Crash Course Psychology #9 is where I learn about sleeping and theories as to why we dream.
For context, Crash Course inspired me to learn the basics of psychology, so I’ve made it my mission to watch the entire Crash Course Psychology playlist and paraphrase each episode in my own words. This journey wouldn’t have been possible without the Crash Course team, so many thanks to them! To showcase what I learnt, here is my personal paraphrase of episode 9:
What and Why we Sleep
Sleep is just another state of consciousness. It is not the brain or body shutting down. Technically speaking, sleep is a periodic, natural, reversible and near total loss of consciousness. This makes it different from hibernating, being in a coma, or being under anaesthesia.
We spend around 1/3 of our lives asleep and we know it’s vital for health and survival, but Science still haven’t concretely concluded why we sleep. Here are what Science thinks so far;
- Recuperation
- Allows our neurons and other cells to rest and repair themselves
- Growth
- It is during sleep that our pituitary glands release growth hormones, which is why babies sleep all the time
- Mental Function
- Sleep improves memory, giving brains time to process what we experience in day time and boosts creativity
How we Sleep
While we don’t know the exact reasons why we sleep, we know a lot of how we sleep. We use the Electroencephalograph, or (EEG) machine that measures the brain’s electrical activity. It was in the early 1950’s that grad student Eugene Aserinsky used this machine on his son. There he discovered that the brain doesn’t just “power down” during sleep, as many scientists thought. Instead, he discovered the sleep stage that we now call REM.
Rapid Eye Movement (REM) is a recurring sleep stage during which vivid dreams commonly occur. It’s an interesting, not yet fully understood, period of sleep where the brain is full of activity despite it and the body being asleep.
Sleep specialists use technology similar to the EEG and have shown that we experience 4 distinct stages of sleep, each defined by unique brainwave patterns. The 4 stages are; Rapid Eye Movement (REM), NREM-1, NREM-2, NREM-3. The cycle goes like this;
The Sleep Cycle
0) During the day, your endocrine system keeps you awake by releasing “awake” hormones like cortisol by the Adrenal Glands.
0.5) Arrival of the night, your endocrine system releases “sleepy” hormones like melatonin by the Pineal gland. Your brain gets relaxed but still awake, a level of activity measured by EEGs as Alpha Waves. This is that feeling of sleepiness and slowed breath just before falling asleep.
1) The moment you fall asleep is clearly evident on an EEG reading because those Alpha Waves immediately transition in to waves that look obviously different. This is the irregular non-Rapid Eye Movement stage one (NREM-1) waves. It’s in this first stage that we may experience Hypnagogic Sensations, which are those weird moments of falling in your bed.
2) As you further relax, you move to NREM-2 stage sleep. This is where your brain shows bursts of rapid brain wave activity, called Sleep Spindles. Here, you’re definitely asleep.
3) Then comes NREM-3 stage sleep, indicated by the slow rolling Delta Waves. It is up to this point, in these first three stages, that you can have brief and fragmentary dreams.
4) The most important stage of sleep, full REM sleep. Most known for when your eyes move like crazy while you are asleep and this is where your vivid dreams happen. During this time, the motor cortex sends signals, but the brainstem blocks them, leaving your body essentially paralyzed except for the eyes.
Finally, this whole sleep cycle repeats itself every 90 minutes or so.
Sleep Deprivation
Lack of sleep causes a myriad of problems, making it a killer blow to your health, mental ability, and mood.
It’s a predictor for depression. It can cause weight gain because it disrupts hunger arousing and suppressing hormones. It causes immune system suppression and slows reaction time.
Sleep Disorders
- Insomnia
- recurring problems in falling or staying asleep.
- Narcolepsy
- a sleep disorder characterised (sometimes) by uncontrollable sleep attacks (brief overwhelming sleepiness). Not the hallmark symptom of Narcolepsy, but worth noting. Narcolepsy may have several different causes, including a deficiency of the neurotransmitter Hypocretin which keeps you awake.
- Sleep Apnea
- a sleep disorder that causes the sleeper to temporarily stop breathing (until the lack of oxygen wakes them).
- REM Sleep Behaviour Disorder
- We don’t fully understand this yet
- Night Terrors
- Characteristics include increased heart and breathing rates, screaming, and thrashing. May have several causes which include stress, fatigue, sleep deprivation and sleeping in unfamiliar surroundings. Occurs during NREM-3 stage of sleep, just like sleepwalking and sleeptalking. This is not the same as Nightmares, which occur during REM sleep.
Dreams
Not known for certain, but we have some ideas:
- Even though we get crazy dreams sometimes, it’s mostly our brains unpacking and reshuffling what we did the day before. So whatever you did during the day, you may dream about it.
- Our 2 track minds allows us to register more stimuli than we outwardly acknowledge. Dreams can therefore incorporate stimuli you might not have even noticed.
Why do we dream?
Also not known for certain, but we have some ideas:
- Wish-fulfilment Theory: Sigmund Freud with his 1900 book “The interpretation of Dreams”, proposed that dreams offer us wish-fulfilment. However, this theory lacked scientific evidence and mostly has fallen.
- Information processing Theory: Proposes that our dreams help us sort out and process the day’s events and fix them into our memories.
- Physiological Function Theory: Suggests that dreaming may promote neural development and preserve neural pathways by providing the brain with stimulation. Brains expand their connections more upon stimulation.
The are other theories. One argues that dreams are part of our cognitive development, suggesting that dreams draw from our knowledge and understanding of the world, mimicking reality. Another theory, the neural activity model, focuses on the way REM sleep triggers neural activity, positing that dreams are merely accidental side-effects.
Oneirology: The study of dreams. It’s a mix of neuroscience and psychology.
Conclusion of Crash Course Psychology #9
For now, scientists continue to debate the function of dreams. However, one thing we know for certain is that REM sleep is vital for us, both biologically and psychologically. Imperative to our health!
Questions after Crash Course Psychology #9
- The theory that argues that dreams are part of our cognitive development, what is that theory called?
Enjoyed this learning of Psychology? Test your knowledge against these quick custom Kahoot! quizzes I’ve made based on the episode above: This is the easy mode and this is the hard mode for Crash Course Psychology #9.
Also, do check out what else Psychology related I’ve learnt from my Psychology blog!
Credits for Crash Course Psychology #9
Original Content & Media by Crash Course
Content Consumed and Paraphrased by Danniel Iskandar
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