Lucid dreaming; conscious while asleep?

Last update: February 20, 2024
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Reading time: 4 minutes
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By Brain Matters

Last year, I listened to one of my fellow Master students explaining that some people can control their dreams by realizing that they were dreaming. I got intrigued about this type of dreaming better known as lucid dreaming. It struck me that while you dream you have literally endless possibilities to give structure to these and do whatever you want! For this reason even if you have already read the previous article about lucid dreaming, I would like to elaborate a bit more on this intriguing idea of being ‘conscious’ while asleep.  

Besides me, many researchers became interested in studying the brain basis of conscious states and demonstrating how voluntarily training lucid dreaming can change these states. However, how to actually measure this dreaming condition remained rather difficult, since no tools to objectively measure this were available until the 1970s. The electrooculogram (EOG) which is a measure to pick up electrical signals caused by voluntary eye movements made it for the first time possible to do so. Based on prior research showing that participants can voluntarily move their eyes in a distinct sequence to show that they are lucid-dreaming at that time point, sparked the idea to measure these voluntary eye movements by making use of EOG. The most common eye signaling technique currently used in research is asking participants to signal when they realize that they are dreaming to  rapidly look left and right two times consecutively and then back to the center (left-right-left-right eye signals). In combination with subjective reports of the participant mentioning the lucid dreaming episode, measuring their electroencephalogram (EEG) while they are sleeping forms the golden standard to objectively indicate if a person is lucid dreaming.

The eye signaling technique as measured by EOG in combination with EEG opened the gateway towards studying brain activity in lucid dreamers. At first, researchers thought that lucid dreaming was a rapid eye movement (REM) sleep (dream sleep) phenomenon, since it usually emerged during this type of sleep. However, research is slowly moving toward the hypothesis that lucid dreaming is a hybrid state between being awake and in REM sleep. Researchers have started exploring this hypothesis by comparing the brain’s electrical activity when a person is awake, in non-lucid REM sleep, and in lucid REM sleep. 

An example of such a study is a study by Voss and colleagues. They measured the EEG and EOG activity of 6 undergraduate students at Bonn University, who were able to lucid dream after following four months of weekly lucidity training sessions. Interestingly, the electrical activity measured in these 6 students during lucid REM sleep was not comparable to the electrical activity measured during either their waking state or while they were in non-lucid REM sleep. Normally when you are awake your electrical activity in the brain is characterized by high alpha power (one of the electrical brain waves or oscillations named after their frequency, other examples are beta, gamma, etc.). In this study, the researchers showed that when students were awake, they had significantly higher alpha electrical activity in their brains compared to when they were in lucid REM sleep or non-lucid REM sleep. Moreover, in the case of gamma power, this was significantly elevated when the students were in lucid REM sleep compared to when they were awake or in non-lucid REM sleep.

What does this mean you might wonder?  Normally, alpha power is often associated with a state of wakeful resting. However, when we are lucid dreaming our brain is quite active, since we have to control our own dream. This could explain why gamma power is increased during lucid REM sleep and not during eyes open resting or non-lucid REM sleep. This increase in gamma power was especially seen in the frontal parts of the brain. This is in accordance with the fact that lucid dreaming is a dreaming state characterized by regaining higher cognitive capabilities such as the awareness that you are dreaming. This is in contrast to non-lucid REM sleep, where neural activity in these areas is decreased, leading to visual hallucinations, emotional experiences or you seeing yourself randomly fighting a dragon for no reason. 

According to the research described above, it seems quite likely that lucid dreaming is a hybrid state of consciousness, since it shows measurable differences in electrical activity compared to awakeness and non-lucid REM sleep. However, a review by Dresler and colleagues points out that most studies investigating lucid dreaming,  like the study described earlier, have very few participants and therefore replication of findings remains difficult. Specifically, the increase in gamma power in frontal parts of the brain can be influenced by eye movements itself. This makes it difficult for researchers to interpret this increase in electrical activity, since fully filtering out the influence of these eye movements is not possible (yet). Therefore, we cannot be certain that lucid dreaming indeed is a hybrid state of consciousness. Maybe after a couple of years and more large-scale EEG studies including more participants, we can unravel this mysterious phenomenon of  lucid dreaming.. 

Author: Joyce Burger

Illustration: Joyce Burger

References:

  • Baird, B., Mota-Rolim, S. A., & Dresler, M. (2019). The cognitive neuroscience of lucid dreaming. Neuroscience & biobehavioral reviews, 100, 305-323. 
  • Dresler, M., Wehrle, R., Spoormaker, V. I., Koch, S. P., Holsboer, F., Steiger, A., Obrig, H., Sämann, P. G., & Czisch, M. (2012). Neural correlates of dream lucidity obtained from contrasting lucid versus non-lucid REM sleep: a combined EEG/fMRI case study. Sleep, 35(7), 1017-1020. 
  • Hobson, A. (2009). The neurobiology of consciousness: Lucid dreaming wakes up. International Journal of Dream Research, 2(2), 41-44. 
  • Voss, U., Holzmann, R., Tuin, I., & Hobson, A. J. (2009). Lucid dreaming: a state of consciousness with features of both waking and non-lucid dreaming. Sleep, 32(9), 1191-1200. 
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