Each sleep cycle involves transitions between four different stages of sleep
* NREM (Non-Rapid Eye Movement) 1, 2, and 3
* REM (Rapid Eye Movement)
Each stage involves different psychological and physical changes
Throughout the night we go through cycles approximately every 90-120 minutes
The Process
As we sleep, we transition to ‘deeper’ stages that are more internally active
NREM-3 gets shorter with every cycle
REM gets longer with every cycle
NREM-1 → NREM-2 → NREM-3 → NREM-2 → REM
NREM-1
5-10 minutes
Light sleep
When in this stage, you may feel like you’re floating, falling, or tingling
Alpha waves
NREM-2
Stable transitional stage
10-20 minutes
Harder to awaken
Theta waves
NREM-3
Deepest sleep
Hardest to awaken
Delta waves
Gets shorter throughout the night
The growth hormone is released during this phase
In this phase, the ‘body sleeps’
* All NREM’s, to an extent, are sleep for the body
* Sleepwalking and talking in one’s sleep also all occur in the NREM stages
REM
Rapid Eye Movement
Beta waves
Very internally active
Externally paralyzed
Dreams and nightmares occur in this phase
Memory synthesis
REM is like ‘sleep for the mind’
Sleep Theories
We spend roughly 1/3 of our lives asleep, but why?
Restoration Theory
Our bodies wear out during the day and use up resources
Sleep is necessary to restore these resources and reenergize the body
* Sleep helps restore and repair muscles and brain tissue
* Sleep supports growth
Adaptive Theory
Based on evolutionary approach
Sleep protects us
Sleep emerged first in animals who evolved to preserve energy
* It protects us during times where movement is not valuable and removes us from considerable danger
Sleep helped animals adapt to their environments, helping them survive, meaning the trait/behavior was passed down
Cognitive and Information Processing Theories
Sleep helps us restore and rebuild our memories of the day’s experiences
* Memory consolidation occurs during REM
Sleep deprives individuals struggle cognitively
* REM deprivation studies show this
People from all ages remember prior day’s events better with a well-rested brain
* Even rats remember how to get through a maze they learned the day before better when having slept well
Psychological Theory
Originated with psychoanalyst Sigmund Freud
* He published “The Interpretation of Dreams” in 1900 on the subject
Proposed that dreams are the road to the unconscious mind
* They’re filled with content we cannot face in conscious, waking life
Manifest and Latent content
* The literal content of the dream and the implied meaning of it
Many modern psychological theories are similar to Freud’s original theory
Biological and Information Processing Theories
Dreams provide a way to sort out the day’s events and consolidate our memories for storage
Activation-Synthesis Model
* REM helps preserve and develop neural connections
* REM triggers neural activity in the cortex as memories are synthesized
* Activation leads to synthesis
Sleep Disorders
We know that sleep restores, protects, rejuvenates, and helps us perform
But millions of people are sleep deprived, even knowing its value
Insomnia
The inability to fall or stay asleep, or both
Insomnia is the most common of all sleep disorders
Insomnia derives us not only of sleep, but of the many cognitive and physical benefits that sleep provides
Causes
Stress
Irregular sleep schedule
Pain/illness
Diet/medications
Treatment
Depends on the cause
Stress management
Medications/melatonin
Treatment of pain/illness
Changing habits
Sleep Apnea
Cessation of breathing while sleeping
Breathing stops repeatedly throughout the night
Snoring, gasping
Never feeling rested and restored even after a full night of sleep
There are three types
* Obstructive
* Central (CNS)
* Complex
Causes
Risk factors include…
Weight
Smoking
Gender
Age
A thick neck
A narrow airway
Nasal obstruction
Treatment
Depends on the cause and type
Losing weight
A C-PAP machine
Narcolepsy
Falling into uncontrollable, deep sleep all throughout the day