They’re certainly stored somewhere as it’s quite common to have a fragment of an old dream flash across your memory. In fact it’s just happened to me, I suddenly remembered part of a dream I had last week. It was only a couple of images, there was more to it last week that I’ve forgotten. Dream memory is weird, you recall an image, a feeling, it starts coming together, you almost recall more then it’s gone and all you’re left with is the original image.
But which part of the brain are memories of dreams stored in? It can’t be the same part as normal memories otherwise the two would constantly be getting mixed up and we wouldn’t know a genuine memory from a dream one. In fact how does the brain distinguish the two? How do we know that one memory is from a dream while the other really happened?
I’m not an expert on memory storage, but I don’t agree with your premise. Why would you need a special place to store dream memories? A memory is a memory, and I can easily distinguish a dream memory from a reality memory.
For one thing my dreams are usually so bizarre they can’t possibly be real. BTW, to answer your question, according to thismemories are mainly stored in the frontal lobes.
Because they don’t seem to be stored in the same way. To begin with, with typically don’t remember what we just dreamed off unless the dream was very impressive or if we make an habit of trying to remember our dreams first thing after waking up, while we remember pretty well what we did 5 minutes ago? And they can’t be just stored in short term memory since, as the OP mention, we can suddenly remember them later in the day when something trigger this memory, which doesn’t happen with regular memories, either. Maybe the “storage” is the same, but at least the access method to this storage must be different.
ETA : In fact, I actually did one day suddenly remembered a real life and forgotten very old memory very vividly (including taste and texture). But it’s the only time it happened in my life, while it’s pretty common with dreams.
The only thing that lets you know that it was a dream is remembered information that it was a dream. Or possibly that your mind recognises that it is so characteristic of dreams that it must have been a dream. But if the former, you simply remember the dream along with a tag that says “dream”. No special memory needed.
The difficult problem is that it is the same device (our brain) that is both doing the remembering and deciding what it is that is being remembered. We are thus always correct. Even remembering that the memory is an old memory is our brain telling itself that it is an old memory. You can’t know this is true, except by total trust of your memory. You could dream that the dream is an old dream. And so on all the way down.
The further problem is that there is a lot of evidence that dreams are associated with the memory process. So even more self referential questions. Dreams may in part stem from the memory system operating. So how you interpret memories of the memory system working becomes a highly self referential question.