Sleep, Dreaming, and Circadian
Functions of Sleep:
Sleep restores your body tissues and facilitates body
Sleep increases your immunity to disease.
Sleep keeps your mind alert.
Sleep helps you process memories
Sleep enhances your mood.
How much sleep do we need?
People differ in the amount of sleep they need.
2. The older we get the less sleep we need.
Babies require between 16-18 hours of sleep a day
Preschools require 10-12 hours
Teens need 8-10 hours
Adults usually require at least 8 hours
Circadian Rhythm and our
1. If we had no cues to time, our body would exhibit a
sleep-wake cycle that approximates a 25 hour period –
this is our circadian rhythm.
2. The suprachiasmatic nucleus, a group of brain cells
in the hypothalmus, programs our circadian rhythm.
3. Our body automatically resets our biological clock
back 1 hour- from a 25 hour cycle to 24 hours every
Researchers, using electro-encephalogram
technology, have identified 5 stages of sleep.
2. They have identified two distinct sleep patterns:
non-REM sleep and REM sleep.
3. When we are awake and alert, our brain emits beta
waves, which are rapid, high frequency waves of
electrical activity in the brain.
4. When we are awake and relaxed, the brain emits
There are 4 stages of non-REM
1. Stage I sleep: a light sleep characterized by theta
waves, which are slower and less frequent than beta
or alpha waves.
Heart rate slows
Sensations often of falling or floating
Lasts from 1 to 7 minutes
2. Stage II Sleep:
Is characterized by sleep spindles, which are a pattern
of slow theta waves sporadically interrupted by burst of
Lasts approximately 20 minutes
Breathing, muscle tension, heart rate, and respiration
continue to decrease.
You are clearly asleep.
Research shows that the sleep spindles play a role in
memory processing of motor skills.
Stage III Sleep:
It is a transitional stage.
Delta waves begin. They are large, slow brain waves.
When there is a consistent pattern of delta waves, you
have entered stage IV sleep.
Stage IV Sleep:
A deep sleep
The body is extremely relaxed
Growth hormone is secreted
Body maintenance and restoration occur
It is difficult to awaken people from this stage of sleep.
If awakened, they are disoriented.
Blood flow to the brain is reduced, and respiration,
body temperature, and heart rate are slow.
After about 30 minutes of deep stage IV sleep, your brain
and body starts to speed up again, and you cycle back
through stages III and II of
non-REM sleep, then enter REM Sleep.
REM stands for “rapid eye movement” sleep.
It is a very active stage.
The heart beats irregularly
Muscle tone significantly decreases, leaving muscles
extremely relaxed and essentially paralyzed
The activity in the brain looks like you are awake!
Although we can dream throughout all stages, dreams
in REM sleep are most easily recalled. 11
A Typical Night’s Sleep:
Initially, we progress through stages I, II, III, and IV
of non-REM sleep, then reverse back through III and
II. Then we enter REM sleep.
After a brief period in REM sleep, we begin the cycle
again, starting with the non-REM stages.
One complete cycle takes about 90 minutes.
As the night progresses, we spend less time in deep
sleep and more time in REM sleep.
On average, we spend 20% of our sleep time in REM.
If you are not getting enough sleep, you will miss out
on the longest period of REM sleep at the end of the
Why Do We Dream?
1.Freud called dreams “the royal road to the
unconscious” in his book, The Interpretation of
According to Freud, dreams allow us to express
repressed fears, sexual desires, and aggressive feelings
without the censorship of our conscious thought
He suggested that dreams contain both manifest
content and latent content.
Another theory about dreaming is
the Threat Simulation Theory:
It posits an evolutionary function of dreams. Suggests
that dreams are an ancient biological defense
mechanism, that allows us to repeatedly stimulate
potentially threatening situations, so we can rehearse
our responses to the events.
This theory explains the nightmares experienced by
persons who have experienced childhood trauma.
The Activation Synthesis Theory:
The theory suggests that dreaming is just the result of an
aroused brain during REM sleep, when the brain
shows activation of millions of random neural
impulses. The cortex tries to create meaning out of the
random firings by synthesizing them into familiar
images or stories based on our stored memories. These
stories may reflect:
Information accessed during waking
This theory about dreaming suggests that dreams are a
form of mental house-keeping.
The dreams are a way of consolidating information
and paring off trivial details– in this way they are a
function of memory.
The Continuity Hypothesis:
This theory says that dreams are a way of coping with
daily problems and events.
It suggests that we dream about everyday experiences
and concerns in an effort to resolve difficulties and