13 Brain Activation in Normal versus Lucid Dreaming

Superstitions surrounding the origins of dreams were quite common in ancient cultures. Some believed dreams were messages sent by gods or spirits. When dreams were brought to religious leaders such as priests or shamans, they would decipher a “divine message” within the dream. The message usually contained helpful insights or predictions. One example is in ancient Greece, citizens suffering from physical ailments would sleep in the temples of the god Asclepius where they would receive “divine dreams” that when brought to a priest for interpretation would prescribe treatment for their ailments (Wamsley, E.J., 2013). Although this was a popular belief among many cultures, there was no scientific evidence. One of the first people to attempt a scientific approach to dream theory was Sigmund Freud. He developed analytic dream theory in the early 20th century which stated that dreams were the key to accessing the unconscious mind. Even though his theory may have followed scientific procedures, it did not have empirical evidence to support it.   Furthermore, a common misconception up until the 1950’s was the predominant belief that the brain was “turned off” during sleep with little to no brain activity processing occurring (Wamsley, E.J., 2013). However, current research has demonstrated that many brain regions are active during sleep (Wamsley, E.J., 2013). There is still debate concerning the origins of dreams, but they are often explained as thoughts and images we experience during sleep consisting of information received during wakefulness  (Wamsley, E.J., 2013). Everyone experiences multiple dreams every night, but most dreams are forgotten upon awaking. A common misconception is that dreams only occur during REM (rapid eye movement) sleep, a sleeping state where the eyes move rapidly behind closed eyes and brain activity increases. However, dreaming also occurs during NREM (non-rapid eye movement) sleep which is characterized by slower brain waves and less brain activity compared to REM. Although dreaming is experienced during all sleep stages, we experience the most vivid and intense sleep mentation in REM sleep (Dresler et al., 2012). The development of EEG, fMRI, and PET technology (see Cognitive Neuroscience Methods chapter) has been essential for the progression of research in brain activity during sleep and dreaming.

Lucid versus non-lucid dreaming

Non-lucid dreams (AKA normal dreams) are experienced by everyone. During non-lucid dreaming, the dreamer is not aware that they are sleeping and may not be able to tell if their experience is real. In contrast to lucid dreaming, which occurs more often during REM sleep,  normal dreaming occurs regularly in all sleep stages. There are three stages of NMREM sleep. although each stage consists of unique mental processes, these stages are all characterized by slowing down of breathing, muscle activity, heartbeat, and brain waves (Sleep Foundation, 2023). Stage one and two of NREM sleep are considered light sleep, and stage three is considered deep sleep (Sleep Foundation, 2023). As mentioned above, the origins and purpose of dreaming are still unknown although there are many theories.

As mentioned in the introduction, lucid dreaming consists of cognitive features of waking and dreaming (Dresler et al., 2012). As a result, the dreamer can often control the dream, passively observe the course of the dream and on occasion, even wake themselves up from the dream (Schredl et al, 2022), but these features can vary depending on the dreamer and the dream. Any aspect of a lucid dream can be altered, from the environment to the storyline and even the people. The content of lucid dreams is on average more pleasant than that of non-lucid dreams due to the dreamer’s ability to control their actions and the activities in the dream (Schredl et al., 2022). Lucid dreaming often occurs during REM sleep but there are rare cases of lucid dreaming occurring in NREM sleep (Stumbrys & Erlacher, 2012).  As stated by Dresler et al. (2012), in comparison to non-lucid REM sleep, lucid dreams are associated with increased 40-Hz activity and increased coherence in frontal regions shown by quantitative EEG data. Not everyone experiences lucid dreaming. Schredl & Erlacher (2011) estimated only about half of the population has at least one lucid dream in their lifetime. Although research on lucid dreaming has progressed significantly, it is not known why only some people experience lucid dreaming. Age may be a factor, as it is more common in children and young adults.

Brain activation during lucid versus non-lucid dreaming in fMRI and EEG data

FMRI and EEG technology are commonly used to study brain activity during sleep. A case study conducted by Dresler et al. (2012), combined EEG and fMRI with the aim of “revealing the neural correlates of lucidity per se by contrasting lucid vs. non-lucid REM sleep.” Four experienced lucid dreamers were recruited for the study (however, only one became lucid twice while under EEG/fMRI conditions – making it a case study). During the study, participants slept in an fMRI scanner under concurrent polysomnographic (EEG/EOG/EMG) monitoring for two to six successive nights (fifteen nights in total). The participants were to perform a simple task immediately after becoming lucid. In the lucid dream, they were instructed to move their eyes from left-right-left-right (LRLR), then clench their left hand for ten seconds, repeat the LRLR sign, then clench their right hand for ten seconds. Participants would repeat these signals for as long as possible.

The results of this study showed many cortical areas significantly activated during lucid REM sleep that are deactivated during non-lucid REM sleep. An increase in activity was found in the right dorsolateral prefrontal cortex, the parietal lobules, the bilateral frontopolar areas, the bilateral cuneus, the occipitotemporal cortices, and the strongest increase in activation observed occurring in the precuneus during lucid REM sleep shown in Figure 1.  Functions of these brain regions vary vastly; the dorsolateral prefrontal cortex is associated with self-focused metacognitive evaluation. Activation in the parietal lobules and simultaneous activation in the dorsolateral prefrontal cortex may suggest working memory demands relating to the task performed in the study. The bilateral frontopolar areas are related to the processing of internal states for example, evaluation of thoughts and feelings. The bilateral cuneus and occipitotemporal cortices are a part of the ventral stream of visual processing, involved in several aspects of conscious awareness in visual perception. Finally, the precuneus is a brain region implicated in self-referential processing, such as a first-person perspective and experience of agency.  Dresler et al. (2012), discussed the support of these findings in recent quantitative EEG data that show the wake-like state is paralleled by neural activations in the frontal and frontolateral regions (Voss et al., 2008). Furthermore, PET data has also shown cognitive control in dreams is associated with activation of the frontal cortex components  (Shapiro et al., 1995). The data obtained from the study by Dresler et al. (2012) suggests lucid REM dreaming is characterized by the regaining of these higher cognitive abilities that are deactivated during non-lucid dreaming. These higher cognitive abilities may be what enable the dreamer to be aware of the dreaming state.