Why Do We Lose Things When We Get Old?

Imagine your brain is a giant toy box. When you are young, the box is brand new. Every time you learn something new, like how to ride a bike or what an apple tastes like, it gets a special spot with a bright label. But as you get older, that toy box starts to fill up!

When you are little, your brain does a lot of cleaning. It throws away old toys you don't use anymore so you have room for new ones. This is called synaptic pruning. Sometimes, it throws away too many good toys by mistake! If you stop playing with your ball much after you turn eighty, the brain might decide the ball is just clutter and toss it out.

Also, things get dusty inside the box. Tiny bits of dust called plaques start to stick together on the walls. These plaques block the lights so the messages don't travel as fast. Your memories are still there, but they are harder to find because the path to them is a bit messy. So, you forget where you put your keys not because they vanished, but because your brain forgot which drawer holds the 'key' light.