system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What happens in my brain when I remember something that I had previously forgotten?

For example when you are trying to think of a song, you spend 10 minutes searching your brain for it then the next day the name randomly pops into your head.
gpt
Nerve cells connect with each other via synapses. We know that these synaptic connections become stronger if the nerve cells are very active (fire often). The synapses become weaker if the nerve cells fire less often. This phenomenon is called synaptic plasticity.

The theory is that if we memorize something, new synaptic connections between nerve cells form. Depending on how often we use the same memory, the synapses will become stronger or weaker.

If a synaptic connection is lost or weakened, the memory is lost as well. For long term memory, it seems that connections are never really lost, it can just become more difficult to access and retrieve the information. This is because our brain constantly changes. In order to retrieve the same information reliably, you need to have the correct context of the information and the correct 'brain state' that allows you to make those associations.