my understanding of the brain is that all areas of the brain are active through out the night. what changes is the kind of brain waves during sleep vs awake. (alpha, beta...)

example the thalmus is active during the daytime. its the pain center. its also active during sleep ever dream of getting hurt in a dream and during that it actually feels like you got hurt.

the hippocampus is the memories and emotions center for the brain. its active during awake hours and when alsleep. (where do dreams come from.. our remembered experiences and emotions related to those experiences and our imaginations...)

my point there are many many parts of the brain that are active 24/7 during sleep/ waking or under stress or relaxation.

my suggestion is maybe do a research project or join a college biology class that teaches all about the brain and how it functions and what each part of the brain does. the brain is an amazing organ and I really enjoyed my college health classes. I was amazed at just how much the brain continues to work even when we are asleep.