People can come up with plausible sounding explanations, some rooted in whatever level of neuroscience they have, but the truth is we have no earthly idea about how the brain stores memories in different ways and especially why. Best we can do is damaging different parts (or more usually looking at people's brains that got damaged naturally in accidents) and seeing how people's behaviour changes, and experiments on the brains of much smaller animals.

The brain does not store any memories properly. People rely far too much on old memories.

Who's to decide what "properly" actually means in an evolutionary context? At some point in the past, this behavior either gave us a survival advantage in some way, or at the very least, didn't hurt our survival chances.

The brain is lazy.

As a rule of thumb, the brain is better at storing information that is more attached to strong emotions, or anything that you repeat often.

When a traumatic event happens, the brain will try to attach it to one, maybe two things that are easy to spot and remember (say, a man in a black hoodie wearing flip flops), so that when those specific triggers happen to be around again (black hoodie, flip flop walking sound), there is enough information for the rest of the body to react as soon as possible.

This has a lot to do with survival. Think like a caveman. You hear a growl, you turn back and see a tiger or jaguar, readying a pounce. If you survive, the next time you hear a similar enough growl, you won't even need to look back, it'll be enough to trigger your fight-or-flight response and get you moving earlier. You don't need to remember what kind of predator it was, only that it was dangerous.

One theory is that your brain doesn’t want or need it. The intensity is such that it nopes out. Another is that the body is busy with physical survival, a bad car crash (sans TBI) being the classic scenario in which memory loss is common, and all resources are thus diverted.

Memory is not a video recorder. In addition, it’s a fickle bitch at times.

Emotion can enhance memory. You’ve clearly read that data. Emotion can also nudge memory into something inaccurate or distort the fuck out of memory, cognitive dissonance and personal biases being what they are. Worse, false memories are real.

Take a deep dive into the false memory data. It begins with Elizabeth Loftus back in the 90s and marches forward from there. How do you tell the difference between a false memory and a real memory? Short answer: you can’t. Sure, people and documentation around someone can prove a memory false but that won’t necessarily make the memory feel false to the person holding onto it.

Attention is a key component to encoding a memory in the first place. How focused is your attention if your car is airborne and you’re waiting for it to finish crashing? Maybe focused. Maybe not.

There are Masters Degrees in cognitive science devoted to memory studies and they still don’t have it figured out. But there’s plenty to read on the topic.

Am I missing something here? All the comments seem to be responding to a completely different post? All I see is "I don't understand science or biology well just fyi"

I remember a story of a woman with a perfect memory (some gene mutation), the problem was that she remembered EVERY conflict she ever had with anyone. She was alone, because once she had an issue with anyone she was not able to forgive them, because in her memory it was always as crisp (and as painful) as if it happened minutes ago.

I am not an expert, but I feel like the brain might miss details of traumatic memories on purpose, to make it easier to deal with.

It's simple. The brain doesn't store any memory properly.

Cool Kurtzgesagt video: https://m.youtube.com/watch?v=PqtggjVAi8M

Is this what's really happening? I was under the impression that PTSD victims retain their traumatic memories to a problematic point that inhibits the formation of new ones. Or recalling other non traumatic stuff

what a pointless post

Fear prevents your brain from realizing that the experience has ended.

Your brain doesn't have that normal "This is starting, this is in progress, this has ended," progression.