roads that correctly transmit the information gain efficiency. Eventually the proven routes become significantly faster than the others and the inefficient routes are closed off entirely.
Now when a stimulus enters the system, it knows exactly where to go and follows the same, efficient route every time.