Non-rapid eye movement sleep 3D maze. Participants were then trained in the maze for 4 hours and later, during the various sleep cycles of nonREM sleep, REM sleep and wakefulness, they were scanned twelve times using a PET scan during the night. The PET scan demonstrated a higher blood flow in the hippocampus during SWS/non-REM sleep due to the training from the previous day while the control group exhibited no increased blood flow and they had not received the training the prior day. The brain activity during sleep, according to this study, would show the events of the previous day do make a difference.
Rapid eye movement sleep allows the brain to travel further along unrealistic and peculiar trains of thought. Some dreaming can take place during non-REM sleep. “Light sleepers” can experience dreaming during stage 2 non-REM sleep, whereas “deep sleepers”, upon awakening in the same stage, are more likely to report “thinking” but not “dreaming”. Certain scientific efforts to assess the uniquely bizarre nature of dreams experienced while asleep were forced to conclude that waking thought could be just as bizarre, especially in conditions of sensory deprivation. Because of non-REM dreaming, some sleep researchers have strenuously contested the importance of connecting dreaming to the REM sleep