A World of Pure Imagination: The Neuroscience of Lucid Dreaming

Clem Doucette and Gerasimos Copoulos

Illustrations by: Sophie Sieckmann

Is this the Real Life… Is this Just Fantasy? 

During a visit to New York City several years ago, I took a walk through the Lower East Side. As I gazed up at the beautiful Victorian buildings lining the narrow streets, I felt as if I were being drawn back into some forgotten era. Across the street, I spied a tiny, old-fashioned Italian market and decided to go inside. I passed by the store clerk, headed to the back wall of the shop, and passed through a small door. As I walked through, the modern cars and taxis of Delancey Street were replaced with horses and buggies; men wearing flat caps and women donning long dresses and bonnets rushed down the street shouting things in various languages, while a group of children played baseball in a back alley. At this point, you might be thinking that I had experienced some kind of wild delusion or hallucination. In reality, what I am describing are the events of a particularly vivid lucid dream.

Have you ever been fully aware that you were dreaming? If so, then you have experienced a lucid dream. When a dreamer enters a lucid state, they can often control, or “rewrite,” the environments, events, characters, and even physics of their dream. Anything is possible in a lucid dream; you can fly between tall buildings, fight off hordes of zombies, or live out your wildest fantasies. In many cases, the experiences of your lucid dreams are limited only by your own imagination. Once described by Freud as the “royal road to the unconscious,” dreams have both fascinated and baffled philosophers and scientists for millennia. While lucid dreaming may seem like a miraculous or otherworldly occurrence, the neurological and psychological underpinnings of these dreams are the focus of a growing body of research. Though the precise neural correlates underlying lucid dreaming remain uncertain, lucid dreaming holds immense therapeutic potential.

The Stuff of Dreams: The Science Behind Dreaming and REM Sleep

In order to understand the mechanisms behind lucid dreaming, let's first discuss how sleeping and dreaming generally work. Sleep occurs in four distinct stages. The first three are the non-rapid eye movement (nREM) stages, and the fourth stage of sleep is rapid eye movement (REM) sleep [2]. The first of the three nREM stages, N1, is the lightest stage of sleep and occurs shortly after your head hits the pillow, typically lasting for only 1-5 minutes. The second, N2, is a somewhat deeper stage of sleep, lasting for roughly 25 minutes. During N2, your heart rate and body temperature begin to drop. N3, the last of the three nREM stages, is the deepest; if you wake up during this period, you may experience a period of mental fogginess. After remaining in nREM sleep for roughly 90 minutes, you pass into the fourth stage, referred to as rapid eye movement (REM) sleep. The vast majority of our dreams occur during REM sleep [2]. For a while, scientists could not come to a consensus on why dreaming occurs during the REM stage, or the function of REM in general. However, in the last decade, several hypotheses have emerged that shed light on the functions of REM sleep.

One hypothesis suggests that REM plays a role in the development of motor learning and memory, since newborn mammals spend a lot of time in active sleep, an early form of REM that is crucial to that development [3]. During active sleep, young mammals are often observed producing a flurry of muscle twitches and vocalizations as evidence of ongoing motor learning. Mammal species born with less developed motor and learning memory, like humans and most primates, spend relatively more time in active sleep than mammal species born with more developed motor skills and memory, like horses [3]. The excess time that some mammals spend in REM or active sleep may suggest REM fosters the development of the systems underlying motor learning and memory [4, 3]. A better understanding of REM can improve our understanding of lucid dreaming. When we lucid dream during REM, we enter a hybrid state of sleep and wakefulness [1]. Even though the exact purpose of REM sleep isn’t well understood, REM and even lucid dreams are easily identifiable via imaging techniques [6]. 

Imaging a Dream: The Electrophysiology of Lucid Dreaming

Various technologies can be used to differentiate between standard REM sleep and a lucid dreaming state; but, some of the most useful are imaging technologies. Imaging the brain during a lucid dream allows for further study of the mechanisms behind lucid dreaming [1]. One common imaging technique uses a machine that reads different electrical signals produced in the brain: an electroencephalogram (EEG) [7]. When a sleeping person’s brain is examined with this technology, the EEG reading displays different kinds of waves depending on the sleep stage [6]. REM sleep waves, for example, are short and frequent [6]. As lucid dreaming involves a different mental state than a normal REM dream, lucid dreaming produces a different EEG reading than standard REM sleep [8]. There are visible differences in the EEG readings observed between lucid dreaming and either REM or wakefulness. However, EEGs can detect interference from eye movements during REM, casting doubt on if these EEG readings actually show lucid dreaming.

Verifying the EEG readings with fMRI, another method of brain imaging, provides further evidence that lucid dreaming is distinct from standard REM. Functional MRI imaging records activity in various brain regions over a period of time and then displays it visually on a model of the brain [10]. Traditionally, dreams are closely associated with REM; but, one can also lucid dream during non-REM sleep [13]. When using fMRI alongside the EEG to examine people lucid dreaming in both REM and nREM, REM lucid dreams appear distinct from nREM lucid dreams [14]. Some wave patterns apply only to REM or nREM lucid dreams. More specifically, lucid dreaming appears differently on the EEG and fMRI depending on what sleep stage one enters the lucid dream from, indicating more differences in wave patterns among lucid dreams than previously thought [14]. 

If different varieties of lucid dreams exist between REM and nREM, there may not be a single wave pattern that shows lucidity in any sleep stage [14]. The question remains as to why lucid dreams look so different in the EEG depending on if they occur during REM or nREM. After all, aren’t they all lucid dreams [14]? Fortunately, there is one explanation readily available, though it raises as many questions as it does answers: different methods of becoming lucid lead to different wave patterns [15]. nREM and standard REM lucid dreams involve becoming lucid at different times and through different means, explaining the discrepancy between these two kinds of lucid dreams in the EEG [13]. 

The Lasting Effects of Lucid Dreaming

The EEG can give us fascinating insight into a lucid dreamer’s brain as they dream; but, it is impossible to deduce the long-term effects of lucid dreaming from an EEG reading [7]. One possible way to examine these effects is to look at the brain structure of lucid dreamers. It turns out that lucid dreaming correlates with a number of differences in the brain, such as in grey matter volume and connectivity [16, 17]. Grey matter is brain tissue that contains the most neural connections, linking it to overall cognitive performance, memory, and decision-making [18]. Grey matter volume is significantly higher in frequent lucid dreamers; this volume difference may provide insight as to how some people are better able to frequently lucid dream than others. [17]. Lucid dreamers also exhibit increased connectivity between brain regions that modulate attention and sensory processing [16]. The increased grey matter volume and connectivity in frequent lucid dreamers suggest that lucid dreaming has a measurable long-term effect on the brain’s structure [16, 17]. However, whether lucid dreaming is innate or learned may affect EEG recordings or observed brain anatomy [1]. More reliable lucid dreaming induction techniques must be developed before researchers can isolate the neurological differences between innate and learned lucid dreamers.

Entering the Lucid State: How You Can Induce a Lucid Dream

The act of induction, or causing a lucid dream to happen, is often hit-or-miss. Today, no consistent way to induce lucid dreaming exists, which has made conducting research on the subject matter difficult [13]. The mnemonic induction of lucid dreams, or MILD, was pioneered by lucid dreaming research specialist Stephen LaBerge and is currently considered the most reliable means of lucid dream induction [19]. Prospective lucid dreamers perform the MILD technique during a brief period that occurs roughly five hours after falling asleep; while awake, individuals can repeat phrases such as, “next time I’m dreaming, I’ll remember that I’m dreaming” or, “I will have a lucid dream” before returning to sleep. People who practice the MILD technique consistently for two weeks experience lucid dreaming approximately one out of every six nights [19]. Therefore, while MILD is currently the most reliable induction method available, it is by no means a highly consistent way of inducing lucid dreaming [19]. However, other methods to induce lucid dreaming outside of the MILD technique exist [13]. These methods, such as the use of pharmaceuticals and electrical stimulation, seek to induce lucidity through more direct interventions and may provide greater insight into how lucid dreaming works.

In the sci-fi film Inception, Yusuf, a chemist, concocts a mysterious sedative that is powerful enough to induce three levels of lucid dreaming: a dream within a dream within a dream. For now, the development of such a substance is far outside the realm of current possibilities, since we currently know only of substances which increase the odds of a lucid dream occurring [1]. Pharmacological, or drug-based, induction of lucid dreaming may be necessary if lucid dreaming is to be used in clinical or research settings [1]. One drug that has shown great promise in the induction of lucid dreams is galantamine, especially when used alongside the MILD technique and other traditional induction techniques [16, 20]. Galantamine works by inhibiting acetylcholinesterase (AChE), an enzyme responsible for breaking down acetylcholine (ACh). ACh is a neurotransmitter in the brain that impacts REM sleep [21, 22, 23]. Galantamine administration increases excitation in brain regions typically inactive during REM sleep, enhancing cognitive performance and making it easier to lucid dream [16, 1]. The success of galantamine has spurred similar investigations into other substances that increase acetylcholine levels [1]. One of these is an acetylcholine precursor, called α-GPC, which is available as a prescription-free drug [24]. A precursor refers to a molecule that the body uses in a chemical reaction to produce another molecule; in this case, the product is acetylcholine. However, α-GPC has had no success in the induction of lucid dreaming. No other drugs that reliably induce lucid dreaming have been found [1]. Isolating additional drugs that can induce lucid dreaming is warranted to advance lucid dreaming research and therapy. 

Current induction methods merely increase the odds of a lucid dream occurring and rely largely on self-induction [19, 24]. What if there were a direct, consistent way for researchers to cause a dreaming person to become lucid? One exciting possibility involves electrically stimulating the brain [1]. Unlike other methods of induction, electrical stimulation could not only provide the most reliable route to having a lucid dream, but it could also shed light on the cause of the EEG readings taken during lucid dreams [25]. Electrically stimulating the fastest electrical waves produced inside the brain, or the lower gamma bandwidth, is thought to provoke a greater sense of self-awareness while dreaming. Electrical stimulation can even induce a sudden change in state of consciousness, indicating that a person becomes lucid as soon as the stimulation begins [25]. Increased activity in the lower gamma band has been linked to mindfulness and self-awareness, possibly explaining why suddenly stimulating this band causes around three out of four people to become lucid [26]. Being able to induce lucidity on-command is certainly appealing when using lucid dreaming for therapeutic or research purposes, making electrical stimulation of the lower gamma band a promising avenue for future lucid dreaming research.

Trans-cranial direct electrical stimulation (tDCS) is another method of electrically stimulating the brain, allowing researchers to target specific brain regions [27]. When used to stimulate frontal regions of the cortex, tDCS increases the chances that a lucid dream will occur in a given sleep session [28]. However, lucidity is not immediately induced, and the positive effect of tDCS only applied to already-experienced lucid dreamers, possibly because lucid dreamers already have a more active prefrontal cortex [28]. Uncovering an effective and consistent means of inducing lucid dreaming will provide invaluable benefits to lucid dreaming research, and can even benefit people who suffer from chronic nightmares.

Taking Control of Your Worst Nightmares: The Clinical Applications of Lucid Dreaming

Imagine that you are in the midst of an extremely vivid and terrifying nightmare. Perhaps you are being chased down a narrow hallway by a grotesque monster, or re-experiencing a traumatic event. Often during these petrifying dreams, we feel as though we have no choice but to sit through them until we wake up shaking and drenched in a cold sweat. However, in the last decade, a growing body of research has emerged to investigate lucid dreaming as a potential therapy for those with chronic, intense nightmares stemming from traumatic experiences [29, 30]. Chronic nightmares can significantly impact the quality of life of those who suffer from them; many patients experience these nightmares for decades and, in severe cases, existing therapy has failed to provide meaningful improvement [29]. 

Since lucid dreamers can often take control of the events and situations occurring in their dreams, lucid dreaming holds therapeutic potential in interrupting the nightmares of individuals with PTSD [30]. Lucid dreaming may work in tandem with Gestalt therapy and image reversal therapy (IRT), two traditional therapeutic approaches used to treat PTSD [30, 31]. During dream-specific Gestalt sessions, a therapist helps the participant safely re-experience the nightmare by discussing and interpreting it [30]. IRT works similarly to Gestalt therapy; however, IRT patients are often asked to rewrite or envision an alternate ending to their nightmares at the end of the session [31]. Individuals who participate in Gestalt and IRT exhibit a profound reduction in nightmare frequency [31, 30]. However, people who undergo these therapies in combination with lucid dreaming therapy experience only a slight reduction in nightmare frequency and intensity over those who completed IRT and therapy alone [32, 33, 30]. Furthermore, no studies investigate LDT in isolation, but rather explore it as a supplement to either Gestalt or IRT therapy. The existing body of clinical studies on lucid dreaming is small and methodologically flawed, and more research is needed to determine whether lucid dreaming has therapeutic potential. 

Dreaming Big: Current Shortcomings and Future Directions for Lucid Dreaming Research 

Thanks to recent popular media such as Inception and internet message boards, interest in lucid dreaming has increased rapidly in the last thirty years. While the body of research investigating the neuroscience and psychology behind lucid dreaming has been expanding, delving into these studies’ findings can sometimes present an unclear picture. A common limitation of the research discussed so far is that many findings are strictly correlational [16, 17]. Correlational research can be helpful in studying certain aspects of lucid dreaming; but, it fails to tell us about the mechanisms that underlie lucid dreaming. Therefore, additional research should incorporate EEG and fMRI technology, both of which allow for more direct research into the neural components of lucid dreaming. Current research also lacks widespread replication, or the recreation of existing research to ensure that findings were not made in error or due to a statistical anomaly [1]. 

Replicating studies can become difficult, however, when existing research contains vague and inconsistently defined terms. In lucid dreaming research, there is little consistency in defining what constitutes a “frequent lucid dreamer.” This is because different studies use inconsistent operational definitions to quantify lucid dreaming. Operational definitions are simply what researchers use to quantify nebulous concepts. The use of operational definitions is helpful in making a study easy to read and in letting researchers measure things that do not have a strict definition. That said, operational definitions can be problematic when comparing results across studies in which the same term is operationally defined in a different way. For example, some researchers dub individuals who experience lucid dreams naturally as  “frequent lucid dreamers,” while other researchers use the phrase to refer to people who have trained themselves to regularly lucid dream [19]. The existence of different operational definitions means that two studies can draw conclusions about “frequent lucid dreamers,” while actually referring to two completely different groups. 

Lastly, one of the largest obstacles in lucid dreaming research is consistently inducing and reporting lucid dreams. Even with the most tried-and-true induction methods, like MILD, some participants may have never actually learned how to lucid dream, or may infrequently induce them [30]. Studies that rely on self-reporting measures are not reliable because participants can falsely report that they experienced a lucid dream [34]. Since we know that lucid dreamers can “scan” the scene of their dream by moving their eyes back and forth, pre-agreed eye movements (PAEM) could be used to determine when someone is entering a lucid dream. [35]. While the use of PAEM in tracking lucid dreams is still largely hypothetical, scanning is one way to ensure that problems with self-reporting do not interfere with the conclusions of lucid dreaming research.

Sweet Dreams

Lucid dreaming research has undoubtedly come a long way in the last three decades; but, there is still a lot of ground to cover in understanding this exciting phenomenon. Fortunately, lucid dreaming is both safe and accessible for most people to try with just a little practice. While we still don’t know everything about lucid dreams, there is one thing we do know: they’re really fun! Continuing research ensures that this once unknown aspect of dreaming is becoming more popular and better understood with time. Not to mention, work on clinical applications means that lucid dreaming may one day be used to relieve nightmares. Now that you understand how lucid dreaming works, consider trying it out yourself — after all, there are no downsides! Lucid dreaming for the first time can feel immensely liberating, beautiful, and stimulating. See for yourself what it feels like to live in a world of pure imagination.

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