Dreaming during non-rapid eye movement sleep in the absence of prior rapid eye movement sleep.
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.
Suzuki
Hiroyuki
H
Department of Psychophysiology, National Institute of Mental Health, National Center of Neurology and Psychiatry, Kohnodai, Ichikawa, Chiba, Japan.
Uchiyama
Makoto
M
Tagaya
Hirokuni
H
Ozaki
Akiko
A
Kuriyama
Kenichi
K
Aritake
Sayaka
S
Shibui
Kayo
K
Tan
Xin
X
Kamei
Yuichi
Y
Kuga
Ryuichi
R
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
D008550:Melatonin