Rapid eye movement
In mammals and birds, sleep can be divided into two categories. In one of them, the eyes move rapidly. This is called REM-sleep (from rapid eye movement). Most dreams take place in this phase. REM-sleep occurs normally at intervals throughout the night. The periods of REM-sleep increase in length in the second half of the night. REM-sleep was first discovered in 1952-53.
The other category, where this movement of the eyes does not happen, is called NREM-sleep (Non-REM sleep). Usually, dreams do not occur during this time. There are three or four stages of NREM-sleep. Stage I is just barely sleeping, or dozing. Stage II is also light sleep. Normally, in adult humans, about half of the time spent asleep is spent in light sleep. Stages III and IV are called deep sleep. Deep sleep is necessary for growth and healing. It can be quite difficult to awaken someone who is in stage III or stage IV sleep. Sometimes stages III and IV are combined and called stage III.
Adult humans normally sleep in cycles of 90 to 110 minutes each. The night's sleep can be 4 or 5 of these cycles. Each cycle includes, in this order: stage I, stage II, stage III (IV), stage II and REM.
REM and dreams[change | change source]
Rapid eye movement sleep is associated with dreaming. Waking up sleepers during a REM phase is a common way to get dream reports. 80% of typical people can give some kind of dream report under these circumstances. Sleepers awakened from REM tend to give longer more narrative descriptions of the dreams they were experiencing. They estimate the duration of their dreams as longer.
Lucid dreams are reported far more often in REM sleep. The mental events which occur during REM usually have dream 'hallmarks' including narrative structure, convincingness (like waking life), and instinctual themes.
The function of REM sleep is not well understood.
References[change | change source]
- Solms 1997. The neuropsychology of dreams, pp. 10, 34.
- J. Alan Hobson, Edward F. Pace-Scott, & Robert Stickgold 2000. Dreaming and the brain: toward a cognitive neuroscience of conscious states. Behavioral and Brain Sciences 23.
- Ruth Reinsel, John Antrobus, & Miriam Wollman 1992. Bizarreness in dreams and waking fantasy. In Antrobus, John S. & Mario Bertini (eds) The neuropsychology of sleep and dreaming. Hillsdale, NJ: Lawrence Erlbaum Associates. ISBN 0-8058-0925-2
- Stephen LaBerge 1992. Physiological studies of lucid dreaming. in Antrobus & Bertini (ed) The neuropsychology of sleep and dreaming.