Dreaming is a universal human experience that is also very unique to every individual. It is a state of mind where individuals experience a reality like none other that exists when we are awake. In fact, dreaming is so different from the ordinary day to day that we live in, it is the place where many extraordinary and creative ideas are rumored to be thought of; everything from scientific breakthroughs such as Einstein's theory of relativity and Dmitri Mendeleev’s organization of the periodic table, to popular culture ideas such as the Beatles’ song Yesterday and Mary Shelley’s famous character, Frankenstein are rumored to be conceived in a dream.
Roland, E. (2018, April 27th.). 13 World-Changing Ideas that Came from Dreams (Literally). Retrieved June 2020, from https://www.rd.com/list/ideas-that-came-from-dreams/
To begin, let’s look at what your brain looks like in dreams. When people dream, they are typically in a part of the sleep cycle known as REM sleep or “rapid eye movement” sleep. During this sleep stage, research has shown that parts of the brain associated with memory (hippocampus), visual and spatial processing, motion, and places where emotional processing and generation increase in activity. This begs the question: if so many areas of the brain are activated while dreaming, why are dreams so easily forgotten?
Walker, M. (2017). Chapter 9: Routinely Psychotic, REM-Sleep Dreaming. Why we sleep: Unlocking the power of sleep and dreams.(pp. 193-205). Simon and Schuster.
A study from researchers Izawa et al. suggests that dreams are easily forgotten possibly because of sleep’s role in consolidating and forgetting memories. It is widely known that dreams mainly occur during a stage of sleep called rapid eye movement sleep (REM sleep). These researchers discovered that a group of hypothalamic MCH (melanin concentrating hormone) cells seemed to fire more frequently in a group of mice while they were in REM sleep. Thus, to test the possibility that MCH cells relate to forgetting in REM sleep, researchers genetically turned on and off MCH cells in mice to see how it affected their performance on memory tests. They found that mice sniffed familiar objects more (as if they had not previously encountered the object) when the MCH cells were turned on, showing that memory was worsened when MCH cells were more active. Thus, Dr. Thomas Kilduff, a researcher in the study, inferred from these results that part of why dreams are easily forgotten because MCH cells, which seem to play a role of letting go of certain information in the memory consolidation process, fire frequently during the REM stage of sleep which is where dreaming mostly occurs.
Summary by U.S. Department of Health and Human Services: https://www.nih.gov/news-events/news-releases/brain-may-actively-forget-during-dream-sleep
Original Article:
Izawa, S., Chowdhury, S., Miyazaki, T., Mukai, Y., Ono, D., Inoue, R., ... & Terao, A. (2019). REM sleep–active MCH neurons are involved in forgetting hippocampus-dependent memories. Science, 365(6459), 1308-1313.
So, why is it that some people tend to remember their dreams more than others? Is there anything we can do to remember more of our dreams? A preliminary study done at George Washington University attempted to answer these questions, considering the relationship between the level of interest in our dreams, and our recall. This study asked college students to record their dreams and examined how much students thought, believed, and discussed their dreams. This study concluded that there was a positive relationship between level of interest and recall. Although it is not a definite causal relationship, having a greater interest in your dreams may allow you to remember them better! Try paying attention to the content of your dreams and see if you can intentionally recall them upon waking. Keep a dream journal or talk to your roommate about your dreams.
Robbins, P., & Tanck, R. (1988). Interest in Dreams and Dream Recall. Perceptual and Motor Skills, 66(1), 291-294.
More research needs to be done about the categorization of our dreams, but it can be interesting to think about what our dreams tell us about our sleep. The next time you wake up, see if you can remember and categorize your dream!
Beyond remembering dreams, many people also question what their purpose is in the first place. Why is dreaming useful, if at all? Dr. Matthew Walker, a sleep specialist at UC Berkeley, has hypothesized that dreaming may help us process emotionally painful events, making them less painful with time. Dr. Walker came up with this theory by realizing that during REM sleep our brains completely stop the release of noradrenaline (a chemical related to stress) even while activating parts of the brain related to emotional processing and memory. Thus, he postulated that REM sleep allows us to relive painful experiences without the negative emotional baggage which ultimately helps us recover from them.
Dr. Walker tested the theory by putting participants in an MRI and having them look at emotional images. Half of the group slept (while being recorded by researchers) after seeing the images while the other group did not. After 12 hours, participants were shown the emotional images again. Dr. Walker found 3 key things. Those who slept had less amygdala activation (a portion of the brain associated with stressful feelings), reported feeling less emotional than the first time they saw the image, and had increased activation in the prefrontal cortex (an area responsible for controlling emotional reactions). Dr. Walker found that these elements were more closely related to the amount of time participants slept in REM sleep, not just sleep in general. The group that did not sleep had the same emotional reactivity as they did when they were initially exposed to the images. Therefore, sleep, but specifically dream sleep, can help us process the painful events that happen to us.
Walker, M. (2017). Chapter 10: Dreaming as Overnight Therapy. Why we sleep: Unlocking the power of sleep and dreams.(pp. 206-218). Simon and Schuster.
Just like sleep itself, dreaming has the potential to help us in ways we might not have expected.
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