Most of us rarely remember our dreams, despite the fact that we spend on average more than two hours dreaming each night. Research has shown that dreams play a vital role in our health and mental well-being, and there are some strange phenomena associated with dreaming which can also help us learn about the science of dreams. 

Over the years, many different theories have been put forward about why we dream, and what these dreams mean, but until recently we have not had the technological capabilities to test these theories. Cristina Marzano and her colleagues at the University of Rome published a paper in the Journal of Neuroscience in 2011 which measured the brainwaves of participants at different stages of sleep and recorded whether or not they remembered their dreams. Interestingly, the brain activity that was recorded looked just the same as you would expect to see for a participant retrieving and recording memories whilst he or she was awake. The same research team found that vivid, emotionally intense dreams are linked to two specific parts of the brain – one that deals with processing and remembering emotions, and one that plays a role in memory. Other recent research has backed up this connection between dreaming and emotion – it has been found that a lack of ‘dream sleep’ influences our ability to process complex emotions in our everyday lives. 

All of this research taken together leads to the theory that dreams help us to process emotions by constructing memories of them, so that while the content of our dreams may not be real, the emotions we experience in them are. Dreams help us to work through and process our emotions, particularly negative ones, showing that there is a scientific reasoning behind the advice to “sleep on it” when making an important decision. 

Most of this important dreaming occurs during REM (rapid eye movement) sleep. There are, however, four other phases of sleep, all of which are non-REM. During REM sleep we normally lose the use of our muscles and are essentially paralysed – this is so that whilst we are dreaming we don’t act out the things that we dream. Many cases of REM behaviour disorder have been recorded, in which the brain of the sufferer fails to properly immobilise the body so that these people act out their dreams, often causing harm to themselves or others. Some particularly strange cases have been recorded, in which sleepwalkers have been observed eating and even cooking during sleep, although this sleepwalking occurs during non-REM sleep and its causes are not well understood. Even more bizarre are the reported cases of ‘sexsomnia’. The research here is limited as it often relies on self-reports, but there are many cases of sufferers engaging in various sexual activities only to have no recollection of it upon waking the next day. There have been at least five controversial cases in which men have been acquitted of sexual assault charges because they claimed they were asleep during the attack. 

However, an even more common sleep disorder, sleep paralysis, is essentially the opposite of this. Sleep paralysis is the experience of being unable to move or talk, which occurs most often when someone is waking up, although it can also occur in the early stages of sleep. The paralysis can last anywhere from a few seconds to a couple of minutes. It can be a frightening experience because you are entirely conscious throughout – just unable to move. It is very common for sufferers to experience the sensation of breathlessness or something restricting their breathing. 

What makes the paralysis more frightening is that many sufferers report experiencing hallucinations at the same time – in 1999, a study reported that in 75 per cent of students who had experienced sleep paralysis, hallucinations had accompanied the experience. Particularly common is the sensation of another presence in the room, often of a supernatural or demonic kind. 

This has led to sleep paralysis finding its way into folklore – for example, in China it is known as “the ghost pressing down on you”, and in Mexico “the dead climb on top of you”. 

Despite a few rather strange and curious sleep disorders, most of which are easily treatable, sleep is undoubtedly of vital importance for mental health and well-being. If nothing else, this gives you the perfect excuse for a nap.

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