Oneiric Time Travel

It long has been known that sleep helps incorporate and reinforce useful recent memories into long-term storage while pruning out unimportant memories. This is why it is helpful to sleep after cramming for a test the next day rather than studying through the night – quite aside from the more obvious effects of lack of sleep. You will remember more. Dreams are part of that memory reinforcement process even when we don’t consciously remember those dreams the next day. Dreams connect recent memories with old ones in imaginative ways and thereby deepen their integration into who we are. This is generally a positive experience when we remember a dream at all, but of course nightmares do happen. They happen to everyone sometimes but are especially common among those with PTSD. 52% of combat veterans report frequent nightmares compared to 3% of civilians. Once again, everyone has them; the difference is frequency.

The Nightmare (1781) - Henry Fuseli 

 
It appears that dreams follow a chronological pattern. According to a recent study dreams early in the night are dominated by recent memories: events people, and experiences of the previous day. As the night wears on, dreams get associated with ever older memories. My own experience supports this anecdotally. My dreams lately have been full of people and places I know from long ago – including family members deceased for decades. We tend to remember only those dreams during which we wake up, and I usually wake up suddenly in early morning daylight. The reason is a cat who habitually enters my room at that time and jumps on me. It is no wonder I remember dreams that are tied to old memories. That is when they are scheduled to occur.
 
The researchers determined which type of dream-memories were associated with which sleep stages by waking 20 volunteers 12 times per night. I hope the volunteers were well-paid because that would be really annoying. The cat is annoying when he does it once.
 
I don’t mind these nostalgic dream trips however. I’m almost always in my 20s in them for one thing. (I never actually state an age, but I can tell.) It’s nice to feel that way again, if only in dreams. It is also nice to have a visit, of sorts, with people and pets from my youth. Dreams about yesterday on the other hand are bound to feel more mundane. I don’t plan to be awakened 12 times to test this though. If the cat tries it on his own, I’m locking him out of the bedroom.
 

Blondie - Dreaming