How Dreams Help Us Think

By Julia Zeng (Director of Journal)

“Sleep on it” is a common saying in response to problems that have no solution in sight. The importance of getting 8 or 9 hours of sleep each night has become widespread knowledge. As humans sleep, their brains cycle between periods of non-rapid eye movement (NREM) sleep, also called “deep sleep,” and rapid eye movement (REM) sleep. Advocates of long restful nights of sleep often cite the mental and physical benefits of NREM sleep, but less commonly discuss REM sleep and the impacts of what arguably is its most prominent feature: dreams.

Everyone dreams, even if we often don’t remember these dreams. Most dreaming takes place in REM sleep, which usually starts around 90 minutes after falling asleep. Humans in REM sleep have increased heart rates and decreased body temperature. Our muscles are also all paralyzed, except for those responsible for heartbeats, breathing, eye movements, and hearing. Although we typically don’t physically act out our dreams, our brains are still firing neurons in many of the same parts we use when awake. Connections between aspects of dreams and corresponding portions of the brain were also found for movement, thought, and spatial awareness. The study involved capturing brain activity while subjects slept, and waking them at various points in the night to ask questions about whether they were dreaming, and what they remembered about their dreams.

“Dreams are just thinking in a different biochemical state,” according to Harvard University psychologist Deirdre Barrett. One way that thinking in dreaming differs from conscious thinking is the lack of filtering by the prefrontal cortex. When we're awake, the prefrontal cortex helps us maintain focus on one task among the several that our brains usually run simultaneously. It also moderates our thoughts and behavior to make sure they are socially acceptable and logical. But when we're sleeping, this filter does not run. In addition, the brain removes smaller, weaker synapses (connections between neurons that form through learning) and reorganizes the memories that remain. This decluttering, combined with the lack of prefrontal cortex restraint, allow many thoughts that are repressed during the daytime to emerge into the foreground. In addition, levels of cortisol, a stress hormone, rises during REM sleep. Cortisol fractures memories, which are then recombined to form new associations. Our occipital lobe (visual centers at the back of the brain) displays increases in activity while we sleep. The occipital lobe shows an example of this rearranging as it pieces together aspects of different images to result in hallucinogenic visions during dreams. The cleaning and rearranging process provides an explanation for why our dreams often involve unrealistic experiences and thoughts that we typically bury.

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Evidence pointing to this recombination process occurring can be found in studies that show a link between dreaming and an enhanced ability to piece together seemingly unrelated concepts. In a 2009 study at the University of California in San Diego, subjects took a word analogy test that involved guessing the word that is related to three other given words. In the 90 minutes that followed, subjects either stayed awake, took a nap with REM sleep, or took an entirely non-REM nap. The subjects took a similar word analogy test after the resting period, where the correct answers to many questions were identical to answers from the previous test. While those who didn’t nap or napped without REM sleep between tests had lower scores when retaking the test, those who had REM sleep, where most dreaming takes place, scored 40% better after their nap.

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Perhaps this link between dreams and finding creative solutions can help lend merit to the age-old belief in sleeping on a problem. Since a good night’s sleep allows for enough time spent in the dream state, hopefully the link between dreams and creativity will give you another reason to sleep well tonight.

Vivian Lu