Decoding dreams: the science behind dreaming

Dreaming is a kind of mental state or altered state of consciousness which occurs during sleep. Often, they involve fictitious events that are organized into a loose story. They show that our brains are capable of generating entire worlds that are disconnected, but often draw inspiration from our waking environment. They have fascinated mankind since time immemorial and much has been speculated about their origins and purpose. Early accounts account of dreams from as far as 5000 years in Mesopotamia, set in clay tablets. Like many other things, they also have been subject to the fundamental human need to find a meaning in things that they don’t understand by inventing one. As such many ancient civilisations treated them as a means by which the future and prophesies can be communicated.

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Sigmund Freud

The scientific investigation of dreams only emerged during the late 19th century and primarily focused on factors that influenced the content of dreams. One of the first, and probably most recognizable dream theorists is Sigmund Freud (1856-1939), whose work is known for inexorably finding its way back to repressed sexual desires, regardless of the topic. Freud believed that dreams were means my which your body could preserve sleep from being disturbed by physical stimuli by causing “hallucinatory satisfaction”. These physical stimuli included things such as hunger, noise, light and to not alienate his core fans, sexual urges. In addition, he developed the discipline of psychoanalysis and wrote extensively about dream interpretation to uncover hidden desires in unconscious thoughts. And again, to keep to his central message, they were, more often than not, about the need to get his tackle out. This fixation was clearly a cry for help.

For those of you who don’t know about dream interpretation, the idea that dreams can be interpreted to tell the future or even one’s hidden desires has also been around for thousands of years, with sources detailing examples found dating to ancient Babylonia and ancient Egypt. Freud attempted to standarise the symbols and images from dreams and to link them with the subconscious desires they represent. Common symbols and meanings from Freudian dream interpretation include: hats (genitalia), falling (giving in to sexual desire), babies (the desire to have sex to reproduce) and hair (virility (sex drive)). However, in the eyes of evidence based research, Freudian dream interpretation is up there with horoscopes when it comes to credibility.

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Carl Jung. Don’t know about you, but I feel the moustache was a mistake

Carl Jung (1875-1961), was an early follower of Freud who also helped to develop the field of dream analysis. Despite the huge amount of commonality of their ideas, their work eventually diverged after they had what is called in scientific circles as a pissing match, about dream theory. Jung claimed that dreams function to compensate for the parts of the psyche (or the total personality to you and me) that are underdeveloped during your waking hours, and not as a sleep preservation mechanism against physical stimulus. While both believed that dreams contained symbolism, Jung believed that the symbols seen during dreams were less of a puzzle posed by your mind about your unconscious concerns and more about your mind trying to tell you how to re-balance your psyche.

On the basis of a complete lack of evidence, much of Freud’s and Jung’s ideas on dreams is now just an interesting historical footnote in the science of dreams. The real modern-day analysis of dreams begins with Calvin hall (b1953), who developed the cognitive theory of dreams. His work is the first analysis of dreams that is based on quantitative analysis, and not just the sexual whims of a repressed Victorian. After studying thousands of dreams at the various universities he visited, he found that “dreams express conceptions of self, family members, friends, and social environment. They reveal such conceptions as ‘weak’, ‘assertive’, ‘unloved’, ‘domineering’, and ‘hostile’”. Hall believed that dreams are a “dramatization of thoughts” and they reveal actual conceptions and concerns that are not hidden in the unconscious. He believed that dreams were continuous with the waking thoughts, and although they did contain metaphoric elements, he dismissed much of the symbolism, which inherent in Freud’s and Jung’s dream theories.

One of the major contributions of Hall, was that he brought the study of dreams into the (semi-)evidence based light of academic psychology. Unfortunately, more recent and larger studies have discounted his major idea, finding no such continuity between the concerns from the previous day and the dream reports from laboratory awakenings, although this is still very much a disputed topic. Still, at least he got the ball rolling.

More recently, people have tried to apply rational thought to the biological function of dreams. One of the more prominent current theories proposes that dreaming is the result of activation-synthesis. This theory suggests that dreams do not have a meaning and occur as a result of electrical brain impulses that pull random thoughts an imagery from our memories and that the rational stories are created when the brain tried to make sense of the input.

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Anyone remember this beut?

Another theory posits that dreaming may occur as a result of the brain constantly encoding and processing information. This is supported by studies that shows that if a task is completed just prior to sleep, the neural circuits that were involved in that task are replayed during sleep. For instance, a third of participants who played the downhill skiing game Alpine Racer II dreamt about imagery related to the game, such as going into a wall. Interestingly, it was also rare for dreams to exactly mimic the activity.

Originally, dreaming was thought to only occur during rapid-eye-movement (REM) sleep. This is a period in the sleep cycle where brain activity is as fast as when awake. A study published in the Journal of Neuroscience in 2011 found the frequency electrical activity in the brain at different wavebands (alpha, beta, delta, gamma, theta, and mu) as identified by an Electroencephalography (EEG) was altered during the recall of dreams on awakening. They found that participants who exhibited a higher frequency of theta waves in the frontal lobes were more likely to remember their dreams during REM when they awake in the morning. The increased frequency is similar to the behavior of theta waves that occurs during the construction and retrieval of memories, which may be reason why people remember dreams.

Interestingly, it appears that at least some mammals dream as vividly as humans. Michel Jouvet (b1925) conducted several experiments on cats during REM sleep and found that generation of REM depends on the pontine tegmentum which is involved in various motor and sensory functions as well as the control of stages of sleep. When Jouvet caused lesions around the locus coeruleus, which is part of the pontine tegmentum, he found that cats fell asleep as normal, but had less restricted muscle movement during REM sleep, displaying complex behavious, such as what appeared to be the stalking of prey or fighting with another animal. Studies such as these suggest that like humans, other mammals such as cats may also have complex dreams. Such as dreams in which they are plotting your downfall.

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He watches you when you’re sleeping. Ryan CC 2.0

Strong evidence has been uncovered that dreams can also happen during non-REM sleep, especially during the later stages of the sleep cycle and when there are low levels of EEG activity. However, subjects appear to recall these dreams much less frequently if allowed to wake naturally, possibly as a result of the lack of a reliance on high theta frequency, which is associated with the formation and recall of memories that happens with REM dream recall. The dreams that occur in non-REM sleep were also found to be different to dreams during REM, being more thought-like and involving the thalamo-cortical network, in comparison the more abstract REM dreams.

A recently study published in Nature Neuroscience revealed that dreaming occurs during a period of low frequency activity in the “posterior cortical hot zone” which includes visual areas as well as areas that are involved in integrating the senses. More importantly, dreaming was found to occur when the frequency dropped, regardless whether it was during REM or non-REM sleep. These findings were so robust, that they were able to predict whether the participants were dreaming 87% of the time.

This could mean that the low-frequency activity in the cortical hot zone is a default state of your mind uses to prevent the recall of dreams, or what researchers call “experiences”. When the low frequency is turned off, our brains feel free to create new experiences or dreams. Whether that be winning the world cup, saving the world from an invasion of Orks while on the back of your unicorn steed. Regardless of your dream, areas of your brain associated with the topic become active during your dreams state. For instance, dreaming of saving the realm from Orkish would light up the region of your brain which recalls living in your Mums basement until you were 35.

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You may laugh now, but they’re coming for you. Walter Meyles CC 2.0

Intriguingly, as dreaming is considered a conscious state, the authors of this study also speculate that this region may be the region that has a core roll in control of your consciousness. In line with this. It has also been suggested that given a sample of 75-100 dreams, a psychological portrait of a person can be made that would be as individual as a fingerprint.

While the verdict is still out as to whether dreams have a function, it now seems clear that they are not simply just random images as they also correlate with age and gender. For instance, the diversity of dream themes was found to reduce with age, possibly as a result of the loss of episodic and autobiographical memory (memories for episodes which are personally significant and emotional in nature) are reduced with age.

What is clear, is that despite over a decade of speculation, study, and the ravings of a randy psychoanalyst, we are only now beginning to see tantalizing evidence of their origins.

A couple of other interesting dream facts: 

  1. Colourblind people dream in the same shades as they see the world
  2. There is some evidence to suggest that dreams can be controlled (lucid dreams), although the evidence is scarce and one of the scientists who ran the study calls himself a dream sailor, which I cant image helps his case…
  3. People that look for a meaning in their dreams are more likely to believe in them as ‘meaningful’ if they conform to their waking beliefs
  4. Night terrors sound… well… terrifying

Featured Image: Michael Carian CC BY-SA 2.0


A bit thanks to N at the Opinionated Head and TizziMatic for the idea for this post. Be sure to check out their stuff and spread the love!

Any questions that have have you vexed? Never figured out how something in biology works? Drop me a line and I’ll see if I can set that right.

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