Why Your Brain Needs to Dream

Research shows that dreaming is not just a byproduct of sleep, but serves its own important functions in our well-being.

BY MATTHEW WALKER, The Greater Good Science Center

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We often hear stories of people who’ve learned from their dreams or been inspired by them. Think of Paul McCartney’s story of how his hit song “Yesterday” came to him in a dream or of Mendeleev’s dream-inspired construction of the periodic table of elements.

But, while many of us may feel that our dreams have special meaning or a useful purpose, science has been more skeptical of that claim. Instead of being harbingers of creativity or some kind of message from our unconscious, some scientists have considered dreaming to be an unintended consequence of sleep—a byproduct of evolution without benefit.

Sleep itself is a different story. Scientists have known for a while now that shorter sleep is tied to dangerous diseases, like heart disease and stroke. There is mounting evidence that sleep deprivation leads to a higher risk of obesity andAlzheimer’s disease. Large population studies reflect a saddening truth—the shorter your sleep, the shorter your life. Not only that, sleep helps us to hold onto our memories and to learn facts and skills faster, making it important for everyone including infants, students, athletes, pilots, and doctors.

Much of this I outline in my new book, Why We Sleep: Unlocking the Power of Sleep and Dreams, which summarizes the many findings we have about sleep and its function in our lives.

But what about dreaming? Does it also have a purpose?

Recent work in my neuroscience lab and the work of other scientists has shown that dreams may have a very particular function important to our well-being. Here are the two main ways dreams help us.

Dreaming is like overnight therapy

It’s said that time heals all wounds, but my research suggests that time spent in dream sleep is what heals. REM-sleep dreaming appears to take the painful sting out of difficult, even traumatic, emotional episodes experienced during the day, offering emotional resolution when you awake the next morning.

REM sleep is the only time when our brain is completely devoid of the anxiety-triggering molecule noradrenaline. At the same time, key emotional and memory-related structures of the brain are reactivated during REM sleep as we dream. This means that emotional memory reactivation is occurring in a brain free of a key stress chemical, which allows us to re-process upsetting memories in a safer, calmer environment.

How do we know this is so? In one study in my sleep center, healthy young adult participants were divided into two groups to watch a set of emotion-inducing images while inside an MRI scanner. Twelve hours later, they were shown the same emotional images—but for half the participants, the twelve hours were in the same day, while for the other half the twelve hours were separated by an evening of sleep.

Those who slept in between the two sessions reported a significant decrease in how emotional they felt in response to seeing those images again, and their MRI scans showed a significant reduction in reactivity in the amygdala, the emotional center of the brain that creates painful feelings. Moreover, there was a reengagement of the rational prefrontal cortex of the brain after sleep that helped maintain a dampening influence on emotional reactivity. In contrast, those who remained awake across the day showed no such dissolving of emotional reactivity over time.

That in itself doesn’t say anything about the role of dreaming. But we had recorded each participant’s sleep during the intervening night between the two test sessions, and we found that specific brain activity that reflected a drop in stress-related brain chemistry during the dream state determined the success of overnight therapy from one individual to the next.

Dreaming has the potential to help people de-escalate emotional reactivity, probably because the emotional content of dreams is paired with a decrease in brain noradrenaline. Support for this idea came from a study done by Murray Raskind on vets with PTSD, who often suffer debilitating nightmares. When given the drug Prazosin—a medication that lowers blood pressure and also acts as a blocker of the brain stress chemical noradrenaline—the vets in his study had fewer nightmares and fewer PTSD symptoms than those given a placebo. Newer studies suggest this effect can be shown in children and adolescents with nightmares, as well, though the research on this is still in its infancy.

The evidence points toward an important function of dreams: to help us take the sting out of our painful emotional experiences during the hours we are asleep, so that we can learn from them and carry on with our lives.

Dreaming enhances creativity and problem-solving

It’s been shown that deep non-REM sleep strengthens individual memories. But REM sleep is when those memories can be fused and blended together in abstract and highly novel ways. During the dreaming state, your brain will cogitate vast swaths of acquired knowledge and then extract overarching rules and commonalties, creating a mindset that can help us divine solutions to previously impenetrable problems.

How do we know dreaming and not just sleep is important to this process?

To continue reading, visit Why Your Brain Needs to Dream

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