Struggling to prioritize sleep? Here’s some motivation.
Imagine your head hitting the pillow. Darkness encompasses the room, your eyes are closed, your breathing is melodically slow. Before you know it, you’re asleep. We all know the amazing relief that comes from resting after a long day. The time is almost sacred. In a world full of distractions, sleep is foreignly quiet.
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Yet, sleep is often cast to the side. When finals week arrives, college students boast of pulling ‘all nighters’ to get through studying. With a big deadline on the horizon, professionals grab a cup of coffee and work at all hours.
Sleep becomes negotiable in the checklist of daily tasks. In 2016, the CDC found that one in three adults don’t get enough sleep¹.
The benefits of sleep are ingrained in each and every one of us: performance, mood, energy. But, the impact of sleep is far greater. New research has shown that sleep affects brain health and function.
Sleep promotes memory formation, emotional processing, and synaptic plasticity.
If you need motivation to prioritize sleep, look no further. Here’s everything you need to know about sleep, it’s different cycles, and how this benefits the brain.
Your Sleep Cycles: REM vs N-REM
There are two types of sleep that occur each night: REM and Non-REM (N-REM). REM stands for rapid eye movement. It was first discovered in 1953 by Aserinsky and Kleitman².
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When you are first falling asleep, you experience a change from consciousness to unconsciousness. This first stage is non-REM sleep. As you enter a light sleep, basic, or homeostatic functions, of your body slow. Examples include lower temperature, brain activity, and heart rate³.
About 90 minutes after you fall asleep, you fall into the first cycle of REM sleep. REM sleep is characterized by eyes darting side to side. During this stage, your vitals are much closer to wakefulness. Your neural activity heightens, your breathing becomes fast, and your blood pressure elevates⁴.
Throughout the night, your body cycles between N-REM and REM sleep. But, the cycles are disproportionate. Your body experiences N-REM sleep for the majority of the night.
The difference between N-REM and REM sleep, you could say, is night and day. They use different neurotransmitters, or chemical messengers in your brain, and brain regions.
Neurons in the brain send signals to other neurons as a form of communication. These signals are electrochemical. Imagine such activity as a song. A fast rhythm indicates high activity, and a slow rhythm indicates greater rest.
N-REM sleep has a slow rhythm. During N-REM sleep, cortisol and acetylcholine levels decrease⁵. These are neurotransmitters associated with stress, heart rate, and muscle activation. They are often released by the brainstem and forebrain.
[Left] Photo by Luca Ambrosi on Unsplash [Right] Photo by Yegor Denisov on Unsplash
REM sleep has a fast rhythm. REM sleep activates the limbic system of our brain. This includes areas associated with memory, emotional processing, and learning⁶. The limbic system activates the cingulate gyrus, hypothalamus, lower brainstem (i.e. pons and medulla) and amygdala. REM sleep also activates the occipito-temporal visual cortex. This area of the brain controls visual perception⁷.
Acetylcholine is a neurotransmitter released by the limbic system. Recent studies found that acetylcholine levels are four times higher in REM sleep than N-REM sleep⁸.
The difference of these cycles matters. While you’re sleeping, your brain is strengthening its health because of their variance.
Neurologic Benefits of Sleep
Sleep alters the environment of your brain. As a result, it uniquely boosts your brain health. This article focuses on three:
Memory encoding
Synaptic plasticity
Emotional processing
Memory Encoding
Memory formation happens in three phases: encoding, consolidation, and retrieval. The perfect example of this process is test taking. You receive a study guide, study it, and then use the information at a later date.
N-REM sleep is essential for the second stage of memory making. This consolidation phase processes information from your environment. The thalamus transfers this information to the hippocampus for long term storage⁹.
The slow rhythm of N-REM sleep facilitates this. N-REM sleep suppresses the release of cortisol and acetylcholine¹⁰. This suppression promotes communication between the hippocampus and thalamus.
Synaptic Plasticity
Synaptic plasticity measures the strength of brain cell communication. The end of neurons are synapses. They release the signals needed for communication.
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Recalling memory is like a sport. The more your practice, the better you perform.
The networks of specific memories decay over time if they aren’t used. Think of N-REM sleep as our brain’s practice time. By promoting hippocampal activity, it strengthens the networks of our memories¹¹.
Sleep strengthens your brain function beyond memory.
Researchers are working to understand the relationship between synaptic plasticity and sleep. The synaptic homeostasis hypothesis (SHH) is one theory gaining credit.
The entire SHH hypothesis is based on long term potentiation (LTP). This describes the strength between neuronal communication. Sleep optimizes brain function by promoting rest and work¹².
SHH states that during sleep, neurons ‘downscale’ synaptic activity. This helps makeup for the fast-paced rhythm of wakefulness¹³. Continuing the analogy of sports, sleep is like targeted exercise. The brain downshifts areas that are most active during the day. This rest promotes optimal performance while awake. Work is also promoted. Neurons that are less used, such as hippocampal ones, are activated so that they don’t decay.
It’s important to note that this theory needs greater research and evaluation.
Emotional Regulation
REM sleep regulates our emotional attachment to memories.
The limbic system regulates how our emotions connect to experiences. During REM sleep, this area is activated. This promotes emotional processing of whatever stimuli the day brings. REM sleep also has higher activity in subcortical and cortical nodes. This suggests that newly formulated memories may be sent to areas of the brain for regulation and understanding¹⁴.
REM sleep also suppresses adrenaline and histamine hormones. This low-stress environment is ideal for emotional processing. It allows for processing with minimal stress. Studies have found that 75-90% of REM dreams have emotional context¹⁵.
One study measured the emotional processing of depression in newly divorced women. Researchers compared the dreams of women with depression compared to those who had been in recovery for one year. Recovered women had significantly more dreams of their exes. This suggests that sleep may process traumatic experiences as part of optimal functioning.
“Sleep to forget.”
This notion has become popular in the last few years due to new research. In 2019, a study used rats to measure brain activity during sleep. The study found that the slow oscillations of N-REM sleep promote learning and memory. But, they also found that faster, ‘delta waves’ occurring REM sleep promote forgetting¹⁶.
The difference between REM and N-REM sleep, again, plays a role in forgetting. REM sleep activates the amygdala, or emotion processing area, but not the hippocampus, used for memory.
It’s important to note that nightmares also occur during REM sleep.
1/20 people suffer from weekly nightmares¹⁷.
There are many factors that play a role in this. Mental illness, PTSD, stress, and anxiety all increase an individual’s chance of having nightmares. These psychological conditions have a physiological impact on the brain. For example, PTSD patients may detach from their emotions as a coping strategy. But, in the long run, this creates irregularities in limbic activity¹⁸. While REM sleep can play a role in positive emotional processing, it can also perpetuate a night-day cycle of anxiety.
Studies have shown that sleep deprivation causes the following emotional disturbances¹⁹:
Increased emotional reactivity
Decreased ability to distinguish social cues
Increased associations between fear and long term memories
You are more likely to perceive someone’s mannerisms as negative when sleep deprived
Sleep is a beautifully complicated process. One the one hand, the slow pace of N-REM sleep promotes memories and connectivity. But, REM sleep disconnects areas to prompt emotional healing and forgetting. Like a scale, your brain works during sleep to balance the two.
Much research still needs to be known about neurologic benefits of sleep. But, it’s clear that the complicated patterns of sleep are purposeful.
While you’re sleeping, your brain is working.
Endnotes:
1 in 3 adults don't get enough sleep. (2016, February 16). Retrieved July 28, 2020, from https://www.cdc.gov/media/releases/2016/p0215-enough-sleep.html
Mancia M. (2004). The dream between neuroscience and psychoanalysis. Archives italiennes de biologie, 142(4), 525–531.
Murillo-Rodriguez, E., Arias-Carrion, O., Zavala-Garcia, A., Sarro-Ramirez, A., Huitron-Resendiz, S., & Arankowsky-Sandoval, G. (2012). Basic sleep mechanisms: an integrative review. Central nervous system agents in medicinal chemistry, 12(1), 38–54. https://doi.org/10.2174/187152412800229107
Ibid
Feld, G. B., & Born, J. (2017). Sculpting memory during sleep: concurrent consolidation and forgetting. Current opinion in neurobiology, 44, 20–27. https://doi.org/10.1016/j.conb.2017.02.012
Peterson, N. D., Henke, P. G., & Hayes, Z. (2002). Limbic system function and dream content in university students. The Journal of neuropsychiatry and clinical neurosciences, 14(3), 283–288. https://doi.org/10.1176/jnp.14.3.283
Paulson, S., Barrett, D., Bulkeley, K., & Naiman, R. (2017). Dreaming: a gateway to the unconscious?. Annals of the New York Academy of Sciences, 1406(1), 28–45. https://doi.org/10.1111/nyas.13389
Walker, M. P., & van der Helm, E. (2009). Overnight therapy? The role of sleep in emotional brain processing. Psychological bulletin, 135(5), 731–748. https://doi.org/10.1037/a0016570
Ibid
Ibid
Ibid
Wang, G., Grone, B., Colas, D., Appelbaum, L., & Mourrain, P. (2011). Synaptic plasticity in sleep: learning, homeostasis and disease. Trends in neurosciences, 34(9), 452–463. https://doi.org/10.1016/j.tins.2011.07.005
Ibid
Ibid
Ibid
Key to Learning and Forgetting Identified in Sleeping Brain. (2020, July 27). Retrieved July 28, 2020, from https://www.ucsf.edu/news/2019/09/415501/key-learning-and-forgetting-identified-sleeping-brain
Rek, S., Sheaves, B., & Freeman, D. (2017). Nightmares in the general population: identifying potential causal factors. Social psychiatry and psychiatric epidemiology, 52(9), 1123–1133. https://doi.org/10.1007/s00127-017-1408-7
Ibid
Ibid
Siclari, F., Baird, B., Perogamvros, L., Bernardi, G., LaRocque, J. J., Riedner, B., Boly, M., Postle, B. R., & Tononi, G. (2017). The neural correlates of dreaming. Nature neuroscience, 20(6), 872–878. https://doi.org/10.1038/nn.4545