REM Sleep Deprivation: Don’t stay up, get some rest.
Sleep is something that is very important to our bodies, but unfortunately many people tend to neglect. Nowadays, adolescents not only have homework, extracurricular activities, jobs, and sports, but they also consume many types of media like tv shows, movies, as well as social media like Instagram late into the night. According to the Youth Risk Behavior Surveys administered by the CDC in 2015, 72.7% of high schoolers weren’t getting an adequate amount of sleep. We have also recently seen that during the pandemic, there has been an increase in social media consumption. There are many adolescents who aren’t getting enough sleep, and their bodies can feel the effects.
A recent study was done to test how REM sleep deprivation affects the learning and memory of adolescent mice. This study was conducted by researchers at Shaanxi Normal University in China and Huazhong University of Science and Technology and was published in 2020 (Chang et al). These findings could help us better understand how REM sleep affects our cognitive functions and show us the importance of getting enough sleep each night.
During sleep there are four distinct sleep stages that make up one sleep cycle, and throughout an entire night of sleep people will complete a few sleep cycles. Out of the four sleep stages, there is one stage known as REM (Rapid-Eye-Movement) sleep, while the rest are known as NREM (non-REM) sleep. During REM sleep, our brain activity almost mimics the brain activity of a person who is awake.
REM sleep is theorized to be important to cognitive functions such as memory and learning. Therefore, a lack of REM sleep could adversely affect and hinder these same cognitive functions. (Rasch and Born 2012) Synaptic plasticity is how effectively neurons send signals to each other, or the change in how strong the signals are between neurons (What is synaptic plasticity 2018). The synaptic plasticity is regulated by the ECB (endocannabinoid) system. REM sleep deprivation decreases synaptic plasticity, leading to weaker connections between neurons. This weaker connection is what leads to hindered cognitive functions.
The endocannabinoid system regulates bodily functions through chemical signals sent by neurotransmitters. The chemical signals sent by these neurotransmitters are received by receptors. (Aremu and Pietro 2021). The signaling of these receptors regulate the synaptic plasticity in the hippocampus, the part of the brain that is involved in memory and learning. (Carey et al. 2011). When these receptors are blocked by antagonist, it stops the receptors from receiving the chemical signals. This results in changes to the regulation of synaptic plasticity.
The main study is a response to earlier theories and prior research about REM sleep deprivation and its effects on cognitive abilities. One prior study revealed that sleep deprivation impairs the synaptic plasticity in the hippocampus. (Abel et al. 2018).
Another study explored the important role the ECB system plays in overseeing the balance of excitatory and inhibitory synapses within the hippocampus (Hilard et al. 2015). The main study was conducted because of these respective studies, and tested whether REM sleep deprivation influences the ECB system to investigate effects of sleep deprivation among adolescents.
In this test there were four distinct groups of mice, a control group, a REM sleep deprived group, a non-REM sleep deprived group that took an inhibitor, and a REM sleep deprived group that took the inhibitor. The method for REM sleep deprivation used was the multiple platform method, during which the mice were placed in an enclosure with multiple small platforms that were barely above a pool of water for twenty-four hours. This was done to increase stress to help keep the mice from falling asleep. The mice then underwent different behavioral tests to assess different effects of REM sleep. The groups of mice tested with the inhibitor were injected fifteen to thirty minutes after being trained and were allowed to rest for fifteen to thirty minutes before their behavioral tests.
For the behavioral tests, there was an open field test where mice roamed around an arena for six minutes while their distance and the time spent in the central area was recorded. There was an elevated plus maze, which consisted of arm-like areas that could be opened or closed. The distance traveled as well as time spent in the open arms versus the closed arms was recorded. Finally, there was an object place recognition test where for the first run mice got accustomed to the arena and the location of three objects for ten minutes. After twenty-four hours one object was moved, and the mice were given three attempts each six minutes to explore the new positions. How much time they spent exploring the newly placed object compared to the others was recorded. After the behavioral tests the researchers removed and then examined the mice’s brains through brain slice preparations, whole cell recording, and western blots.
The study concluded that REM sleep deprivation did hinder the mice during the spatial memory behavioral test. It was also found that the inhibitor successfully blocked the cannabinoid receptor and was able to reverse the effect of REM sleep deprivation. The mice with the receptor injection scored similarly to the control group mice in the memory behavioral test. However, scientists admit that within this topic similar experiments have yielded different results. There are different parameters that can change the results of the behavioral tests such as different types of behavioral tests, methods for sleep deprivation, environmental stress levels during behavioral tests, and duration of sleep deprivation.
This research study was conducted on mice, but mice and human ECB systems behave differently. Therefore, the next step might either be an animal that has an ECB system that more closely resembles a human’s ECB system, or maybe a human trial. We can study the brain through in vivo neuroimaging techniques such as MRIs, PETs, or SPECTs, to allow us to inspect the ECB system. This research would allow us to see if there is any possible correlation to how the human ECB system is impacted by REM sleep. The research on the antagonist could lead to exploring the possibility of a drug that might be able lessen the negative effects of REM sleep deprivation.
Once we fully understand the science of sleep and its importance there might be changes in society surrounding our concepts about sleep. We might have later start times for students going to school, later work starting hours for certain jobs, and more forgiving late-night hours. We also might treat those who suffer sleep deprivation better, as well as move toward a more balanced work/life approach to allow for healthier amounts of sleep. This would lead higher quality and quantity of sleep in the general public, leading to improved efficiency in work, school, and an overall boost in health conditions. Overall society would be more productive and function better due to better cognitive function.
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