You close your eyes — and your brain gets to work
Every night, something extraordinary happens while you sleep. Without realizing it, you embark on impossible narratives: you fly over unfamiliar cities, reunite with people who have passed away, run from threats that vanish when you wake up. Dreams are, perhaps, the most universal and mysterious experience of human existence. Almost every human being dreams — and almost every human being has woken up wondering: but why does this happen?
Science has been trying to answer this question for decades. Neuroscientists, psychologists, and sleep medicine specialists have accumulated fascinating discoveries about what happens in the brain during sleep, which regions activate, which hormones come into play, and what all this might mean for our mental and physical health. The result is a rich field of knowledge, full of solid consensus — and also of hypotheses still under debate.
If you’ve ever been curious about the origin of your strangest dreams, or if you’ve tried to understand why sometimes you wake with the feeling of having lived something real, this article is for you. We’ll explore what science actually knows about the act of dreaming.
What happens in the brain while we dream
To understand dreams, you must first understand sleep. It is not a uniform state: throughout the night, the brain goes through cycles that repeat on average four to six times. Each cycle has distinct phases, and the one most associated with vivid dreams is called REM — an acronym for Rapid Eye Movement.
During REM sleep, the brain displays electrical activity surprisingly similar to that of wakefulness. Regions linked to emotion, such as the amygdala and the anterior cingulate cortex, become very active. At the same time, the area responsible for logical thinking and critical judgment — the prefrontal cortex — has reduced activity. This helps explain why dreams seem so real while we’re in them, but so absurd when we try to describe them after waking up: the part of the brain that would detect inconsistencies is, literally, less “switched on”.
Furthermore, during REM there is a kind of temporary muscle paralysis — technically called muscle atonia — that prevents the body from executing the movements that happen in the dream. It’s a sophisticated protection mechanism that evolution developed so we don’t hurt ourselves while sleeping.
The main theories about the function of dreams
Why do we dream? Here’s the point where science still debates. There is no single universally accepted answer, but there are some well-founded hypotheses.
Memory consolidation
One of the most accepted theories is that dreams — especially those of REM sleep — play an important role in memory consolidation. During sleep, the brain seems to “replay” information from the day, transferring short-term memories to long-term storage. Research with groups of volunteers showed that people who sleep well after learning a new task perform better the next day than those who stayed awake. Sleep, and possibly dreaming, is part of this process.
Emotional regulation
Another much-studied hypothesis is that dreams help to process difficult emotions. American neuroscientist Matthew Walker, in his work on sleep, argues that the neurochemical environment of REM sleep — with reduced levels of noradrenaline, a substance linked to stress — creates a kind of “safe space” for the brain to revisit emotionally charged memories without the same traumatic impact. This would explain why we sleep and often feel calmer facing problems that seemed immense the night before.
Threat simulation
A theory of evolutionary origin, associated with Finnish researcher Antti Revonsuo, proposes that dreams function as a threat simulation. By “rehearsing” dangerous situations in a safe environment, the brain would be preparing us to respond better to them in real life. This would explain the frequency of nightmares and dreams of persecution — they would not be dysfunctions, but training sessions.
Creative thinking and problem-solving
There is also evidence that the dream state favors unusual connections between ideas — the type of thinking associated with creativity. Famous historical cases, such as that of German chemist August Kekulé, who is said to have arrived at the structure of benzene after a dream about a serpent biting its own tail, are frequently cited. Although anecdotes are not scientific proof, laboratory research shows that people in REM sleep tend to find more creative solutions to certain problems than those who are awake.
Why are dreams so strange?
If dreams have such serious functions, why are they so chaotic and illogical? The answer lies precisely in that reduction of prefrontal cortex activity. Without the rational “editor” working at full steam, the brain combines memories, emotions, and images in an associative and non-linear way. The result is narratives that mix people, places, and times in ways that would be impossible in reality.
Furthermore, the brain during dreaming seems to create a retroactive narrative: you don’t “watch” a finished script, but you build the story as it happens, trying to make sense of the images that emerge. That’s why dreams often have that sense of internal coherence that completely falls apart when we wake up and try to explain what happened.
Recurring dreams: what do they mean?
Recurring dreams are particularly intriguing. Research suggests they tend to be associated with unresolved stress, chronic anxiety, or emotional conflicts that the brain continues trying to process. Common themes — such as falling, arriving late to an exam, losing teeth, or not being able to run — appear in very different cultures around the world, which suggests that some emotional triggers are universal.
This does not mean that each dream has a fixed “hidden meaning” that can be deciphered like a code. The interpretation of dreams as revelation of deep truths — famous in Sigmund Freud’s psychoanalytic tradition, and later reread by Carl Jung — is a culturally powerful idea, but one that does not have solid empirical backing in contemporary neuroscience. What science says is that dreams reflect the emotional and cognitive state of the dreamer, not that they carry universal symbolic messages.
Who dreams more — and why we don’t always remember
All human beings dream, but not everyone remembers dreams with the same frequency. The ability to recall depends on several factors:
- How you wake up: waking up during or shortly after REM sleep greatly increases the chance of remembering the dream
- Sleep quality: sleep deprivation fragments cycles and makes it difficult to memorize dreams
- Stress and anxiety: can increase vivid dreams and nightmares, making them more memorable
- Alcohol use and certain medications: suppress REM sleep and reduce dreams
- Attention upon waking: people who stay quiet and try to remember right after waking are more successful
Children tend to dream more vividly than adults, and studies indicate that babies spend an enormous proportion of sleep time in REM phase — raising the hypothesis that this period is especially important for the development of the nervous system.
What dreams reveal about our health
In some cases, dreams function as a health indicator worthy of attention. Frequent nightmares may be associated with post-traumatic stress disorder (PTSD), depression, generalized anxiety, and other conditions. REM sleep behavior disorder — in which muscle atonia fails and the person physically acts out within the dream — is associated, in some studies, with increased risk of neurodegenerative diseases like Parkinson’s.
> Attention: the information in this article is educational and general in nature. If you suffer from recurring nightmares, sleep disturbances, or behaviors during sleep, seek evaluation from a doctor or sleep medicine specialist. Each case is unique and deserves individualized attention.
Lucid dreams — those in which the dreamer realizes they are dreaming and can, to varying degrees, influence what happens — are also the subject of serious scientific research. Techniques to induce them have been studied, and there is interest in their therapeutic application, especially in treating recurring nightmares.
Conclusion: the dream as a window into the brain
Dreaming is, at once, something absolutely everyday and profoundly enigmatic. Science has made great strides in understanding what happens in the brain during sleep, and the evidence points to real and important functions: consolidating memories, processing emotions, perhaps preparing us for future challenges. But many questions remain open, and that is part of the beauty of the topic.
What is already clear is that dreams are not random noise. They are, in some way, the brain working — reorganizing, feeling, connecting. And perhaps that is the most honest answer science can give for now: you dream because your brain never completely stops, even when you close your eyes.
If you’re interested in scientific and historical curiosities like this one, you’ll also enjoy checking out incredible historical facts that really happened — because reality, often, surpasses any dream.
