system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What happens to your brain when you "blackout"?
gpt
Your short term memories are not being converted into long term memories.

You can be somewhat coherent at the time of a blackout, you just won't have an recollection of it.

It is similar to how you can be driving and suddenly realize you don't remember the last 20 miles.  Driving in boring and routine, and if nothing noteworthy occurs, those short term memories won't stick.  You are aware and alert the whole time, you just don't remember.