system
Given the following post, respond as if you're commenting on Reddit:
human
How does my brain come up with people I have never seen / heard of / met before while I am dreaming?
gpt
The premise of this question is flawed. There's presently no way to test whether the people you dream about are people that you have seen, heard, or met before.

We have no way of cataloging everyone that we've ever encountered, and certainly no way of comparing such a catalog to people that appear in dreams, even if such a catalog did exist.

We also don't remember most of our dreams and have imperfect recall of those that we do, so there's no way of comprehensively studying all of the people that appear in dreams. The flow of information between the frontal cortex and hippocampus is different in sleep, as compared to wakefulness. The sleeping brain seems to be more concerned with consolidating or sorting useful and salient memories from the previous periods of wakefulness, as opposed to creating new memories of dreams. For whatever reason (possibly because dream content is not useful to remember), dreams are held in short-term memory, but are ordinarily not transferred to long-term memory. Therefore, we usually only remember dreams that we awaken from. It is common for people to report that details of dreams are transient, rapidly fading if no effort is made to rehearse the content. People will still remember that they had a dream, but won't accurately remember its content anymore.

In other words, dreams are only remembered for any lasting time period if a person is awoken while they are in progress, and only then if the person makes some effort to rehearse the details. Given these required circumstances, and given the different functioning of the hippocampus during sleep, we are able to access only a small and almost certainly imperfect portion of dreams by simply asking people to recall what they dreamed about.