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 REM sleep, and the existence of similar PGO waves is thus inferred.) These waves occur in clusters about every 6 seconds for 1–2 minutes during the transition from deep to paradoxical sleep. They exhibit their highest amplitude upon moving into the visual cortex and are a cause of the "rapid eye movements" in paradoxical sleep. Other muscles may also contract under the influence of these waves. Research in the 1990s using positron emission tomography (PET) confirmed the role of the brain stem and suggested that, within the forebrain, the limbic and paralimbic systems showed more activation than other areas. The