Sleep Cycles

In this text, you will learn more about sleep cycles and whether or not dreams have a function. The reference for this text is the book by Robert J. Hoss, entitled The Science of Dreaming – The science of dreams.

Figure 1 illustrates the sleep cycles of a normal person over a period of 8 hours. The horizontal line is the hours of sleep, while the vertical lines are the sleep stages.

In simple terms, the graph shows that each person cycles between NREM (deep sleep) and REM (shallow sleep) several times during the night. This cycle happens during sleep in periods of about 90 minutes.

We typically experience four to six sleep cycles (between REM and NREM) in an eight hour night. And even so, we remember – if we remember – few dreams.


Do dreams have a function?

Some studies have shown that sleep and dreams are linked to learning and repair of the body and mind. If we don’t have the precise amount of REM sleep, the body will recover the “lost” amount by increasing sleep first, and thus recovering the lost amount of REM sleep. This suggests that dreams are important.

It has been observed that lack of sleep and dreams causes effects such as: daydreaming (visual and auditory hallucinations); interference with memory and learning; loss of associations; loss of skills that require full attention; difficulty maintaining a complete train of thought; irritation. For this reason, it is currently thought that the lack of REM sleep or dream sleep is related to the restoration of mental health.

Dream sleep appears to play an important role in revitalizing new and old experiences so that they remain in long-term memory.

Alan Hobson, from the Massachusetts Mental Health Center, demonstrated with an experiment with rats what would be one of the functions of sleep with dreams: a study demonstrated that the same neurons activated when a rat explores the maze are repeated when the rat dreams. In this way, the rat’s brain would be repeating the experience while dreaming, in order to memorize it.

Research from Israel has shown that consistently disrupting dreaming sleep one night blocks learning, whereas disrupting non-dreaming sleep does not.

So sleep and dreams apparently play critical roles in memory and learning, as well as reducing stress and generally keeping our mental health in good shape.

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