The Five Stages of Sleep

Misconceptions regarding seep and brain activity have prevailed since times immemorial. While most people tend to think that sleep is the period when the activity in the brain reduces or is minimal, research and study have proved otherwise. When a person is asleep, activity in the brain has been recorded to be more wide-ranging than when a person is awake and while sleeping, a person goes through various dissimilar stages of sleep.

Typically, when a person sleeps, the pattern involves five stages of sleep. The first stage of sleep is a lighter stage when the person is drifting in and out of sleep and can be easily awakened. During the first stage, there is rapid eye movement (REM).

The second stage of sleep is characterized by the slowing and stopping of eye movement with the simultaneous slowing of the brain waves.

During the third stage which is a deeper sleep stage, there is an intermingling of the slow delta brain waves with the faster waves. The stage of ‘deep sleep’ commences with the third stage.

The fourth stage of sleep is the period when the brain is entirely involved I the production of delta waves. This is the stage when the ‘deep sleep’ stage is optimal and waking up a person from this stage is difficult. The deep sleep stage is characterized by reduced REM and muscle activity and is also the stage when children are most likely to experience bedwetting or problems of sleepwalking.

The REM is the concluding and final stage of sleep when there is also rapid breathing. There is the rapid jerky movement of the eyes during this stage and there is an increase in the brain wave activity during this period.

The stages of sleep or the sleep processes are measured with the help of certain machines and instruments. The EEG or the electroencephalogram is a machine used to measure the electrical activity from one single area of the brain and is termed as the gross brain wave activity. The EMG or the electromyogram is a machine that helps to measure muscle tone. The EOG or the electrooculogram is the machine that is used for recording the pace of the eye movements while a person is asleep. It is important to note that while all three machines are important in studying the sleep processes, the EEG plays a vital role in distinguishing between the various sleep stages.

The EMG and the EOG are important in distinguishing the RAM or the rapid eye movement stage from the other four stages of sleep. During the last and the final sleep stage, besides the REM, there is also a quick and striking loss in the muscle tone, an activity that is measured by the EMG.

The importance of the EOG and the EMG can also be gauged from the fact that it is the fifth or the REM stage which has been associated with the aspect of dreams (Dement & Kleitman, 1953), and dreams are considered extremely important in the domain of psychology.

It is important to note that on any given night, a sleeper can commence with the first stage of sleep and advance to all the other stages, and then experience all the stages back again, except that the first stage is replaced by the REM. This recurrent sleep activity Dement (1978) explains to be the reason why sleepers could experience “as many as ten or twelve dreams every night” (Dement, 1978, p. 37; quoted in Pinel, 1993).


Dement, W.C. (1978). Some must watch while some must sleep. New York: W.W. Norton.

Pinel, J.P.J. (1992). Biopsychology. Needham Heights, MA: Allyn & Bacon.

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