Your whole brain reacts to events

The idea that your brain reacts to events in the world is a myth. The idea supposes that you go through your day with parts of your brain in the off position, but when something happens around you, those parts become active and light up with activity.

But the brain doesn't work by stimulus and response. All your neurons are firing all the time at various rates. Your brain uses all its available information to predict what will happen next and make corrections outside of your awareness.