Research-related theories on sleep and dreaming.

I journal about my dreams. I like to document the workings of my unconscious mind and evaluate what I may be processing during sleep. But how much should we really pay attention to our dreams and nightmares? How much of it is meaningful, and how much of it is just random noise?

Researchers have been fascinated with these questions for over a hundred years and are still grappling with some of the same questions today. A review article on sleep and dreams was published in 2020. In the following sections, we’ll briefly summarize and discuss that review.

Neural Mechanisms That Underlie Our Dreams

When we dream, we’re in a distinct physiological state. Several neural mechanisms keep us safe when we dream. For example, our peripheral motor output is blocked when we dream, so that we don’t act out our dreams. Similarly, sensory input is dampened, which may intensify the visual inputs from our dreams.

One of the earliest hypotheses to explain dreaming is from 1977. Researchers developed the Activation-synthesis model that involves internally generated brain activation in lower-level brain regions (e.g., brain stem). Then, this information is processed by other brain regions, such as the visual cortex, and with this processing, we experience visually-rich dreams.

These processes, however, can go awry. People with restless leg syndrome or REM (rapid eye movement) behavioral disorder experience movement while asleep and may even act out their dreams.

Why We Dream

People have proposed several theories to explain why we dream. Some believe that dreams are nothing but random noise from brain activity during the rapid eye movement sleep stage.

Most others believe that dreaming has a purpose. Nightmares could potentially prepare us for threats and challenging situations. Others propose dreaming improves creativity, and rapid eye movement sleep, in particular, helps us integrate and connect initially unrelated ideas. Relatedly, dreaming helps us solve problems, possibly through the imagery within our dreams .

Some sleep researchers believe that dreaming helps strengthen and consolidate memories, such that neural replay of memories stabilizes them into long-term memories. Interestingly, some have theorized that sleep disruptions may lead to psychiatric disorders. We’ll go over these theories below.

How Nightmares Could Help Us

Nightmares could help us prepare for challenging events. If we have experienced a stressful situation, even if only in our dreams, we may be better able to handle it when it comes up again. Perhaps visualization (during wake) is a highly recommended preparation strategy because it familiarizes us with and primes us for upcoming challenges.

However, there is some criticism of this idea. Because dreams are often unrealistic representations of threats, they may not adequately prepare people for them.

When Sleeping Goes Awry: Psychopathology

One of the most interesting theories of sleep and dreams is that our sleeping brains prune or “unlearn” events of the waking day that are unimportant. We intake massive amounts of information everyday. We see people, pets, and vehicles. We read articles. We skip through advertisements. We work on several tasks. Even if we are at home all day, we encode the sensory properties of our environments, and because we live in a highly connected world, we are just a finger press away from endless streams of content. Not all of this information is necessary to store in our long term memories. Some researchers believe that sleep helps us get rid of the insignificant episodes of our lives — the monotony, the randomness that does not matter.

But, this unlearning process can go awry when we don’t get the sleep we need. Researchers have proposed that poor sleep may explain some aspects of psychopathology, particularly obsessive and intrusive thoughts that are similar to schizophrenia symptoms. It may become more difficult to let go of some ideas when we don’t sleep well.

This unlearning hypothesis is similar to the synaptic downscaling hypothesis of memory. Some memories may become more salient when we are able to let go of others. Perhaps we forget what’s unimportant to make mental space for what truly matters.

Dreams have fascinated people for many years. Some believe dreams are meaningless. Others believe our dreams have important functions, such as threat preparation, creativity and problem solving, and memory consolidation. Importantly, our dreams may also protect us against developing obsessive, repetitive, and unwanted thoughts.

Taken together, the sleeping brain is an active one. When we sleep, our dreams may help us prepare for the day ahead, allowing us to be creative, remember important details, and stay mentally well. What do you dream about?

Notes

• For an excellent academic review of sleep and dreaming, see “What are the neural mechanisms and physiological functions of dreams?” by Tomomi Tsunematsu.
• To see an overview of how I’ve documented my dreams using digital and analog methods, see this tiny blog. 

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