Discover the neuroscience of dreaming

The phenomenon of dreams has fascinated philosophers and scientists for thousands of years, yet the question still lingers – what happens during dream sleep and why exactly do we dream? Here we explore the neuroscience and psychological theories of dreaming.

Dreaming is perhaps the greatest shared “unshared” human experience. From disjointed anecdotes and blissful experiences one may be disappointed to awaken from, to fear-inducing nightmares and complex real-life-related sequences that play out in distorted dreamscapes,
humans experience a vast number of dreams throughout their lives. Yet since these dream experiences manifest exclusively in an individual’s mind and are highly subjective, often fragmented and non-linear narratives which cannot be shared other than by personal waking recount, it is impossible to ever truly share the experience of dreams.

So what ties all dreams together? What role do dreams really have in our lives? Why does the brain crave dreaming? What is happening at a neurological level when the mind rolls the dream projector each night? Contemporary neuroscience and psychology is elucidating more concrete answers to these seemingly elusive questions.

A brief history of dreaming

A common thread that runs through many ancient societies is the belief that dreams were a source of divination (a way to predict the future) or that they could reveal the meaning of the past and present, including seriously guiding real-life situations.

Interpreting dreams was regarded as an art form and science in the ancient cultures of Mesopotamia, Egypt, Greece and Rome that required intelligence and often a spiritual connection.

In these past civilisations, meanings and messages in dreams were often believed to be encoded in symbolism. In ancient Greece, a method known as incubation was practised, where the dreamer could sleep in a sacred place, such as a temple precinct, with the expectation to receive divine guidance through a dream in relation to a specific real-life problem or situation.

This fascination with dreaming has transcended time. Throughout history, the motif of dreaming has continually appeared in science, spirituality, arts and literature as a phenomenon imbued with a powerful ability to interplay with its binary of reality. In 1899, Sigmund Freud published The Interpretation of Dreams, in which he introduced his theory of a dynamic unconsciousness in relation to the mechanisms of dreaming.

According to Freud, dreams follow their own kind of logic for which he coined the term “dream-work”, and comprise various components, such as external-world stimuli, stored subjective experiences, natural stimuli within the body and mental activities that occur while asleep. Freud believed the interpretation of dreams to be the “royal road” to a knowledge of the unconscious activities of the mind and therefore a valuable asset to psychoanalytic practice. While Freud’s work remains significant to this day, he was aware of the scientific limitations of his time, predicting that “deeper research will one day trace the path further and discover an organic basis for the mental event.”

The phenomenon of dreaming

Fast-forward to the more recent years of the 21st century and the rigorous study into the phenomenon of dreaming has finally fulfilled Freud’s prediction. So what facts and theories does contemporary science present about dreaming and the neurological function of the brain while in a dream state?

By its basic science-founded definition, a dream is a succession of images, ideas, emotions and sensations that occur involuntarily in the mind during certain stages of sleep. Quantifiable data suggests that all humans, whether they remember their dreams or not, spend approximately two hours dreaming every night, during which multiple dreams are experienced. Each dream lasts around five to 20 minutes, though longer or shorter dreams may also happen. The nature of dreams spans from intensive, emotional, moving and vivid to the other end of the spectrum, where they may be confusing, vague, fleeting or dull. Some dreams will take shape through a clear narrative, while others appear to be fragmented or make absolutely no sense. The feelings that dreams can evoke cover the rollercoaster of human emotion, from pleasurable and joyful, to saddening and terrifying.

Dreaming is an extraordinary experience when compared to the non-dreaming brain. As neuroscience professor and sleep expert Matthew Walker describes it, entering a dream state can be likened to experiencing a controlled, momentary psychosis. Analogically, you hallucinate (see things not really there), become delusional (believe things that couldn’t be possibly true), become disorientated (suffer from confusion of time and place), may undergo bipolar-like mood swings (through wildly fluctuating emotions in a singular dream narrative), and finally experience amnesia (you awaken from your dream only to forget some — if not all — of it). When you consider dreams like this, there is no question as to why they have fascinated humans over the ages.

Neurological components of dreaming

All stages of sleep have unique and separate functions; you need them all. As Walker points out, “Evolution has taken a long time to get this blueprint right.” Most dreaming occurs in the rapid eye movement (REM) stage of sleep; however, it has also been found to happen in non-REM (NREM) sleep. During REM sleep — the deepest stage of sleep, which takes place mostly during the last third of the night — your eyes
move around in a range of directions at a fast pace, yet send no visual information to the brain. This does not occur when you are in the NREM stage of sleep cycles.

REM sleep has several other unique markers, which point towards the importance of dreaming. The stages of NREM sleep preceding REM bring on gradual muscle relaxation. By the time you get to the REM stage, the mind paralyses most muscles in the body in a condition known as atonia, so that it can essentially dream uninterrupted. This temporary paralysis keeps legs and arms from reacting and flailing in response to dream content.

Furthermore, when you go into REM sleep your brain undergoes changes in its activity centres. Certain parts of the brain become 30 per cent more active compared to when you’re awake. This includes increases in the visual, motor, emotional and memory centres. Conversely, the
prefrontal cortex — responsible for rational and logical thought processes — is shut off. Walker figuratively describes entering into REM like waving goodbye to the logical part of your brain; it’s as if the usual “guards” have left the building and the mind can now run wild and free.

This means that you surrender your waking control as you go into a dream state, ultimately relinquishing a large portion of free will and becoming a passenger to the narrative.

During dream sleep, the chemistry of the brain is also radically different. Noradrenalin, the main neurotransmitter of the sympathetic nerves in the cardiovascular system, plummets to its lowest levels. Meanwhile acetylcholine, the chief neurotransmitter of the parasympathetic nervous system, amps up, augmenting the input and output of information flow to the memory centres of the brain. Your mind and body are existing in a “rest and digest” state while dreaming, and this brain chemistry presides over your systems even if you are dreaming a frightening nightmare. It isn’t until you wake up that you will get spikes of stress-related hormones and shift into a sympathetic “fight or flight” state.

The link between dreaming and waking consciousness

While striking neurophysiological differences exist between sleeping, dreaming and being awake, examining the similarities between
how the brain works (in terms of activity and organisation) during waking and dreaming realities can help to gain further insight into the phenomenology of dreaming.

Have you ever awoken from a dream to be shocked that you were only dreaming because it seemed so real? Conscious experiences in sleep can be strikingly similar to the dreamscape (or inner world of your dream) can be to wakeful worlds. Indeed, dreamscapes and narratives
are visually saturated with colours and movement, and are populated by typical categories that inform wakefulness, such as places, people, objects and animals. Just as in waking life, dreams are sensory: you see, hear and feel your dreams, rather than dreams appearing as abstract thoughts.

Dreams are not randomly subjective in the narrative content that your brain creates; they reflect your individual personality, interests and experiences in much the same way as these elements condition mental activity during wakefulness. Formal dream content analysis backs this up, revealing, as Nir and Tononi state, “that mood, imaginativeness, individuals of interest, and predominant concerns are correlated between our waking and dreaming selves.”

The functions of dreaming

Some have suggested that dreaming is not actually the primary function of REM sleep but rather is a by-product of it. After understanding the above complexities and efforts that the brain goes to in order to put you into and keep you in a dream state, this explanation seems unsatisfying and unlikely. As Walker poses, why would the brain create the dream experience, subjecting you to two hours of “virtual reality” every night, if it doesn’t serve a significant purpose? Dreaming also uses energy, and when we burn calories it usually has an important function. This is because from an evolutionary perspective, energy is precious.

Looking at the biological evolution of REM sleep and dreaming, emotion theorist Jaak Panksepp believes that it allows for ancient emotional impulses to be integrated with the evolved cognitive skills of the more recent human brain’s waking systems. This could help explain some of the prominent dream theory functions of REM sleep, which include memory consolidation, enhanced learning and a way to gain practice in confronting potential situations or dangers.

Freud’s theory emphasises dream content and views this as a path into the dreamer’s unconscious reservoir of feelings, thoughts, urges and memories existing outside conscious awareness.

While acknowledging that these factors may come into play in dreams, contemporary theorists have varying ideas about the role of dreaming that supersedes the focus being primarily on the individual dreamer’s psyche.

Allan Hobson’s Activation-Input- Modulation (AIM) model of dreaming asserts that dreams facilitate “protoconsciousness”, a virtual reality
model which provides a creative function wherein the brain is preparing itself for integrative functions, including learning and secondary consciousness. However, this theory suggests that dreams reflect the dreamer’s physiological and psychological activities such as memory
consolidation, emotion regulation and reception of external stimuli, rather than being independently functional.

Clinical psychologist Dr Shelby Harris, who specialises in behavioural sleep medicine, views REM sleep as your brain’s “filing cabinet” where emotional and cognitive sorting, processing and organising is taking place. In this way, dreams may serve the purpose of your brain trying to make sense or tell you something about what is going on in your life, or they could take form as symbolic projections of psychological states. For example, at times of your life when you are stressed you may have a recurring dream reflecting those emotions, such as being unable to remember the combination to your high school locker or running late for a work meeting.

Wakefulness and dream content have clear parallels. Research on people going through a divorce who were depressed found that they dreamed differently to those who are not depressed, rating their dreams as more unpleasant. Fascinatingly, the study showed that those whose dream content included their ex-spouse were more likely to have recovered from their depression a year later, versus those who did not dream of their ex-spouse. While more research is needed, this information suggests that you are more likely to incorporate internal and external factors into your dreams — therefore your dreams may reflect current life situations and waking emotional states as a way to better process and manage them.

A portal of creativity

One desirable function that dreaming has served for many is to spark creative inspiration then brought from the dream realm into waking fruition. There are plenty of famous examples of this throughout history. Studies that have confirmed the correlation between dream sleep and creativity, coupled with anecdotes such as these, affirm that dream states are a powerful tool for birthing non-logical, unique ideas and concepts.

Can you make sense of your dreams?

When you wake up from a dream and it’s fresh in your mind, the logical part of your brain suspended during REM sleep jumps in
and tries to package up your dream content to make sense of it. However, dreams cannot be so easily made sensible or “decoded”.
This is similar to the quest to find one logical answer to why humans dream. Many contemporary experts believe that you dream due to a combination of the reasons discussed above, rather than accepting any singular theory. Regardless, most agree that REM sleep and dreaming are essential to mental, emotional and physical wellbeing.

To become more aware of your dreams, a good place to begin is by using a dream journal to write your dreams in (or what you can remember of them) as soon as you wake up. You can then look for common themes that arise and how this may relate to your life. According to psychologist Athena Laz, who works closely with all forms of dreaming with her clients, the result of keeping a dream journal is that “You are in direct communion with your inner being, and a larger state of consciousness … through that direct relationship, you receive incredible benefits by way of creative solutions, problem solving and guidance.” By connecting with your dream states, you can cultivate an inner dialogue between sleeping and waking hours that may help make sense of the unseen, as well as the world around you, by tapping into your subconscious landscape.

So while there may not be a definitive answer as to exactly why we dream, the psychology and neuroscience of dreaming affirm that its function is important for the human experience, existing in a two-way discourse between the worlds and consciousness of sleep and awake.
Perhaps trusting in that is enough; waking sense need not be made of dreamland “hallucinations”; rather, that dreams be celebrated for the wildly bizarre alternative realities they take us to when we drift off to sleep each night.