Body Rhythms and Sleep
Outline
• Biological Rhythms
• Shifting Biological Rhythms
• Sleep: Forms and Physiology
• Sleep Disorders
• Dreams
Understanding Biological Rhythms
• Biological rhythms
– A periodic, more or less regular fluctuation in a
biological system; may or may not have
psychological implications
• Entrainment
– Biological rhythms are synchronized with
external events such as changes in clock time,
temperature, and daylight
Endogenous Biological Rhythms
• Circadian Rhythms
•
•
– Occur about every 24 hours
– Example: The sleep-wake cycle
Infradian Rhythms
– Occur less often than once a day
– Examples: birds migrating, bears hibernating
Ultradian Rhythms
– Occur more frequently than once a day, about
every 90min
– Examples: stomach contractions and hormone
levels
Circadian Rhythms
• Circadian rhythms are cycles of activity and
inactivity generally lasting about one day
(from the Latin circa = “about” and dies =
“day”.)
• Most people’s circadian rhythms, when
allowed to occur in an environment free of
familiar time cues, stabilize at a little over 24
hours.
Circadian Rhythms
• Your degree of alertness depends where
you are in your circadian rhythm.
• Are you are morning person or an evening
person?
– Most young adults are evening people, or
neutral.
– Most people over the age of 65 are morning
people.
Brain mechanisms
• The circadian cycle of sleep and wakeful states
is governed by the suprachiasmatic nucleus
(“SCN”.)
• This tiny structure at the base of the brain is
essentially your body’s “clock.”
Circadian Rhythms
• Suprachiasmatic nucleus (SCN)
– Influenced by external light and sends messages
to the pineal gland to cease secreting melatonin.
• Melatonin is produced during the night and
falls during the day
Infradian Rhythms and Mood
• Seasonal Affective Disorder (SAD)
– A controversial disorder in which person
experiences depression during the winter
and an improvement of mood in the
spring
– Treatment involves phototherapy or
exposure to fluorescent light
– Evaluating frequency of and treatment for
SAD is difficult
Menstrual Cycles and Mood
• Question: Who believes the menstrual cycle
influences women’s mood?
• Physical symptoms are common
• Emotional symptoms are rare
– Irritability and depression
– Fewer than 5% of women have
symptoms predictably
Research Conclusions about “PMS”
• No gender differences
•
•
•
exist in mood
There is no relation
between stage of
menstrual cycle and
emotional symptoms
No consistent “PMS”
pattern exists across
menstrual cycles
No connection exists
between “PMS” and
behaviour
Why Women Overestimate “PMS”
• They notice depression or irritability when
these moods occur premenstrually but
overlook times when moods are absent
premenstrually
• They attribute irritability before menstruation
to PMS and attribute irritability at other times
to other reasons
• They are influenced by culture and myths
about PMS
• CONFIRMATION BIAS
Concept Check: Matching
• Ultradian Rhythms
• 24-hour cycle
• Circadian Rhythms
• Long-term cycle
(months)
• Infradian Rhythms
• Short-term cycle
(approx. 90 minutes)
Concept Check
• What is the name of the structure that
controls sleep and wake cycles?
___________
• What hormone influences how sleepy you
are? ___________
Desynchronization
• Under normal conditions, our body’s rhythms
are governed by the SCN
– Rhythms are synchronized with external and
internal events
• However, internal desynchronization can
occur, especially when people take airplane
flights across several time zones.
Shifting sleep schedules
• Mechanisms in the brain
rely on light to reset your
body’s clock and keep it in
step with the
environment.
• If you travel between time
zones, the light in your
new location will
eventually reset your
clock, but you will be out
of step for a while.
Shifting sleep schedules
• Jet lag is the period of
weariness and discomfort
that occurs while your
body clock is out of step
with your new time zone.
It is easier to adjust going
east to west than west to
east.
•Jet lag affects energy level, mental skills,
and motor coordination.
Study: Flight Attendants
• Flight attendants had
– higher concentrations of the stress hormone
cortisol in their saliva
– lower scores on visual memory tests
• Prolonged and excessive
cortisol levels
– can result in neural death
• memory deficits
Recovery from Jet Lag
• Use bright lights to “reset” the clock in the
SCN,
– fool the brain into a new schedule.
• Small amounts of melatonin on a
controlled schedule
• Sleep when the flight attendants tell you
to sleep…
Shifting Sleep Schedules
• Internal desynchronization also occurs when
workers must adjust to a new shift.
– Decreases in efficiency
– Irritability and increased likelihood of accidents
Dangers of Shift Work
• Examples of shift work: police officers,
emergency-room personnel, airline pilots, truck
drivers, and operators of nuclear power plants
– Some famous accidents associated with internal
desynchronization:
• the 1989 Exxon Valdez oil spill off the coast of
Alaska
• Three Mile Island and Chernobyl nuclear power
plant meltdowns
Daylight Savings Time
• Spring shift to Daylight Savings Time (and the
1 hr of sleep deprivation) led to a short-term
increase of the likelihood of accidental death
(Coren et al.)
Measured over
3 years.
Concept Check
If you are a Vancouver based CEO, and you
need meet with an executive from India to
negotiate a tough deal, should you try to
meet the executive in Europe or in Japan?
Why We Sleep
• The exact function of sleep is uncertain but
sleep appears to provide time for:
– the body to eliminate waste products from
muscles
– repair cells
– strengthen the immune system, and
– recover abilities lost during the day
• This is referred to as the restorative theory of
sleep.
Evolution and Sleep
• The evolutionary theory: evolution has
equipped all animals with a regular pattern of
sleep and wakefulness to help us conserve
energy and avoid dangers.
• This theory accounts well for differences
among species.
Different Sleep Patterns…
• Lions sleep about 20 hours a day while
gazelles sleep much less. Why?
Measuring Stages of Sleep
• Polysomnography is a
comprehensive recording
of the physiological
changes that occur
during sleep
– EEG brain activity
– EOG eye movements
– EMG muscle activity
– ECG heart rhythm
– Breathing function is also
measured
Stages of Sleep
• There are
multiple stages
of sleep, each
with a distinct
pattern of
brainwaves.
Alpha Waves - Awake
• Initial (eyes closed): your brain emits bursts of
alpha waves.
• On an EEG recording, alpha waves have a regular,
•
slow rhythm and a high amplitude (height).
Gradually, these waves slow down even further,
and you drift off to sleep
Stage 1 Sleep
• When first dozing off, the sleeper enters
Stage 1.
– Gateway between awake and sleep, “drowsy
sleep”
– Loss of muscle tone and conscious awareness of
external environment
– Light sleep, little eye movement, and a fair
amount of brain activity (“desynchronized”
activity).
Stage 2 Sleep
• Stage 2: a gradual transition begins into the
synchronized, slow wave states.
– conscious awareness of external environment is
gone
– Less muscle activity; breathing and heart rate slows
– 45-55% of total sleep time
Stage 3 Sleep
• Stage 3 is a transition into stage 4
– The sleeper gradually moves back through
stages 3 and 2 and then has the first brief REM
episode of the night.
– only 3-8% of total sleep time
– Long, slow delta waves
Stage 4 Sleep
• Stage 4 predominates in the first 3rd of the
night and accounts for 10-15% of total sleep
time.
– Almost entirely delta waves
– Deepest stage of sleep – hard to wake someone
up in this stage
– Night terrors and sleepwalking occur in this
stage
Rapid Eye Movement
(REM) Sleep
• Stage 5, or REM sleep
– It is also referred to as paradoxical sleep because
there is physiological and brain wave activity
almost indistinguishable from the waking state.
Yet the large muscles of the sleeper are so relaxed
that the person is effectively paralyzed.
– Associated with dreaming
– More predominant in last 3rd of night
– Brain activity looks like that of Stage 1
The Functions of REM Sleep
• New research suggests that REM sleep may
help to improve memory for difficult new
tasks.
– Students who sleep between learning and the test
score higher on memory tests.
• People deprived of REM sleep become quite
irritable, anxious and distracted.
– There is a “rebound” when finally allowed to
indulge (more than usual amount of REM).
Stages of Sleep
Rhythms of Sleep
• Ultradian cycle that recurs ~ 90 minutes
– Nap for 20 or 90 minutes, not 60
• 60 minutes is when deep sleep occurs…groggy
• The REM periods last from a few minutes to
as long as an hour, averaging about 20
minutes in length.
– EEG during REM is similar to alert wakefulness
Typical Night’s Sleep for a Young Adult
Concept Check: True or False
• Alpha waves are associated with being
awake.
• Delta waves are associated with Stage 2
sleep.
• The muscles are paralyzed during REM
sleep.
• The rhythms occurring during sleep are
infradian rhythms.
We need to sleep
• Sleep is necessary for normal mental
functioning.
– After the loss of even a single night’s sleep,
mental flexibility, attention, and creativity are
reduced
– Chronic sleep deprivation=high levels of cortisol
• Impairs memory
• Hallucinations and delusions
• The amount of sleep varies from person to
person (not necessarily 8 hours)
Sleep Disorders: Insomnia
• Insomnia—difficulty in falling or staying
asleep.
• Many adults have occasional insomnia.
• It can be caused by a number of factors:
– Psychological problems (depression and
anxiety)
– Physical problems such as arthritis
– Irregular or overly demanding work and
study schedules.
Sleep Disorders: Sleep
Apnea
• Sleep apnea–breathing periodically stops for a few
moments
– Snoring is closely associated with this disorder.
Many sufferers from sleep apnea are obese men
who are usually middle-aged or elderly.
– Two causes:
• Abnormalities in the medulla (brainstem),
resulting in no signals for the lungs to breath
(uncommon)
• Efforts to breath continue, but a physical
obstruction blocks air flow for a few moments
(more common)
Sleep Disorders: Narcolepsy
• Irresistible and unpredictable daytime attacks of
sleepiness lasting from 5 to 30 minutes.
– 27,000 Canadians suffer from this condition,
many without knowing it.
– The cause may involve the degeneration of a
particular set of neurons in the hypothalamus
– genetic factors seem to be involved
Abnormalities of Sleep
• Parasomnias – other unsettling occurrences
during sleep include:
– Sleep talking, which is not a symptom of any
mental or emotional disorder.
– Sleep walking, usually found in children during
stage 4 sleep. It is not the case that “you should
never wake a sleepwalker.”
– Night terrors, which involve awaking during slowwave sleep in an extreme panic. These are common
in children, less so in adults.
Sleep Deprivation: ‘normal’ causes
• Most common cause of sleepiness is—staying up
late and not allowing yourself to get enough
sleep at night.
• Two-thirds of all North Americans get fewer than
•
the recommended eight hours.
– Students get only about six hours of sleep a
night on average
Most people need at least eight or nine hours…
Sleep Aids
• Melatonin seems to promote sleep directly.
– have been used to treat insomnia…mixed results
• Benzodiazepines (reduce anxiety)
• Increase GABA release
– Inhibitory neurotransmitter
“Sleep Hygiene”
(Zarcone & Stepanski, 2000)
• Reduce time spent in bed when not sleeping,
•
•
•
particularly if feeling frustrated or worried about
difficulty falling asleep.
Leave the bed if having difficulty falling asleep and
engage in a relaxing, distractive activity, such as
reading or watching television.
Establish and maintain a regular sleep-wake cycle.
Engage in moderate exercise daily but avoid
exercising right before bedtime.
“Sleep Hygiene”
• Establish a calm, quite bedroom setting. Remove the
•
•
•
•
bedroom clock from view at night.
Ensure a comfortable bedroom temperature.
Have a light snack before bed, but avoid excessive
fluid intake.
Limit consumption of nicotine, caffeine, and alcohol,
particularly before bedtime.
Use sleep aids only occasionally.
Concept Check: Matching
• 1) Sleep Apnea • A) Awaking during slow-wave
• 2) Insomnia
•
• 3) Night terrors •
• 4) Narcolepsy
•
sleep in extreme panic
B) When breathing periodically
stops during sleep
C) Frequently and
unpredictably falling asleep
during the day
D) Difficulty getting to sleep or
staying asleep
REM and Dreaming
• Dreaming involves an involuntary
conjuring up of images in a sequence in
which the sleeper/dreamer is usually more
a participant than an observer.
– Generally occurs during REM sleep
– Can also occur during Stage 2
The Content of Our Dreams
• It was once believed that dreams foretold
the future.
• But we now are certain that this is only by
coincidence.
• The major controversy in psychology is
whether or not the dream tells us
anything about the dreamer.
• This is far from settled.
4 Theories of Dreams and Dreaming
• Dreams as unconscious wishes
• Dreams as reflections of current concerns
• Dreams as by-products of mental
housekeeping
• Dreams as reflections of brain activity
Dreams as Unconscious Wishes
• Sigmund Freud concluded that our
nighttime fantasies provide insight into
desires, motives, and conflicts of which we
are unaware—a “royal road to the
unconscious.”
– dreams express wishes and desires that have
been forced into the unconscious part of the
mind.
Dreams as Unconscious Wishes
• Freudian
interpretation: every
dream is meaningful,
no matter how
absurd the images
might seem.
Freudian Dream Interpretation
• Two types of content in dreams:
• Manifest content
– Dream content that we consciously
experience during sleep and may remember
upon wakening,
• Latent (hidden) content
– unconscious wishes and thoughts being
expressed symbolically.
• Problem: There are no concrete rules for
interpreting dreams…confirmation bias!!!
Dreams as Reflections of Current
Concerns
• Dreams reflect conscious preoccupations of
daily concerns
– Including relationships, work, sex, or health
– symbols in a dream do not disguise
meaning; they convey it.
• Supported by findings that dreams are more
likely to contain material related to a person’s
current concerns than chance would predict.
– e.g., test-anxiety dreams in students
Dreams as By-Products of Mental
Housekeeping
• Unnecessary neural
•
•
connections are eliminated
and important ones are
strengthened
The brain divides new
information into “wanted”
and “unwanted”
What we recall as dreams
are only brief snippets from
scanning and sorting that
occurs during REM sleep
Dreams as Interpreted Brain Activity
• Activation-synthesis theory
– Dreaming results from the cortical synthesis and
interpretation of neural signals triggered by activity
in the pons (brainstem)
• Pons: sleep, eye movements, posture
– No psychological meaning to pons firing
– At same time, brain regions that handle logical
thought and sensation from the external world shut
down
Activation Synthesis Theory
Concept Check
Are dreams less likely to be reported
towards the beginning or the end of the
night?
According to the activation-synthesis theory of
dreams, which brain area sends out signals that
are interpreted by the rest of the brain?