Dreams can be a gallery of images, ideas, emotions and feelings that take place subconsciously in your brain whilst you sleep. There are two main cycles of sleep which occur throughout the night, non-rapid-eye sleep (NREM) and rapid-eye sleep (REM), the latter consists of approximately 20%-25% of an average nights sleep and is it the stage we are more interested in.
REM sleep is characterised by continuous eye movements whilst asleep and during this time, the brains neurons represent a similar level of activity to waking hours and therefore this is when the majority of our memorable dreaming tends to happen. It is now widely accepted that dreams can and do occur during NREM sleep however these tend to be less vivid and less well remembered.
So what are dreams? They can last for a split second or for as long as 15 minutes towards the end of the night – when the REM cycle is longer. They can include people and places that you are familiar with or that you have never met or heard off before. Sometimes they can be as ordinary as events which have taken place or going to take place in your life, they can be your most private fantasies or even some of your innermost worries and secrets. The average person may have anywhere between 1 and 8 dreams per night, and as mentioned they tend to last longer as the night progresses.
There have been many experiments and findings from some of the worlds leading neurologists and psychologists looking into dreams, which have lead to a variety of hypotheses. The neurobiology has now more or less been understood, however to this day it is not definitively understood and as to why we have dreams, and what do they resemble, and is still a topic of scientific, philosophical and religious interest. Below are the most widely accepted theories which can all be found in more detail online.
• Activations synthesis Theory – Hobson and Mcarley,1976
• Continual-activation Theory – Zhang, 2004
• Dreams as excitations of long-term memory – Tarnow, 2003
• Dreams for strengthening of semantic memories – Stickgold et al, 2001
• Dreams for removing Junk – Robert, 1886
• Dreams for testing and selecting mental schemes – Coutts, 2008
• Evolutionary psychology theories of dreams – Revonsou, 2000
• Psychosomatic theory of dreams – Tsai, 1995
