Sleep (Part 2) - Architecture and Stages
Don’t be fooled by the stillness of sleep. It is an illusion.
It is an active process of renewal, guided by the hidden choreography of sleep.
Each stage offers its own form of restoration, preparing you to awaken anew.
- Morpheus (probably)
With this in mind, let’s continue our journey through the world of sleep.
Section 2: Architecture of Sleep Stages
Think of sleep not as a straight road to restfulness, but a winding journey.
Your brain travels through different landscapes, each with its own rhythms and secrets.
There are quiet valleys where your body rests deeply (NREM sleep),
And mountain peaks of vivid dreams where your mind is extremely active (REM Sleep).
NREM sleep
NREM sleep encompasses 3 distinct stages (N1, N2, and N3/N4), progressively increasing in depth.
Stage 1 (N1): The Gateway to Sleep
The Transition Zone. This initial stage marks the shift from wakefulness to sleep.
It typically lasts only a few minutes and accounts for approximately 5% of your total sleep time.
Neurochemical symphony
This transitional stage is marked by a slowing of brain activity—
Melatonin levels remain high.
GABA begins to play a more calming role.
Physiological Changes
Heart rate, breathing, and muscle tension start to decrease.
Body temperature continues to drop slightly, promoting a state of relaxation.
You may experience occasional muscle twitches, known as “hypnic jerks”.
Vibrational Changes
Brainwave patterns shift from faster beta and alpha waves towards slower theta waves.
Signifies a shift towards deeper sleep stages
Stage 2 (N2): Deeper Relaxation
Occupies roughly half of our sleep
Neurochemical Symphony
Melatonin levels are sustained
GABA 's effect intensifies, further reducing neural activity
Physiological Changes
Further decrease in—
Muscle tension
Heart rate
Body temperature
We become less responsive to our external environment.
Vibrational Changes
Brainwaves are primarily dominated by theta (slow) waves.
Unique bursts of electrical activity (sleep spindles and K-complexes) occur in this stage.
Though not fully understood, these bursts likely help with memory and protect our sleep from disruptions.
Stages 3 & 4 (N3/N4): Deep Sleep (Slow-Wave Sleep)
“Minimal” brain activity
Neurochemical Symphony
Levels of acetylcholine and other excitatory neurotransmitters drop significantly.
These stages are crucial for physical and immune system restoration.
Physiological Changes
Heart rate, breathing, and blood pressure reach their lowest point during the night.
Muscles are deeply relaxed, and it becomes increasingly difficult to awaken from this stage.
Vibrational Changes
The hallmark of deep sleep is the presence of slow, rhythmic delta waves.
Associated with cellular repair, tissue growth, energy replenishment, and immune system enhancement.
Deprivation has significant consequences for both our physical and cognitive health.
REM Sleep: The Paradoxical Stage
Often referred to as the "dreaming stage"
(though vivid dreams can also occur in other stages of sleep)
Characteristics
Rapid, darting, horizontal eye movements,
Bursts of brain activity reminiscent of wakefulness,
And near-complete muscle paralysis.
Neurochemical Symphony
Dramatic shift in neurotransmitter activity,
Increased activity of acetylcholine, memory and alertness neurotransmitter
Heightened state of brain activity during REM sleep.
(Some parts even more active than when we’re awake)
Physiological Changes
Although the brain is highly active, the body becomes almost entirely paralyzed during REM sleep.
This mechanism ensures our safety during this vivid and sometimes intense stage of sleep.
Vibrational Changes
Brainwaves during REM sleep resemble wakefulness, with a mix of theta (slow) and beta (fast) waves.
Reflects a brain state conducive to creativity, emotional processing, and memory consolidation.
Section 3: The Importance of Sleep Architecture
Turns out, this intricate dance of sleep stages is vital for optimal well-being.
Each stage plays a unique role in restoring the body and mind.
NREM Sleep: Physical Restoration
Bodies focus on physical repair in deep sleep (N3/N4)—
Increased blood flow
Muscle regeneration
Tissue growth
Energy replenishment
Immune Function
Sleep provides a boost to our immune system (Besedovsky, Lange, & Born, 2012).
Sleep deprivation compromises the body's ability to fight off infections.
Clearing Cellular Waste
Deep sleep clears out metabolic waste products that accumulate during our waking hours (Xie et al., 2013).
This "brain cleanse" may protect cells from damage.
REM Sleep: Cognitive and Emotional Balance
Memory Consolidation
REM sleep is believed to play a significant role in consolidating certain types of memory—
Particularly those related to skills, facts, and emotional experiences.
Studies even suggest that the brain replays and strengthens memories during REM sleep (Walker et al., 2009).
Emotional Processing and Regulation
REM sleep may assist in processing emotions and regulating our mood.
Inadequate REM sleep is linked to increased irritability difficulty managing emotions (positive and negative).
Interestingly, changes in anxiety were linked to deep sleep, not REM, suggesting it might not be purely emotional (Walker & Ben Simon, 2018).
Creativity and Problem-solving
The heightened brain activity during REM sleep improve creative thinking and novel connections between ideas.
Getting sufficient REM sleep could enhance problem-solving skills and innovation.
What's Next?
Now you know why sometimes you feel like a zombie after a bad night's sleep.
But how do you actually fix it?
Next, we'll tackle sleep hygiene—and no, it doesn't mean showering before bed (though that wouldn't hurt).
Squeaks, Loss Prevention Officer
FAQ: Pharmacy School All-Nighters… Good or Bad?
My wife and I both preach the importance of sleep.
Ironically, we met my during a caffeine-fueled, sleep-deprived study marathon.
(… Let's just say sleep science wasn't on the syllabus that night)
Hindsight is 20/20 - Here's the sleep lesson we missed—
Study Reviews
Sleep Deprivation Impairs Memory Consolidation (Walker, 2017)
During sleep, particularly during NREM sleep stages, our brains consolidate and organize memories.
Skipping sleep in the nights leading up to an exam showed decreased in the ability to learn new facts by up to 40%.
Due to a drop in brain activity in the hippocampus, an area of the brain associated with memory.
This dramatic drop in recall ability is attributed to the diminished opportunity for the brain to process and store new knowledge during sleep.
Focus and Attention (Alhola and Polo-Kantola, 2007)
Lack of sleep negatively impacts your ability to focus and process complex information.
Lower cognitive performance and ability to make connections between new and existing knowledge
Crucial for deep learning and understanding
Practical Advice: What to Do Instead
Spaced Repetition is Your Friend
Instead of cramming all the material in one lengthy session, spread your study over multiple sessions with breaks in between.
This method, known as spaced repetition, helps to encode information more deeply into your memory.
Research shows that this technique substantially enhances long-term retention of knowledge (Kang, 2016).
Prioritize Sleep Hygiene
In the days leading up to an exam, ensure that you prioritize good sleep hygiene.
Regular sleep schedule, sleeping in a dark, quiet room, and avoiding caffeine close to bedtime
(As promised, more on this topic later…)
Students who sleep adequately perform better academically and retain information more effectively.
Strategic Napping (If You Must..)
If pulling an all-nighter seems unavoidable, opt for a short, strategic nap—about 20-30 minutes—to boost alertness and performance.
Avoid longer naps that could disrupt your normal sleep cycle
References:
Ben Simon, E., & Walker, M. P. (2018). Sleep loss causes social withdrawal and loneliness. Nature communications, 9(1), 3146. https://doi.org/10.1038/s41467-018-05377-0
De Andrés, I., Garzón, M., & Reinoso-Suárez, F. (2011). Functional Anatomy of Non-REM Sleep. Frontiers in neurology, 2, 70. https://doi.org/10.3389/fneur.2011.00070
Falup-Pecurariu, C., Diaconu, Ș., Țînț, D., & Falup-Pecurariu, O. (2021). Neurobiology of sleep (Review). Experimental and therapeutic medicine, 21(3), 272. https://doi.org/10.3892/etm.2021.9703
Fraigne, J. J., Torontali, Z. A., Snow, M. B., & Peever, J. H. (2015). REM Sleep at its Core - Circuits, Neurotransmitters, and Pathophysiology. Frontiers in neurology, 6, 123. https://doi.org/10.3389/fneur.2015.00123
Greater Good Science Center. (2018, November 6). Chronically anxious? Your brain may just be more “plastic”. Berkeley News. https://news.berkeley.edu/2018/11/06/chronically-anxious/
Nieblas-Beltrán LD, Hernández-González EA, Herrán-Arita AK (2015). Modulatory molecules involved in sleep. J Syst Integr Neurosci 2. https://doi.org/10.15761/JSIN.1000125
Walker M. P. (2009). The role of sleep in cognition and emotion. Annals of the New York Academy of Sciences, 1156, 168–197. https://doi.org/10.1111/j.1749-6632.2009.04416.x
Xie, L., Kang, H., Xu, Q., Chen, M. J., Liao, Y., Thiyagarajan, M., O'Donnell, J., Christensen, D. J., Nicholson, C., Iliff, J. J., Takano, T., Deane, R., & Nedergaard, M. (2013). Sleep drives metabolite clearance from the adult brain. Science (New York, N.Y.), 342(6156), 373–377. https://doi.org/10.1126/science.1241224