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 eye movements themselves may relate to the sense of vision experienced in the dream, but a direct relationship remains to be clearly established. Congenitally blind people, who do not typically have visual imagery in their dreams, still move their eyes in REM sleep. An alternative explanation suggests that the functional purpose of REM sleep is for procedural memory processing, and the rapid eye movement is only a side effect of the brain processing the eye-related procedural memory. Generally speaking, the body suspends homeostasis during paradoxical sleep. Heart rate, cardiac pressure, cardiac output, arterial pressure, and breathing rate quickly become irregular