Sleep is a biological need for humans to survive. There are several theories that give reason to what happens when we sleep that range from evolutionary perspectives to the why we dream. Sleep is regulated by the circadian rhythm which is a biological clock that tells the body when to sleep based on environmental factors like daylight. Several environmental factors have affected the average times people go to bed like screens and artificial light. Overall, sleeping is a physiological need and it keeps people alive and well.
The first stage of sleeping begins with NREM 1 which stands for non-rapid eye movement. This stage includes feeling sensations of falling when you are not and the term for this is hypnagogic sensations. NREM 1 also makes people hallucinate. This is the beginning of the process of sleep; brain waves begin to slow, heartbeat slows, and breathing rates begin to slow. This stage only takes up five percent of how much you sleep throughout the night.
The second stage of sleeping is called NREM 2. Similar to NREM 1, this stage is still setting up your body for deep sleep. What disassociates this stage from NREM 1 is the brain activity. During NREM 2, brain waves are slow, but every now and then there are random spikes in energy. These spikes are called sleep spindles and K-complexes and they are associated with the brain organizing memories and learning. This stage is significantly longer than NREM 1 as it takes forty-five percent of sleeping each night.
The last stage before REM sleep is NREM 3. This is where dreams begin to occur because of the deep state of sleep you are in. Brain activity is very slow but exhibits great amplitudes on EEG scans (electroencephalogram - a way to record brain activity). The length of this stage changes throughout a persons lifetime to where an infant needs a significantly longer time in NREM 3 than their grandparents, but on average it takes up around twenty-five percent of sleep. This is because this stage is associated with developing the immune system and repairing injuries, which is something you would think older people would need. If you do not get enough sleep during NREM 3, it can lead to sleep deprivation.
After all the stages of non-rapid eye movement stages occur, the brain enters REM sleep (rapid eye movement). This is where most dreams occur and the body is paralyzed. This stage is critical to your well being as a person. During this stage your brain is processing everything from new information to past events in your memory, and without this people would be where they are today.
The importance of sleep has been debated by several theorists which has led to discussions on why we dream. There are five different theories to why we dream: Wish Fulfillment Theory, Information Processing Theory, Physiological Function Theory, Activation Synthesis Theory, and Cognitive Theory. Wish Fulfillment Theory was developed by Sigmund Freud which says that dreams allow us to fulfill unconscious desires. Information Processing Theory is a theory that says we dream to organize information from earlier that day. Physiological Function Theory says we dream to repair and grow our bodies. Activation Synthesis Theory explains that during dreams our brain processes our neural impulses from the body to the brain stem. Lastly, Cognitive Theory explains that dreams help the brain consolidate memories and thoughts.
Why do you think we sleep and dream?
Sources:
Myer's Psychology Textbook 3rd Edition
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