REM and Non-REM Sleep
In REM sleep, our bodies are temporarily paralyzed
REM (rapid eye movement) and Non-REM sleep are the two stages that occur during the night. Human slumber consists of 90 minute sleep cycles. There are 5 stages of light sleep, two of deep sleep, and a stage of REM. REM-sleep aides in problem solving and it is the stage when deep sleep occurs. Non-REM dreams are sparse and more thought like, often without complexity, and length. Non-REM dreaming is important for stabilizing and strengthening memories, and REM dreaming reorganizes the way a memory is stored in the brain.
How dreams are made
To have a dream, your brain first records an event in the hippocampus. Then it transfers the content to the cortex where it files the recollection for long-term storage. The memories themselves enter our dreams in 2 different stages: first floating into our consciousness on the night itself, then reappearing 5-7 days later. Additionally, there is a theory that memories surface into our dreams as different pieces of information are passed through the brain.
The hippocampus stores your memories
How dreams help us
The sleeping brain forges links, allowing you to see association between different events. There is also a theory that the "foundation of dreaming is weaving new material into the memory system in a way that both reduces emotional arousal and is adaptive in helping us cope with further trauma or stressful events." REM dreams strentgthen negative emotional memories, so we can learn from them. Day dreaming can improve our ability to take meaning from information and to have creative insights. Dream sleeps acts as a homeostasis.
Why people experience dreAms
Although the cause of why we experience dreams is still relatively unknown, scientists have been working on an answer. People experience dreams when when some specific situations trigger distinctive feelings. By thinking of a specific dilemma before bed, we can increase our chances that we will dream a solution. This event has happened to numerous people, including people like Dmitry Mendeleyev, who came up with his final form of the periodic table of the elements in his sleep. The event also happened to Mary Shelley, who dreamed the two main scenes that became "Frankenstein." Don Newman was also able to figure out the answer to a complicated math problem in his sleep, that had troubled him for days.
This picture shows what parts of the brain are active and inactive during sleep, and what the different parts do
Theorys about why we dream
Many scientists and researcher have studied dreams for decades. Theorys are constantly emerging, and scientists are working on proving them. One scientist believes that dreaming is simply a epiphenomenon (or by-product) of mental activity that occurs during REM sleep. The "Contemporary Theory of Dreaming" (CTD) states that dreaming is not random and is guided by the emotions of the dreamer. Scientists have learned that when the emotional state is less clear, or when there are several emotions or concerns at once, dreams become more complicated. CTD considers dreaming to be a broad making of connections guided by emotion. While most scientists are optimistic about the research they are finding about dreams, Jan Born and Susanne Diekelmann, who work at the University of Lübeck in Germany, argue that dreams have no meaning and are just a side effect of brain activity.
Next time you wake up, try to rember your dream. Was it about a past experience? Did you solve a problem? Did you strengthen your connection to a memory? Did you learn anything? These are all things scientists have to study to learn more about dreams, but most of the population can't recall any of the above. That's why the study of dreams will continue on for many decades until an answer is found.
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Young, E. (2011). The I in dreaming. New Scientist, 209(2803), 36