I know there have been cases where a person can have ‘total recall’ after an injury (assuming head)… but why can’t our brains just dig and remember everything?
In: 5
[Probably to prevent insanity.](https://gizmodo.com/our-brains-deliberately-make-us-forget-things-to-preve-1543846375)
Memory is “stored” in the pattern of connections between neurons. Think of your brain like a map of a city, and a memory isn’t an *address* so much as the route you take to *get* to the address. As you walk along that path, you build the memory. Each “place” along the way is some aspect of the memory – like you have a friend named Bob and when you think of a memory of Bob, you walk down “Bob” street, and you went to a movie with Bob so you also go down the “movie” street and it was a Marvel movie so you also go down several Marvel character streets.
Multiple memories may go down parts of the same path, but the unique series of connections between neurons is what makes that memory unique. As you build the memory the first time, you don’t grow new neurons, but your neurons build new connections between them. The more often you revisit a memory, the stronger those connections get. If you don’t revisit a memory often, the connection gets weaker until it goes away, and you lose the memory.
And your brain doesn’t really know where it’s going when you begin the journey. The chemical signals propagate out among all the connections, but their strength dies off with weak connections so the chemical signal ends up following the strongest connections along that path. In the city of your mind, the chemical signal wanders along wherever it can and doesn’t wander where it can’t, and as it wanders the memory is remembered.
You might imagine that if you have a *lot* of memories – too many memories – the paths become too convoluted and it’s a lot easier for the chemical signal end up following the wrong path. It gets harder and harder to control the signal and limit it to only the one unique path that is the one memory you want. And that can lead to insanity. Your brain gets too confused trying to keep everything organized, trying to remember what’s important vs what isn’t important, trying to remember only one thing at a time, trying to separate pieces of memory so they don’t blend and blur together.
Also, maintaining the connections between neurons takes energy and resources. For the vast majority of life on Earth, resources were hard to get. It just wasn’t worth the calories to maintain memories and the connections for memories that weren’t important. If it didn’t help you survive by avoiding danger, getting food, finding a mate, etc. it wasn’t worth keeping.
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