title: Dreaming during non-rapid eye movement sleep in the absence of prior rapid eye movement sleep.
abstract: OBJECTIVE
  There is a long-standing controversy surrounding the existence of dream experiences during non-rapid eye movement (NREM) sleep. Previous studies have not answered the question whether this "NREM dream" originates from the NREM sleep mechanism because the subject might simply be recalling experiences from the preceding rapid eye movement (REM) sleep.
  
  
  METHODS
  We scheduled 11 healthy men to repeat 20-minute nap trials separated by 40-minute periods of enforced wakefulness across a period of 3 days. At the end of the nap trial, each participant answered questions regarding the formal aspects of his dream experiences during the nap trial, using the structured interviews.
  
  
  RESULTS
  We obtained a total of 172 dream reports after naps containing REM sleep (REM naps) and 563 after naps consisting of only NREM sleep (NREM naps). Dream reports from NREM naps were less remarkable in quantity, vividness, and emotion than those from REM naps and were obtained more frequently during the morning hours when the occurrences of REM sleep were highest.
  
  
  CONCLUSIONS
  These results suggest that the polysomnographic manifestations of REM sleep are not required for dream experiences but that the mechanisms driving REM sleep alter experiences during NREM sleep in the morning. A subcortical activation similar to REM sleep may occur in human NREM sleep during the morning when REM sleep is most likely to occur, resulting in dream experiences during NREM sleep.
authors.affiliation: Department of Psychophysiology, National Institute of Mental Health, National Center of Neurology and Psychiatry, Kohnodai, Ichikawa, Chiba, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Suzuki
authors.forename: Makoto
authors.initials: M
authors.lastname: Uchiyama
authors.forename: Hirokuni
authors.initials: H
authors.lastname: Tagaya
authors.forename: Akiko
authors.initials: A
authors.lastname: Ozaki
authors.forename: Kenichi
authors.initials: K
authors.lastname: Kuriyama
authors.forename: Sayaka
authors.initials: S
authors.lastname: Aritake
authors.forename: Kayo
authors.initials: K
authors.lastname: Shibui
authors.forename: Xin
authors.initials: X
authors.lastname: Tan
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Kamei
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Kuga
mesh_terms: D000328:Adult; D004325:Dreams / Q000502:physiology*; D004562:Electrocardiography; D004576:Electromyography; D006801:Humans; D008297:Male; D008550:Melatonin / Q000032:analysis; D017286:Polysomnography; D012463:Saliva / Q000737:chemistry; D012894:Sleep Stages / Q000502:physiology*; D012895:Sleep, REM / Q000502:physiology; D011795:Surveys and Questionnaires; D013997:Time Factors
chemical_list: D008550:Melatonin