Rapid eye movement sleep resemblance to waking life), and incorporation of instinctual themes. Sometimes they include elements of the dreamer's recent experience taken directly from episodic memory. By one estimate, 80% of dreams occur during REM. Hobson and McCarley proposed that the PGO waves characteristic of “phasic” REM might supply the visual cortex and forebrain with electrical excitement which amplifies the hallucinatory aspects of dreaming. However, people woken up during sleep do not report significantly more bizarre dreams during phasic REMS, compared to tonic REMS. Another possible relationship between the two phenomena could be that the higher threshold for sensory interruption during REM sleep
Non-rapid eye movement sleep Research has also shown that dreams during the NREM stage most commonly occur during the morning hours which is also the time period with the highest occurrence of REM sleep. This was found through a study involving subjects taking naps over specific intervals of time and being forcefully awakened, their sleep was separated into naps including only REM sleep and only NREM sleep using polysomnography. This implies that the polysomnographic occurrence of REM sleep is not required for dreaming. Rather, the actual mechanisms that create REM sleep cause changes to one's sleep experience. Through these changes, by morning, a sub-cortical