By Roshnie Soekhoe
Can you still remember your dream from last night? If so, chances are high that it included a series of fictive events full of emotions, feelings, and images that played in your head like a story. Sometimes, such dreams seem to have no clear narrative or merely appear to be a set of random and bizarre moments put together. Are such dreams truly haphazard though? Why do we dream about the things that we dream about? And what are dreams exactly anyway? For such questions to be answered, let us first look at what the science behind dreams has uncovered.
The Discovery of REM Sleep
Oneirology, the scientific study of dreams, first originated in the 1950s when an American research team started to rigorously study the physiology of sleep and the connection of rapid eye movement to dreaming. This team, consisting of physiologist Nathaniel Kleitman and at that time graduate students Eugene Aserinksy and William Charles Dement, proposed the idea of regular sleep cycles and stages during human sleep. In contemporary society, we know of the existence of four or five sleep stages in one sleep cycle. One cycle lasts approximately ninety minutes and goes through the non-rapid eye movement (NREM) stages N1, N2, and N3, which is sometimes merged with N4, and through the rapid eye movement (REM) stage. At the time of discovery though, this was a major finding for the neuroscientific field of dreams. The realization of REM sleep in particular provided a large foundation for further research in this area. The scientists noticed that some marking characteristics of REM sleep are the immobilization of the body (muscle atonia), rapid eye movements, and more frequent dream occurrences. Presumably, the former two effects would prevent the dreamer from physically acting out their dream while still allowing them to scan the dream’s content with their eyes. Furthermore, respiration also increases and certain parts of the brain become significantly more active according to electroencephalogram (EEG) tests that monitor the electrical activity in the brain. The high-frequency and low amplitude electrical signals that are emitted in this stage seem to have remarkable similarities with the electrical signals and corresponding brain waves emitted during wakefulness. This means that activity in the brain during REM sleep closely resembles the brain activity that is perceived when a person is normally awake.
Functions of the Brain & Dream Characteristics
Later on, researchers in the 1990s were able to further delineate between an increased or decreased activity in the brain by virtue of a newfound neuroimaging approach called positron emission tomography (PET). The application of this technique yielded a clear picture of which parts of the brain had an increased and decreased activity during the stages of both REM sleep and wakefulness, subsequently facilitating comparison between those two. The results were later also used to explain some of the most typical characteristics of dreams, for instance:
- The occipital cortex on neuroimaging results is seen to be closely related to visual imagery with the eyes closed. Increased activity in that area during REM sleep could thus explain the visual images reportedly seen while dreaming.
- Hyperactivity in the hippocampus could explain the appearance of familiar scenes/settings or characters in dreams, as the hippocampus plays a major role in learning and memory retrieval.
- The amygdala’s activity during REM sleep could explain the emotional experience of dreams since the amygdala is responsible for processing emotions.
- A lack of activity in the lateral prefrontal cortex could explain the inconsistency and bizarreness of dreams as well as the dreamer’s lack of control over their content and disorientation in time and space, as this part of the brain is correlated with metacognitive processes such as working memory, reasoning, and planning.
- Lastly, hypoactivity in the right inferior parietal cortex could explain the ability to participate in both first- and third-person perspectives, because this region is mostly concerned with egocentric versus allocentric representation.
Non-REM and REM Sleep
While much dream research has centered itself around REM sleep and its findings can greatly explain dream phenomena, this is not the only sleep stage in which dreams can manifest themselves. Although more individuals initially reported to have dreamed after awakening from REM sleep, participants also recall having had dreams after NREM sleep. However, the fact that dreams can take place during both REM and NREM sleep does not mean that dreams possess equal phenomenological characteristics. In reality, they differ quite starkly.
REM dreams can be experienced in a much more sensational and vivid manner than NREM dreams. Dreamers can perceive their dreams through visual and auditory perception and experience ‘physical’ interaction with their dream environment through motoric action, such as moving oneself from one place to another and self-motion. REM dreams further follow strange yet elaborately rich narratives throughout which dreamers can feel more enhanced levels of emotions, such as joy and surprise as well as fear and anxiety. Contradictorily, NREM sleep activates and deactivates far less parts of the brain than REM sleep and also uses a different type of memory, which could explain the difference in dream contents. NREM sleep namely uses declarative memory while REM sleep uses implicit memory. This means that during NREM sleep you would be more likely to dream about events or things that you consciously tried to remember in your everyday life, such as the study material of a math test. In REM dreaming, things that you unconsciously learned would be quicker to appear, such as the face of a character or an object you don’t even remember seeing. This may explain why NREM dreams have often been reported to be shorter and fragmented, less sensational, less emotional, more hallucinatory, and reflective of current concerns.
The Role of Dreams
Dreaming can thus be considered to happen along a continuum stretching across the stages of NREM and REM sleep rather than an explicit phenomenon confined to one particular stage. We furthermore established that dreaming can activate or deactivate certain parts of the brain, display a wide range of images and events, and bring about intensely felt emotions. Now we know what happens and how, the question then becomes why. Why do we see the things we see in our dreams? Do dreams serve a particular function or role? In the neuroscientific and psychological field of dream research, several theories have risen as to why we dream and if there is a specific meaning to them.
One of the most well-known theories is Freud’s theory postulated by the neurologist Sigmund Freud. In the early twentieth century, Freud proposed the notion of psychoanalysis and the concept of the unconscious. He asserted that this most inner part of the mind exists of beliefs, thoughts, emotions, and desires that might be subliminal but nevertheless significantly influential on the conscious mind and an individual’s behavior. In his book (The Interpretation of Dreams), he suggested that dreams reflect such unconscious feelings through manifest and latent content. The former relates to the actual images exhibited in dreams and the latter relates to the hidden meaning behind those dreams. According to Freud, the latent content is concealed by the manifest content in a disorienting way before it can reach the awareness of the conscious mind. The latent content may include repressed feelings or unacceptable thoughts, such as traumatic experiences, secret desires, or socially unacceptable ways of thinking. Such content could cause distress to the person and wake them from their sleep if they were outright displayed in each dream. Uncovering the hidden content of dreams could be done through free association, an essential technique in psychoanalytic therapy. Analysts encouraged individuals to discuss the manifest content of their dreams and speak and express themselves freely when trying to interpret the meaning behind them. With each session the patient would eventually gain insight into their own unconscious feelings and release themselves from the oppression of the unconscious mind. Thus, as stated by Freud’s theory, dreams provide a pathway to the unconscious. Even though many of Freud’s assertions have been labeled as unscientific by neuroscientists, research has acknowledged that suppression of thoughts often leads to their return in dreams, and this is also known as the dream rebound effect.
Another mainstream theory that on the other hand did receive much support from neuroscientists is memory consolidation. Results of previous studies show that whenever we learn or practice a complex task, the same brain activity that occurs during the learning process repeats itself in post-training dreams. The experience gets re-created and subsequently enhances the memory. Experimental tests illustrated that individuals who took post-learning naps performed better on the task in question than those who did not. Although dreams do not always include learning material or rehearsals in its content, many investigated dream reports show that dreams relate to at least one recent memory. As such, these lines of evidence point toward the possibility of dreams being conducive to reinforcing newly acquired memories and information.
Yet, the brain does not equally enhance all past memories. Instead, it selectively emphasizes a particular piece of information that is helpful to a person’s future. Further examinations demonstrated that a dream only enhanced memory and included study material when a participant was expected to be tested on that subject the following morning. Emotional memories or memories that one expects to be rewarded for are usually enhanced in sleep. Dreams can thus serve as preparation tools for future scenarios in which remembering a specific memory can be helpful. However, dreams can also construct completely different situations that are not related to any past memory or information. Have you ever had a dream in which you either fell off a building, showed up naked in public, got chased by a stranger, or failed a very important exam? The threat simulation theory proposed by psychologist Antti Revonsuo suggests that being in such threatening or emotionally intense scenarios can help us to be better prepared for them in the future, whether that’s making sure to avoid it or knowing how to handle it. Dreams thus also offer us a space of impunity in which we can safely practice such situations without actually being harmed and hone our instinctive survival skills.
This list of theories is not exhaustive and there are many other divergent theories out there attempting to explain the meaning behind dreams. On the one hand, the activation-synthesis theory of neurologist Alan Hobson proposes that dreams have no function at all and that the brain is simply trying to find some meaning and coherence in the internal stimuli during REM sleep. On the other hand, theories that do claim that there is a meaning behind dreams vary widely: dreams may help to process our emotions, declutter our minds, or perhaps even promote creative thinking.
This goes to show that there’s still uncertainty revolving around the true meaning of dreams. Whether it’s your unconsciousness furtively attempting contact through your dreams, your memory being recalled, or your brain throwing you in a deadly situation to kindly prepare you for future disaster; the true meaning of dreams might not be exclusive to one theoretic perspective relating to either cognitive neuroscience or psychoanalysis. Much is still unknown, so it could just as well be a mixture of all of them or, on the opposite hand, none of them. Since both neuroscience and psychoanalysis agree that dreams are very personal and relate to meaningful issues, perhaps it is you who can decipher the special meaning behind your very own dreams.If you’d like to read more about the theory of Sigmund Freud, this is a direct download link to his book : ‘The Interpretation of Dreams’ (the standard edition).
Edited by Joanna Sowińska, artwork by Teresa Valle