Brain activity has nothing to do with dreaming; Some people insist that dreams do not happen in sleep, but false memories caused by confused thoughts when they wake up; Others suspect that the dreams in NREM sleep are caused by the invasion of REM sleep.
Extended data:
The cause of dreams
Scientific explanation: There is no conclusion about the cause and purpose of dreams in academic circles. It is generally believed that dreams are caused by some nerve impulses released by the brain when it processes information and consolidates long-term memory (just like dust raised during cleaning or information flow being processed), and are interpreted by conscious brains as bizarre vision and hearing.
First of all, Hobson and McCarley put forward the theory of "activation-synthesis" in 1977: the pons in the brain stem will constantly send out signals (PGO waves) to stimulate and activate the conscious part of the brain and make it synthesize a meaningful dream.
However, Solms later found that patients with brain stem injury still dream, while patients with parietal lobe injury (parietal cortex responsible for body sensation and sensory integration) do not dream. Perhaps the brain stem is only related to REM dreams, while the parietal lobe is related to REM dreams and NREM dreams.
Zhang Jie put forward the theory of "continuous activation" in 2004: one of the functions of sleep is to transform temporary memory into long-term memory, and REM stage deals with unconscious "procedural memory" instead of conscious "declarative memory" in eye movement (NREM) stage.