system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How is data stored in the brain, and why is it difficult to forget traumatic memories?
gpt
Memory is something we're still learning about, but basically it seems to be stored in network form. Activation of a memory is a series of neurons firing and activating each other. While the hippocampus is a specific area very important in forming memories, storage is all over the brain. 

For trauma memories, let's get cognitive-behavioral. Ordinary forgetting happens passively over time as memories are not accessed and lack relevance. Trauma-related memories are often stored somewhat incoherently, and cause intense distress when recalled. The brain is both trying to figure out the puzzle and recoiling when it finds any puzzle pieces. Unfortunately, this often leads to furious attempts to avoid recalling the memory, which are about as effective as trying not to think about a polar bear (you already did.) This vicious cycle prolongs the memory and intensifies its effect.

Trauma-focused psychotherapy does the opposite. By recalling memories in detail, we force the brain to confront memories, tolerate them, and reprocess them in a more coherent way. By removing the avoidance part of the cycle, it allows for forgetting to take place.