Most Common Dreams in the U.S.

How do different stages of sleep influence the content and nature of dreams?

Contrary to popular belief, dreams can occur during all the sleep stages instead of just REM sleep, with some differences. For example, dream reports from NREM sleep are often more thought-like and mundane, whereas dreams from REM sleep are more elaborate and vivid. Dreams are also more frequent during REM sleep than NREM.

Dreams are also more frequently reported during Stage 1 sleep (the transition between wake and sleep) compared to other NREM stages (Stage 2 and slow wave sleep), even though there’s debate on how we should categorize dreams from this stage, and they’re referred to as lucid dreaming, hypnagogic hallucinations, or micro dreaming.

How do external factors, like stress or sleep environment, impact the frequency and intensity of dreams?

External factors like stress can significantly affect the frequency and content of dreams. High stress can increase the frequency and intensity of emotions in dreams, potentially by activating a brain area named the amygdala that is important for emotion processing.

For example, during the COVID-19 pandemic, those who were more affected tended to report more dreams and heightened emotions during dreams.

What role does neurobiology play in the occurrence and recall of dreams?

Different models have used neurobiology to explain the mechanism of dreaming. Brain areas involved in emotional processing and memory, including the prefrontal cortex and limbic system, could be central to dream content.

However, as for now, there are no agreed-upon biomarkers of dreaming experience, which makes it difficult to drill down the specific neurobiological changes during dreaming.

Are there methods to enhance dream recall and clarity for research purposes?

There are studies showing that one can improve dream recall and clarity by simply practicing. Specifically, by keeping a dream journal every day and actively working on recalling dreams, one can remember more dreams with more details.

There are also devices that help us recall dreams, such as Dormio developed by a group at MIT, that is used to help people improve dream recall during stage 1 sleep, which might help with our creativity.

There are studies showing that dreaming about a memory task helps with its performance. Plus, the ability to recall a dream might have shared mechanisms with memory consolidation.

I have a paper that’s in the process of being published that shows that dreaming helps us forget irrelevant experiences (less emotionally salient information) while retaining more emotionally salient events. The exact mechanism linking memory consolidation and dreaming is still a subject of ongoing research, and I hope to see more research on this.

How do different stages of sleep influence the content and nature of dreams?

During sleep, the brain is more active in rapid eye movement (REM) sleep, showing activity similar to that seen during waking. This contrasts with the high amplitude slow waves seen during non-REM (NREM) sleep. The discovery of REM sleep, with its similar patterns of brain activity to waking, led to the suggestion that REM sleep was associated with dreaming – the vivid, conscious, internally-generated experiences we experience during sleep.

This view is supported by the fact that when subjects are woken from REM sleep, they are more likely to report dreaming than if woken during NREM sleep. However, later studies showed that up to 70% of NREM awakenings yield reports of dreaming. As such, dreams can occur during any sleep stage, though are more likely to be recalled after waking from REM sleep.

The study of dreams is challenging, as this depends upon test subjects reporting what the dream, rather than direct observation. Moreover, it is difficult to manipulate dream content experimentally (for example, by exposure to stimuli before or during sleep).

It is difficult to predict the content of dreams – so most research aims to relate neuronal activity to the general dreaming when the subject wakes up, rather than focusing on the specific content of dreams and trying to relate this to the activity observed.

Dreams often reflect a person’s interests and personality in the same way that mental activity during waking does. For example, personal anxieties – such as being late or inappropriately dressed.

However, a common feature is reduced voluntary control. Dreams are very visual, with color, shapes, and movement and they include features such as faces, places, objects, and animals. Sounds may also be experienced, and whilst rarer, touch, smell, taste, pleasure, and pain may also occur during dreams.

How do external factors, like stress or sleep environment, impact the frequency and intensity of dreams?

As we carry our daytime mental activity into our sleep, our prior experiences may affect dream content. Stresses during waking experience can therefore be incorporated into dreams. An example of this is when daytime activity involves ongoing repetitive tasks.

And some activities performed before sleep, such as playing video games, may influence the dreamlike experiences we have as we drift into sleep. The sleep environment may influence dream when this is sufficient to intrude upon consciousness, such as loud noises.

What role does neurobiology play in the occurrence and recall of dreams?

Some recent research on dreams has highlighted a ‘hot zone’ of posterior cortical regions (Siclari et al., 2017 Nature Neuroscience). Local decreases in low-frequency activity in this area is predictive of dreaming in both REM and NREM sleep.

High-frequency activity in this region was predictive of specific dream content. Monitoring this region may provide a way of telling whether subjects are experiencing dreams in real-time.

Are there methods to enhance dream recall and clarity for research purposes?

Studying dreams in the lab typically involves waking the test subjects every 15-30 minutes throughout the night to ask whether they were experiencing dreams. This is often combined with high density electroencephalography (EEG) and brain imaging.

Subjects can be trained in dream reporting too. And there is a lot of interest in ‘lucid dreaming’ – where the subject knows they are asleep but can influence dream content. This may relate to micro-arousals where subjects partially wake.

What are the potential links between dreams and cognitive processes like memory consolidation?

Whilst there is substantial research on the role of sleep in memory consolidation, the role of dreams in such processes are poorly understood. Some theories of sleep suggest that dreams may relate to creating simulations of the world or may occur due to replaying key circuits that were active during wake.

Alternatively, dreams may arise due to the brain attempting to interpret internally-generated stimuli, often from brain regions below the conscious cortex.