Dreaming[edit]
Rapid eye movement sleep has since its discovery been closely associated with dreaming. Waking up sleepers during a REM phase is a common experimental method for obtaining dream reports; 80% of neurotypical people can give some kind of dream report under these circumstances.[44] Sleepers awakened from REM tend to give longer more narrative descriptions of the dreams they were experiencing, and to estimate the duration of their dreams as longer.[8][45] Lucid dreams are reported far more often in REM sleep.[46] (In fact these could be considered a hybrid state combining essential elements of REM sleep and waking consciousness.)[8] The mental events which occur during REM most commonly have dream hallmarks including narrative structure, convincingness (experiential resemblance to waking life), and incorporation of instinctual themes.[8]
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.[11][16] However, people woken up during sleep do not report significantly more bizarre dreams during phasic REMS, compared to tonic REMS.[45] Another possible relationship between the two phenomena could be that the higher threshold for sensory interruption during REM sleep allows the brain to travel further along unrealistic and peculiar trains of thought.[45]
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.[45][47] Because of non-REM dreaming, some sleep researchers have strenuously contested the importance of connecting dreaming to the REM sleep phase. The prospect that well-known neurological aspects of REM do not themselves cause dreaming suggests the need to re-examine the neurobiology of dreaming per se.[48] Some of the old guard in paradoxical sleep research (Dement, Hobson, Jouvet), however, tend to resist the idea of disconnecting dreaming from REM sleep.[8][49]