Dreaming Beyond Rem Sleep: Is It Possible?

Dreaming is defined as a series of thoughts, images, or emotions occurring during sleep. While it was initially believed that dreaming only occurs during REM sleep, it is now understood that dreams can occur during non-REM sleep as well. This was discovered in the 1960s, but the misconception that dreaming only occurs during REM sleep persists.

REM sleep is characterised by rapid eye movement, and the body essentially becomes paralysed. Dreaming during REM sleep is often associated with more complex, vivid, and emotional dreams. However, it is important to note that dreams during non-REM sleep are still possible and can be recalled.

Research has shown that dreaming is more likely to occur when slow waves in central and posterior brain regions are sparse, small, and shallow. Dreaming is also associated with the activation of arousal systems during non-REM sleep.

The types of dreams you have may differ depending on the sleep stage you are in. Dreams during REM sleep are often easier to remember and are longer with more unique words. On the other hand, dreams during non-REM sleep tend to be shorter and less intense.

Dreaming in non-REM sleep: a high-density EEG study of slow waves and spindles

Dreaming in NREM Sleep: A High-Density EEG Study of Slow Waves and Spindles

Francesca Siclari, Giulio Bernardi, Jacinthe Cataldi, and Giulio Tononi

Dreaming can occur in both rapid eye movement (REM) and non-REM (NREM) sleep. We recently showed that in both REM and NREM sleep, dreaming is associated with local decreases in slow wave activity (SWA) in posterior brain regions. To expand these findings, here we asked how specific features of slow waves and spindles, the hallmarks of NREM sleep, relate to dream experiences. Fourteen healthy human subjects (10 females) underwent nocturnal high-density EEG recordings combined with a serial awakening paradigm. Reports of dreaming, compared with reports of no experience, were preceded by fewer, smaller, and shallower slow waves, and faster spindles, especially in central and posterior cortical areas. We also identified a minority of very steep and large slow waves in frontal regions, which occurred on a background of reduced SWA and were associated with high-frequency power increases (local "microarousals") heralding the successful recall of dream content. These results suggest that the capacity of the brain to generate experiences during sleep is reduced in the presence of neuronal off-states in posterior and central brain regions, and that dream recall may be facilitated by the intermittent activation of arousal systems during NREM sleep.

Dreaming outside of REM sleep

Sleep can be divided into four stages, the first of which is the lightest, where your heart rate and breathing slow down and your muscles relax. The second stage is when your heart rate and breathing slow down even more, and your body temperature drops. The third stage is when your body falls into a deep, restorative sleep, which is important for healing muscles and promoting growth and development. The fourth stage is REM sleep, where your brain becomes active, your eyes move quickly, and your heart rate and blood pressure rise.

It was previously thought that dreaming only occurred during REM sleep, but this has since been disproven. Dreaming can occur during the early, non-REM stages of sleep as well. However, the types of dreams you have may differ based on the stage of sleep you are in. Dreams that occur during REM sleep are often easier to remember, are longer, and are rated as more vivid, emotional, and physically engaging.

Research has shown that dreaming during non-REM sleep is associated with fewer, smaller, and shallower slow waves, particularly in central and posterior brain regions. Dreaming is more likely to occur when slow waves are sparse, small, and shallow, especially in posterior and central brain regions.

One study found that lucid dreams, where the dreamer is aware that they are dreaming, can occur during both REM and non-REM sleep. This suggests that while lucid dreaming mostly occurs during REM sleep, it is possible for it to happen during the first and second stages of the sleep cycle.

Overall, it is clear that dreaming can occur during both REM and non-REM sleep, and that the characteristics of dreams can differ depending on the stage of sleep.

REM sleep vs non-REM sleep: what's the difference?

Sleep is a normal body process that allows your body and brain to rest. While it might seem as simple as closing your eyes and nodding off, sleep is anything but simple. In fact, modern medicine's understanding of sleep, what it does and how it works is just getting off the ground.

There are two types of sleep: REM (rapid eye movement) sleep and non-REM sleep. A sleep episode begins with a short period of non-REM sleep, before progressing through three non-REM stages, and finally to REM sleep. After the first REM cycle, you start a new sleep cycle and go back into non-REM sleep, and the cycle starts over.

The first distinction to be noted between REM and non-REM sleep relates to recall rates, which led to the original controversy about 'REM = dreaming'. An extensive review demonstrated that recall rates are considerably higher in REM sleep (81.9%) compared to non-REM sleep (43%). However, recall rates for non-REM may vary depending on the sleep stage—dream recall is at its highest during the first non-REM stage and lowest during the third.

The second key difference between REM and non-REM sleep relates to report length. Studies have consistently found that REM sleep reports are longer than non-REM sleep reports.

Thirdly, REM and non-REM sleep reports tend to differ in their qualitative character. REM sleep reports are typically rated as more intense, bizarre, perceptually vivid, emotional and physically engaging than non-REM sleep reports, which are more thought-like and conceptual.

During REM sleep, your eyes move rapidly behind your closed eyes, your heart rate speeds up, and your breathing becomes irregular. In contrast to other stages of sleep, in which your brain waves slow down, your brain is highly active during REM sleep, and your brain waves become more variable.

During REM sleep, much of your body operates similarly to how it does when you're awake, except your eyes are closed and you experience a temporary loss of muscle tone. Researchers have hypothesised that this is a protective measure, meant to stop you from acting out your dreams and injuring yourself.

You experience your first cycle of REM sleep about 60 to 90 minutes after falling asleep. As part of a full night's sleep, you cycle through four stages of sleep multiple times: three stages of non-REM sleep, followed by one stage of REM sleep. Each cycle through all the sleep stages takes 90 to 120 minutes to complete. With each new cycle, you spend increasing amounts of time in REM sleep, with most of your REM sleep taking place in the second half of the night.

All sleep is important, but REM sleep in particular plays an important role in dreaming, memory, emotional processing, and healthy brain development.

Dreaming

A majority of your dreams take place during REM sleep. However, REM is not the only stage in which dreams occur—that's actually a common myth about sleep. That said, the dreams you experience in REM sleep are usually more vivid than non-REM sleep dreams.

Emotional Processing

Your brain processes emotions during REM sleep. Dreams, which are more vivid in REM sleep, may be involved in emotional processing. Also, your amygdala, the part of your brain that processes emotions, activates during REM sleep.

Memory Consolidation

During REM sleep, your brain processes new learnings and motor skills from the day, committing some to memory, maintaining others, and deciding which ones to delete. Some memory consolidation also takes place during deep sleep, a non-REM stage.

Brain Development

Researchers hypothesise REM sleep promotes brain development, since newborns spend most of their sleep time in REM. Adding to the evidence is that animals born with less developed brains, such as humans and puppies, spend even more time in REM sleep during infancy than those that are born with more developed brains, like horses and birds.

We need the most REM sleep as infants and children, when our brains are still developing. Newborn babies spend eight hours in REM sleep each day. By adulthood, we only need an average of two hours of REM sleep each night.

Multiple studies of both humans and animals suggest that being deprived of REM sleep interferes with memory formation. However, memory problems associated with a loss of REM sleep could be due to overall sleep disruption, since those often occur together. Also, studies of the few rare individuals who do not experience REM sleep show that they do not experience problems with memory or learning. That said, REM sleep deprivation disrupts the brain's ability to generate new cells. More research is needed to better understand the effects of REM sleep deprivation.

Do people dream during non-REM sleep?

It was long believed that dreaming only occurred during REM sleep, but this has since been disproven. Dreaming can occur during the early, non-REM stages of sleep, too.

The stages of sleep

After you fall asleep, your body goes through four stages of sleep. The first three are non-rapid eye movement (NREM) sleep, and the fourth is rapid eye movement (REM) sleep.

The discovery of REM sleep

The claim that dreaming only happens during REM sleep spread in the early 1950s when Eugene Aserinsky, then a physiology student, ran an experiment on his 8-year-old son. Aserinsky hooked up his son to a machine that measured brain activity and recorded his "rapid eye movement" — the first scientific report of REM. Aserinsky's discovery took off in the news and elevated the study of sleep.

The myth debunked

However, further sleep studies on adults showed that dreaming can occur during non-REM sleep, too. In one study, researchers awakened sleep subjects during the first few minutes of their sleep cycle. Over half of them were able to describe their dreams. Another study found that lucid dreams can occur in both REM and non-REM sleep.

Differences between REM and non-REM dreams

While you can dream during any sleep stage, the types of dreams you have may differ based on the stage you're in. REM sleep dreams are often longer and easier to remember. They also tend to be more vivid, emotional, and physically engaging. Some researchers describe them as more complex in their story-like structure.

Do you only dream in REM sleep?

Dreaming is defined as "a series of thoughts, images, or emotions occurring during sleep." While it was initially believed that dreaming only occurs during REM sleep, it is now known that dreams can occur during non-REM sleep as well.

REM sleep is characterised by rapid eye movement and is the fourth stage of sleep. The first three stages are non-REM sleep, which is further divided into N1, N2, and N3. During REM sleep, the eyes move quickly behind the eyelids, the heart rate and blood pressure rise, and breathing becomes faster and irregular. Dreaming during this stage is associated with arms and legs that cannot move, which prevents people from acting out their dreams.

Non-REM sleep, on the other hand, occurs during the first three stages of sleep. During N1, the body is still relatively alert and can be easily awakened. In N2, the heart rate and breathing slow down even more, and the body temperature drops. N3 is a deep, restorative sleep that is important for healing muscles, promoting growth and development, and boosting immunity.

While it is true that dreaming is more common and more vivid during REM sleep, it is not limited to this stage of sleep. Dreams can also occur during non-REM sleep, particularly in the early stages of sleep (N1 and N2). However, these dreams tend to be shorter and less intense, with a lower recall rate compared to dreams during REM sleep.

The types of dreams experienced may also differ between REM and non-REM sleep. Dreams during REM sleep are often longer and include more unique words, making them easier to remember. They are also rated as more vivid, emotional, and physically engaging, with a more complex story-like structure. In contrast, dreams during non-REM sleep may be more thought-like and conceptual.

In conclusion, while dreaming is more commonly associated with REM sleep, it is not limited to this stage of sleep. Dreams can occur during non-REM sleep as well, but they tend to have different characteristics and are less likely to be recalled.

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