For this weeks blog we hand over to our very own Steering Group and Evaluation Lead for the Lincolnshire Sleep Hub Caroline Horton Professor of Sleep and Cognition, Lincoln Bishop University; Co-Director of the Lincoln Sleep Research Centre; Trustee and Treasurer of British Sleep Society; Director of the DrEAMSLab.
Dreaming is a universal phenomenon though it can be quite divisive, as some people seem to relish in sharing and thinking about their dreams, whilst some others hold strong views that dreams are hocus-pocus or useless. As a dream scientist, I try to study dreaming as systematically as possible, without interpretation or bias.
The outcomes have provided some fascinating insights into our mental images and emotions that captivate our consciousness during sleep.
What are dreams?
Dreaming occurs during sleep, and sleep is a fundamental pillar of health and wellbeing. The Oxford English Dictionary defines a dream as: A series of images, thoughts, and emotions, often with a story-like quality, generated by mental activity during sleep. However, as sleep scientists we know that our experiences of dreaming rely entirely upon the extent to which we can remember these thoughts and experiences that occur during sleep. Sometimes these are brief and fleeting. Sometimes they are highly emotional, exciting or frightening, detailed, and vivid. In all cases, our understanding of the science of dreaming is entirely mediated by our recall processes. Many things can impact upon those recall processes, such as how quickly we wake up and attend to our waking lives, how long we have slept for, how stressed we are, and how emotional or salient the dream is.
In 1953, sleep researchers Eugene Aserinsky and Nathaniel Kleitman observed that periods of rapid eye movements during sleep were associated with brain activity patterns similar to wakefulness, and also when people were awakened from these periods, they often reported dreaming. This led to an assumption that dreaming occurred only during certain stages of sleep. Now, we have a much more detailed and nuanced understanding of the science of dreaming: dreams can be reported from all sleep stages (we often struggle to recall dreams spontaneously from very deep sleep because we want to get back to sleep again!) and we appreciate that, although all healthy humans dream, many people routinely do not recall their dreams. This is entirely normal and perhaps even functional, to prevent us from confusing activities from our dream worlds with our waking lives.
What are the key features of dreaming?
There are several key characteristics of dreaming that many of us will recognise: dreams can be emotional, particularly negative, bizarre, sometimes realistic, and can leave us with a sense of wonder upon waking. Although we can often recognise or comprehend some elements that featured within a dream, they can also appear as extremely unusual or inexplicable. Dream researcher Calvin Yu has categorised common dream themes, noting that many dreams feature activities or characters that are highly similar. The most common dream theme is being chased, which can appear in many forms. This presents an interesting conflict in dream science: how can dreams simultaneously comprise elements that we are so familiar with, yet at the same time create new compositions and experiences?
One way we can try to make sense of dreaming being universal yet personal is by trying to characterise the individual sources of dreams. Historically, theories of dreaming have included influences from the divine, the unconscious, and, more recently, from random brain activation, implying that dreams are entirely meaningless and unmotivated. Contemporary dream scholars have applied scientific rigour to the study of dreams and now recognise the complex neurocognitive environment in which dreams occur, that transitions not only from wake to sleep, but also across different sleep stages. Within that context, autobiographical memories; or memories for our own personal experiences, form the building blocks of dreams. Autobiographical memories can comprise some experience-based information as well as knowledge about our own lives. Furthermore, they can include information about experiences that can be constructed, or that changes over time. Importantly, dreams do not replay personal experiences from our waking lives directly, but instead incorporate elements of our experiences either indirectly, or in an altered way. For instance, we may dream tonight about a visit to the supermarket that we visited on the way home to pick up some things for dinner, but in that dream we may be eating a meal there, talking to Harry Potter, or flying on a broomstick with the ingredients under our arm. In this way we may recognise elements from our waking lives, but those elements have been merged with other aspects of our experiences and emotions, to create a new, seemingly bizarre experience.
Emotional dreams
Dreams clearly reflect our emotions, and we may have awareness of that from our own lives. Whilst memories are the building blocks of dreams, emotions often guide the activation of specific memories and can strongly influence the recallability of them insofar as we have enhanced recall for emotional experiences both from waking life as well as from sleep.
Dreams can be both positive as well as negative, and, once we control for any recall biases, are slightly more emotional than our waking life experiences. Memories that feature in dreams tend to be more emotional and salient than those we do not dream about, and dreams that we consider to be important or meaningful are often highly emotionally charged. We dream of our current concerns as well as upcoming events, such as hospital visits or a pressing work task. In this way, the emotional tone of a dream often reflects the emotional tone of our current waking life experiences, even if the specific activities within a dream do not.
Nightmares
Nightmares are negative dreams that are so arousing they wake us up and these are prime examples of these reflections of our emotions from the day. Nightmares are common in that almost all people will experience nightmares at some point in their lives, and they are particularly frequent during childhood, likely at a time of developing independence and learning about real threats in the world. Nightmares can also feature in adulthood and, if frequent and disturbing, often co-occur with other mental health challenges such as anxiety and trauma processing. In contrast, grief dreams can be as positive as they are negative, and all can reflect emotion processing. Until recently it has been believed that such processing as well as emotion regulation occurred primarily during rapid-eye movement (REM) sleep, but evidence indicates that all stages of sleep are important for emotion regulation, with disruption to deep as well as REM sleep leading to heightened anxiety responses.
Despite all this, repeated negative or anxiety dreams could imply either that our sleep is insufficient for our emotion-processing needs, and/or that we have an overwhelming amount of emotion to process in the day, that perhaps requires some additional reflection or support. Paying attention to our dream characteristics, along with our wider sleep and mental health, can be not only enjoyable, but also indicative of general health.
Negative dreams may be unpleasant and we may wonder why our minds create such unpleasant thoughts. We are likely processing emotions in a safe space, both physically and psychologically, helping us to be well-regulated and rested for the day ahead. The body of evidence supporting the idea that sleep is crucial for processing and regulating emotions is vast, however, it is impossible to disentangle the effects of dreams on emotion processing from these effects of sleep. We hope that, in time, we may be able to detect the presence of dreaming that does not rely solely on one’s recall processes, as that may allow for more sophisticated experiments comparing periods of sleep with dreams to those without on outcomes such as emotion regulation, memory consolidation, and integration of salient experiences.
In conclusion, our dream worlds can be fascinating and terrifying in equal measure. Although we can’t yet determine their precise function or functions, it is likely that dreaming is a conscious manifestation of emotion regulation and memory consolidation processes that occur during sleep. Remembering those experiences may afford us the opportunity to reflect on the salience of personal events, whilst also providing information about our sleep health.