The Future of the Neuroscience of Dreaming

Posted by Susan Lubejko on March 11, 2021 in Dreams, Neuroscience, Sleep | Leave a comment

What is the purpose of dreaming? What do the contents of your dreams mean? What is your brain doing during dreams to produce the sometimes surreal experiences that leave you confused upon waking? Why do we remember some parts of our dreams, but struggle to recall the events in others?

The unsatisfying answer to these questions is that neuroscientists, psychologists, and sleep experts don’t really know. Dreams are, of course, the predominantly visual (and other sensory) experiences we have mainly during the rapid eye movement (REM) phases of sleep. It is generally hypothesized that dreaming occurs to help us sort through memories of the day to solidify the memories we need, discard the ones we don’t, process our feelings of the events, and perhaps prepare us for a future dangerous situation [1]. Other researchers have recently posited that dreaming keeps our visual cortex, the part of the brain that processes complicated visual information, in tip top shape in the absence of actual input from the eyes so that those neural pathways are ready to process vision again the next day [2]. 

Sleep neuroscientists have recorded brain waves during dreams to understand what kind of activity is necessary to produce these complicated sensory scenes during sleep. A 2017 study by researchers in Wisconsin and Switzerland found changes in the frequency of brain activity in the parieto-occipital cortex, an area of the brain devoted to processing sensory information, that could predict whether, upon waking, patients would report that they were dreaming [3]. Another study shows in a small group of participants that the motor cortex, which controls bodily movement, becomes active during dreams in which a motor movement is being performed [4], although REM sleep is usually accompanied by paralysis of muscles that prevents acting out the movement during sleep.

While research is being done on dreams in sleeping animals and humans, the findings often barely scratch the surface of the questions posed above. So, why is it so hard to ascertain these details? As you might expect, studying dreams is really hard. This is primarily because dream studies often rely on subjective reports from participants that have just woken up to report the specifics of what they experienced in their dreams. If you are the kind of person that doesn’t remember any of their dreams, you can imagine how difficult this type of reporting is. Even if you are the type that remembers details of extremely vivid dreams, you probably experience the details slipping away as soon as you wake up.

What if there were a way for dreamers and researchers to communicate with each other during the dream itself?

A brand new study from scientists in four research groups across the globe endeavored to do just this [5]. The researchers took advantage of the concept of lucid dreaming to establish two-way communication with sleeping participants. Typical dreamers tend to not be aware that they are in a dream until after waking, accepting all of the crazy events of their dreams as reality in the moment. Lucid dreamers, however, are conscious of the fact that they are dreaming during the dream, which allows for a measure of control over the dream’s events (For more information on lucid dreaming and tips on how to try lucid dreaming yourself, check out this NeuWrite article!)

During the study, a total of 36 lucid dreamers were instructed to move their eyes, one of the only body parts whose muscles aren’t paralyzed during REM sleep, from left to right 3 times once they achieved lucid dreaming. After recognizing this signal, the researchers asked most of the participants simple math questions (i.e. 4 plus 1) either through spoken language or flashing light stimuli (see this NeuWrite article for more information on how the brain processes external sensory information while we sleep). Before the study, the dreamers were instructed to use the same eye movements to answer these math questions (for example, 4 plus 1 would elicit a response of 5 left to right eye movements). In 40% of trials, the participants indeed responded to the math questions. Of those responses, almost half of them were correct, while the other half was composed of ambiguous and a few incorrect responses. One participant in France was even able to answer yes/no questions by contracting specific muscle groups in their face during a lucid dream.

The study reveals some pretty amazing results about two-way communication with sleeping individuals. First, it was clear to the researchers that this communication was not simply a fluke produced by random eye darting that occurs during REM sleep. Since the participants were instructed to move their eyes in large movements from the extreme left to the extreme right of their eye sockets, the possibility of mixing up normal eye movements with these intentional ones was relatively low. Also, the task required participants to perceive, understand, calculate, and respond to a question. While these simple math expressions seem easy to us conscious individuals, this amount of processing to produce a response has not been previously seen in those that are asleep.

Finally, the techniques used in this study shed light on the popular method of using dream reports from recently awake individuals to understand dreaming. In this study, participants were quizzed when they woke up about their experience during the lucid dream. Interesting differences were noted in how the math problems entered their consciousness during the dream, with some participants perceiving the spoken instructions as a recording over the events of the dream and others finding them incorporated into the dream itself (i.e. perhaps a radio in the dream began playing the mathematical expression). Most strikingly, when the newly awake dreamers were asked to repeat the math problem they solved, many of them got it wrong, demonstrating that verbal reports of dreams can be full of inaccuracies.

While the brain activity and associated perceptions during dreaming are still shrouded in mystery, neuroscientists are hard at work studying the many questions we have about the purpose and meaning of dreams. The new research presented above may just help in the crusade to study dreaming in real time. There is potential for two-way communication between dreamers and scientists to evolve into ways to probe the contents of dreams as they are experienced, without having to rely on dream reports after the fact. Asking dreamers to reveal their dreams as they have them without relying on faulty memories may open a whole new realm of research to provide insight into some of our most difficult-to-answer questions about this common yet mysterious part of our lives.

References

1. Healy, B (2019) Bad dreams are good. The Atlantic.
2. Eagleman D, Vaughn D (2020) Why do we dream? A new theory on how it protects our brains. Time Magazine.
3. Siclari F, et al. (2017) The neural correlates of dreaming. Nature Neuroscience, 20(6):872-878
4. Dresler M, et al. (2011) Dreamed movement elicits activation in the sensorimotor cortex. Current Biology, 21:1833-1837
5. Konkoly KR, et al. (2021) Real-time dialogue between experimenters and dreamers during REM sleep. Current Biology, 31:1-11

Cover Image Source: Country Living Magazine, countryliving.com