Circadian Rhythms
All species have a timing mechanism, or 'clock,' that controls periods of activity and inactivity.
These clocks are known as circadian rhythms and refer to the cycle of physiological and biological processes that fluctuate on a roughly 24-hour timetable.
Sleep / Dreaming
The altered states of consciousness that probably hold the most interest for us is sleep and dreaming. We spend a good amount of time in this altered state and many of us wish we could spend more time in it!
The EEG has allowed us to study sleep and we know that there are distinct stages of sleep based on EEG brain wave recordings. The EEG shows alpha
waves.
Sleep Stages
Stage 0: You are not asleep yet but are not awake. It is sort of the "spaced out" stage. This is the period of "falling asleep". It is also called the hypnagogic state and many times you will feel like you fell out of bed or your leg will twitch or body jerk.
Stage 1: Theta waves are emitted. Sensory images are experienced.
Stage 2: Sleep spindles are evident as well as theta waves. This stage accounts for 45-55% of sleep.
Stage 3: Beginning of delta waves. The body slows down and muscles relax.
Stage 4: Delta waves are predominant in this stage and this stage is called deep sleep. It is hard to be awoken from this stage but it is also the stage that sleepwalking can occur.
Stage 5: REM (Rapid Eye Movement) nearly all dreams occure in this stage.
Stages 1-4 are referred to as Non-REM sleep (non-rapid eye movement)
Stage 5 is REM (rapid eye movement). Beta waves are seen during REM and the brain is very active but the body becomes paralyzed.
This is called paradoxical sleep.
Can you think of a reason that the body would not be able to move during REM sleep?
The progression of these stages is called the sleep cycle and goes from stage 1 to 2 to 3 to 4 and then back to 3 to 2 and then to REM.
This sleep cycle takes about 90 minutes and is repeated between 4 to 6 times every night.
The time spent in the stages varies and REM sleep gets longer throughout the night while stages 3 and 4 get shorter.
Sleep
The reason we sleep is not entirely known but the best explanation is that sleep is restorative.
Our bodies have time to replenish and repair themselves. It also appears to be necessary in the formation of memories. Mental abilities are also reliant on a good night's sleep.
Loss of sleep results in repressed immune systems, impaired creativity and concentration, and slowed performances.
The need for sleep varies across individuals but ranges from 20 hours for an infant to 6 hours for adults in their 70's.
Dreams
One of the more fascinating parts of sleep for many is dreaming.
We all want to know what our dreams mean. Unfortunately, no one can really answer that question. Many have tried and there are hundreds of books written that try to explain dreams and their content. None have been proven right or wrong.
What we do know about dreams is that the duration of dreams ranges from a few seconds to minutes. Although you many not remember your dreams, all people do dream and they dream several times per night.
Factors that influence dream content include stress, diet, illness, and exercise. Some people experience lucid dreams where the dreamer can direct their dream. There are three theories of dreams that are considered today.
Dream Theories
Sigmund Freud believed dreams come from the unconscious and represented repressed wishes and desires. He talked about the manifest content of dreams or what the dream was. He also talked about the latent content of the dream and that is what the dream means.
There is a difference between the content of the dream and what the dream means because the content of dreams is often sexual and so it is censored by symbols that have to be explained by a psychoanalytic psychologist.
The second theory is the activation-synthesis theory. This theory states that dreams result from the brain trying to interpret meaningless, random firings and then organizing them into a story-like experience.
The third theory is the problem solving and information processing theory. This theory states that dreams are caused by people reviewing happenings that occurred when they were awake.
Sleep Disorders
There are several sleep disorders that we know about, such as insomnia or the inability to sleep that causes daytime fatigue. This has to occur for several days to weeks.
The second one is narcolepsy which is a sudden lapse into REM sleep with a loss of muscle tone.
Sleep Apnea is a third disorder that appears to be getting more common. This disorder has the sleeper briefly stop breathing during sleep and then wake and back and forth. A person suffers from fatigue since they do not get a good nights rest.
SIDS is sudden infant death syndrome and is a disorder in which a sleeping child stops breathing.
Night terrors are an intense frightening dream during stage 4 of sleep when the person can act out their dreams and possibly harm themselves.
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