Biological Rhythms
What are Body Rhythms?
• Body rhythms are biological processes that show
cyclical variation over time…ranging from hours
to years and reflect the influence of the earths
rotation upon us… it's living inhabitants, along
with plants and animals.
• There are three rhythms that we will focus our
attention upon throughout this module.
• Circadian Infradian, and ultradian biological
rhythms.
Body Rhythms (cont’d)…
• Circadian rhythms:
(circa = approx and diem = day) go over 24hrs. Humans
demonstrate a series of changes including temperature
heart respiration and metabolism over this period. We
(psychologists) are most interested in the sleep-wake
cycle.
• Ultradian rhythms:
(Meaning less than one day) Sleep is a good example of
an ultradian rhythm, as you sleep you pass through
differing stages of sleep (e.g. light and deep sleep lasting
about 90 minutes.)
Body Rhythms (cont’d)…
• Infradian rhythm: (meaning more than 1
day). An example of a infradian rhythm
would be a woman's menstrual cycle which
lasts for 28 days.
• A circannial cycle occurs yearly/annually.
An example of this would be non human
animals hibernation and waking patterns.
Research Studies into Circadian
Rhythms.
• If bodily rhythms show a similar daily
pattern for people with different lifestyles it
would seem these rhythms are ‘part of our
nature’ and not our ‘upbringing or
nurture’
• So..the next question would be is whether they are
natural and triggered internally or whether they
rely upon external cues in the environment.
Research Studies into Circadian
Rhythms.
• Siffre (1975) Spent 6 months inside a cave and found
that his natural Circadian rhythm was just over 24 hr,
but would sometimes change to 48 hr.
• There were no zeitgebers such as natural light or
sounds. He had no idea what time it was, although he
did have contact with outside world via telephone. He
had food and drink and so on. His behaviour such as
when he slept/woke and when he ate his meals was
monitored. From this study it was concluded our
internal clock must have a 25-hr cycle and that our
zeitgebers must reset the clock to our usual 24-hr day.
Research Studies into Circadian
Rhythms…
• Another way to test circadian rhythms is to alter
our environmental cues.
• Folkard (1985) 12 participants lived in ‘temporal
isolation’ for 3 weeks…isolated from natural light
and other time cues. They agreed to go to bed at
11.45 pm and get up when it said 7.45 am. The
clock initially ran to time but gradually quickened
until it indicated a passing of 24 hr for 22 hr. All
but 1 of the participants kept pace with the
clock…thus demonstrating a strong free-running
rhythm.
Evaluation of Research Studies into
Circadian Rhythms…
• Participants were isolated from exogenous cues
(environmental) and we know these have an effect
upon our circadian rhythms….but were not
isolated from artificial light...it is now known
these too can have an effect!!
• Individual differences- Are you a morning or
evening person?
• Duffy et al (2000) found early risers prefer 6 am10 pm cycles and late starters prefer
10
am - 1 am cycles.
Evaluation of Research Studies into
Circadian Rhythms…
• What everyday application could we gain
from studies such as these…(how useful is
this stuff really???)
• Deciding the best time to study.
• Taking medication for serious medical
conditions. (chronotherapeutics)
Research studies into infradian rhythms.
• Monthly cycles...the function of this cycle is to
regulate ovulation.
Research Studies into Infradian
Rhythms.
• Seasonal Affective Disorder (SAD). Research
has shown that the hormone melatonin is
secreted when it is dark...the more
darkness...the more melatonin. This leads to
severe disruption in mood.
Evaluation of Studies into Infradian
Rhythms.
• Menstrual cycles can also be disrupted by other
factors as well as hormones...research has shown that
when a several women live in a house together and
they are not taking oral contraceptives they tend to fall
in line with each other and menstruate at the same
time this be possibly due to pheromones being
released chemically and giving a scent.
• SAD a greater understanding of this condition has lead
to successful therapies such as phototherapy- very
strong lights to increase the level of melatonin.
Research Studies into Ultradian Rhythms
• These are rhythmic cycles with a period of less than one
day. Examples include levels of alertness throughout the
day and the cycle of brain activity during sleep.
• NREM and REM: There are 4 stages (1 & 2) which are
shallow into deep sleep/slow wave sleep (3 & 4). These
cycles continue throughout the night with (SWS)
becoming shorter and REM becoming longer as the night
progresses. Cycles last for approx 60 min in early infancy
and 90 min in adolescence.
• The use of an electroencephalogram (EEG) can show the
electrical activity of the brain. There are different patterns
of activity at different times during sleep (Rechtschaffen
& Kales, 1968).
Circadian Rhythms
• Circadian = diurnal + nocturnal
• Zeitgebers and the SCN: Biological clock
– Altering light/dark cycles produces phase shift
and entrainment
Suprachiasmatic Nucleus (SCN)
SCN - main control center
for sleep and temperature
circadian rhythms
What sets the Clock?
Zeitgeber: a stimulus that resets the biological clock (e.g. bright
light, exercise, temperature)
Evidence for the SCN as biological clock
–
–
–
–
–
Free-running rhythms and the 24+ hour period
SCN lesions disrupt circadian rhythms
SCN tissue maintained in vitro retains cyclicity
Transplanted SCNs set rhythms of donor animal
Recall the pathway in the visual system from
retina to SCN: These retinal ganglion cells
contain a photopigment, melanopsin, and are
light sensitive
The Role of Endogenous Pacemakers and
Exogenous Zeitgebers.
• The main pacemaker for endogenous (internal) rhythms is
the suprachiasmatic nucleus (SCN). This is a small group
of cells located in the area of the brain called the
hypothalamus. Its called the SCN because it lies just
above the optic chiasm, therefore it can receive
information directly from the eye and the rhythm can be
rest by the amount of light entering the eye.
The Role of Endogenous Pacemakers and
Exogenous Zeitgebers (cont’d)….
•
The way the SCN works is as follows:
This rhythm
then affects
the sleep wake
cycle via the
pineal gland.
Production of protein for number
of hours
The level inhibits further production,
again for a number of hours.
The protein drops another level
Stimulation of
the pineal gland
produces the
hormone
melatonin
(sleepy) When
light levels are
low we produce
more melatonin..
and the SCN starts producing the protein again.
The Role of Endogenous Pacemakers and
Exogenous Zeitgebers (cont’d)….
• So what about exogenous (external) pacemakers???
• Light is considered to be the most dominant zeitgeber.
(see..Miles et al 1977)
• Opposing research also indicates that there are other
factors that should be taken into consideration
(see..Luce & Segal 1966)
• Overall it appears the sleep-wake cycle is strongly
dictated by endogenous pacemakers but we can
override these cues.
• It what circumstances might this happen?
The Role of Endogenous Pacemakers and
Exogenous Zeitgebers Evaluation…
• It is adaptive for endogenous rhythms to be rest by external
cues so that animals are in tune with seasonal variations and
day/night time. This idea of adaptive ness comes from
evolutionary perspective that refers to the idea that behaviours
which persist are more likely to promote ones survival.
• It could be life threatening if we relied solely upon external
cues, therefore we must not forget the significance of internal
cues.
Optic nerve
Pathways to SCN
Optic chiasm
Optic tract
Lateral geniculate nucleus
Optic radiation
Primary visual cortex
Circadian Physiology
Circadian Rhythms
• endogenous cycles
• role of the suprachiasmatic nucleus
• setting/resetting biological clocks
Sleep
• why sleep?
• stages of sleep
Dreaming
• why dream?
Circadian Rhythms
Endogenous circadian rhythms
• rhythms that last about a day
• humans’ last around 24.2 h
Examples:
-activity
-temperature
-waking and sleeping
-secretion of hormones
-eating and drinking
What Resets the Clock?
Light
• retinal ganglion cells send direct projections to the SCN
• this provides information about light to the SCN
Melatonin
• secreted from the pineal gland
• increased levels of melatonin make you sleepy
• melatonin can act on receptors in the SCN to phase-advance the
biological clock
Sleep
Neural Control of Sleep
• Is sleep a passive process?
– The cerveau isole’ of Bremer (1936): SWS only
– The encephale isole’ and the RAS: normal sleep
– Partial transections leaving the RAS intact
• Ventrolateral Preoptic Area (VPA) triggers
sleepiness and slow-wave sleep
• Warming the basal forebrain induces slow-wave
sleep: GABA on tuberomammillary nucl.
• VPA receives input from thermoreceptors
More Neural Control
• PGO waves in the EEG from implanted
electrodes
• Executive in the dorsolateral pons, called the
peribrachial area.
• Kainic acid lesions of peribrachial area reduce
REM sleep
• Carbachol, an ACh agonist, in ventral pons
(medial pontine reticular formation) triggers
REM phenomena.
The Sleep Cycle
• Electronic recording: EEG, EOG, EMG
• EEG patterns divide sleep into four stages:
– 1: a waves, 8 - 12 Hz, low amplitude, moderate
frequency, similar to drowsy wakefulness
– 2: slower frequency, higher amplitude, plus
• K complexes
• Sleep spindles
– 3: d waves appear, 1-2 Hz, large amplitude
– 4: Dominated by d waves
EEG patterns
b
a
2k
3d
1 sec
EEG patterns...
4d
1 sec
REM sleep phenomena
• Stage 1 EEG: Paradoxical sleep
• EOG (and corneal bulge) show frequent eye
movements, as if scanning a visual field.
• EMG shows loss of muscle tonus due to
downward inhibition of a motor neurons,
although muscles moving hands and feet
may twitch.
• Many brain structures function as if awake.
More REM phenomena
• SNS is partially activated: Increases blood
pressure, respiration, and heart rate.
• Genital response
• Narrative dreaming
– CBF is high to visual cortex, low to inferior frontal
cortex (Madsen, 1991)
– Eye movements match dream events
– One EEG waveform is unique to REM and wakeful
scanning
Sleep: Stages
A Typical Night
After 11 days of total sleep
deprivation
Research studies into Ultradian rhythms….
Effects of sleep deprivation
• Sleep deprivation within a circadian cycle is
followed by less sleep, not more
• Internal desynchronization: free-running
body temperature cycle and sleep-wake
cycle may desynchronize.
So, what goes on in the brain in
SWS?
• Areas that  arousal  shut down.
• Primary sensory areas also shut down.
• Areas involved in memory consolidation
and retrieval don’t shut down, but are
isolated from sensory input.
So, what goes on in the brain in
REM?
• INCREASE in sensory integration,
motor, limbic, and memory areas.
– Why don’t we move, if motor areas are
activated?
• One brain area sends inhibitory input to
the spinal cord to prevent movement.
• Frontal cortex shuts down, disinhibiting
limbic system.
Reticular formation (red) wakes the brain.
Locus coeruleus (blue) inhibits muscles.
Basal forebrain (yellow)  SWS.
Why Sleep?
Repair and Restoration Theory
– Sleep enables the body and brain to repair itself after
working hard all day
– Brain is ~3% of total body weight, but uses almost ¼ of the
energy.
– Going without sleep causes people to be irritable, dizzy, and
to have hallucinations and impaired concentration
– Sleep-deprived rats’ bodies work harder
– BUT, how much we sleep does not depend on how much
we worked that day
Who sleeps?
• Mammals and birds
– Opossums, sloths, bats: 19-20 hours daily
– Cats, dogs, rodents: 12-15 hours daily
– Ruminant herbivores: 2-3 hours daily
• Reptiles, amphibians, fish, and insects have
cycles of inactivity
• Note that sleep time does not correlate with
waking activity levels, but does relate to
waking vulnerability.
Why Sleep?
Evolutionary Theory
- we evolved to sleep so that we would
conserve energy when we were least
efficient
- during sleep body temperature
decreases
- predicts that species will sleep different
amounts depending on how much they
must look for food and watch for
predators
Dream research
• External stimuli may be incorporated into a
dream.
• Dream events happen in real time.
• Everyone dreams; recall depends on when
in the sleep cycle you awaken.
• Genital response is independent of dream
content.
• Sleep-walking and talking are non-REM.
Interpretation of dreams
• Manifest content is symbolic of latent
desires (Freud)
• Activation-synthesis theory: cf.
incorporation of external events into
dreams.
• Lucid dreams: Have you had one?
Why Dream?
Facilitate problem solving ?
Facilitate memory consolidation ?
• Lots of REM sleep predicts better consolidation of emotional
information.
•Lots of SWS predicts better consolidation of motor tasks.
•Lots of SWS+REM predicts better consolidation of perceptual
information.
• Patterns of activation of hippocampal neurons are repeated
Sleep Disorders
• Waking phase disorders
– Insomnia
• Drug-dependency insomnia
• Sleep apnea: PAP or surgery
• Fatal familial insomnia: thalamus damage
– Reduction of sleep spindles and K-complexes
• SIDS
– Narcolepsy
• Cataplexy
• Decreased hypocretin neurons
– Sleep paralysis
– Hypnagogic hallucinations
More sleep disorders: Sleeping
phases
• REM sleep behavior disorder
• Slow-wave sleep problems
– Nocturnal enuresis
– Somnambulism
– Pavor nocturnus (Night terrors)
Overall sleep deprivation
• Under total, voluntary sleep deprivation,
sleepiness is cyclical
– Greatest sleepiness from 3-6 a.m.
– Waking sleepiness is countered by activity
– Sleepiness increases only up to four days
• Active, complex tasks are not impaired
• Easy, boring tasks are impaired
• Microsleep emerges
Compensation for sleep deprivation
• Subsequent slow-wave, non-REM sleep is
increased
• Stage 3 and 4 sleep is almost completely
restored
• Involuntary sleep deprivation is stressful
– Executive rats on a carousel apparatus died
– Post-mortem exams showed few of the usual
stress symptoms
REM deprivation
•
•
•
•
REM pressure
REM rebound
REM escape
Three theoretical effects
–
–
–
–
Mental disorder
Amotivational syndrome
Memory processing deficits
But tricyclic antidepressants block REM with none
of these side effects.
Sleep Deprivation as a Stressor
• Hypothalamic corticotropin INHIBITING factor (CIF)
 SWS
• ~ I hr before waking: CRH, ACTH, and GCs rise and
 waking.
• If you don’t get enough sleep: decline in stress
hormones doesn’t occur.
– In fact, stress hormones increase.
• If sleep-deprived, frontal cortex and other areas work
overtime:
– “a bunch of unshaven gibbering neurons counting
on their toes, having to ask the rest of their cortical
buddies to help out with this tough math
problem.””
Sleep Deprivation as a Stressor
• Airline flight attendants: 5 vs. 15 days
between transcontinental flights.
– Attendants for airline with 5 day interval
had smaller temporal lobes, impaired
explicit memory, higher GCs.
Stress as a Disruptor of Sleep
• CRH suppresses sleep
–
–
–
–
“throws ice water on those happily dozing neurons”
Direct effect on neurons
Also via SNS
Inhibits mostly SWS, which is needed more than more
shallow stages.
– GCs impair memory consolidation.
• Random wakening  higher CGs than predictable
awakening:
– “a sleeping brain is still a working brain.”
Resynchronization
• Jet lag and shift work
• Phase shift: Delay is better than advance
–
–
–
–
Morning melatonin phase-delays
Afternoon melatonin phase-advances
Evening melatonin is ineffective
Bright light exposure has the opposite effects
• Strengthen zeitgebers like light and activity
early in the new waking period
The Consequences of Disrupting
Biological Rhythms.
• When external cues change we have to readjust our internal clock…….
• JET LAG
SHIFT WORK.
Shift Work…..
• Rising early or retiring to bed earlier than
normal is an example of phase advance.
• Going to bed late or getting up late is an
example of phase delay.
• By delaying/advancing our rhythms we are
compromising our ability to cope in the
short term.
• On average it takes approx 3 days to adjust
to a 12 hour shift in time.
Shift Work…..
• We need doctors, nurses, policeman etc..so
how do they cope?
• What happens to their cycle when it is
disrupted by shift work?
• Well…we know what sometimes happens
when they do work shifts..accidents!
• Lets look more closely at the facts!!
Shift Work…..The Facts!!
• Chernobyl occurred between 1am & 4am.
• Most lorry accidents occur between 4am & 7am.
• In the US $77billion annually as a result of accidents and
ongoing medical expenses due to shift work related
illnesses.
• Therefore research in this area has important implications.
• Evidence: Hawkins and Armstrong-Esther(1978) studied
11 nurses during a 7 night rotation of their duty.
Performance was significantly impaired on the first night
but improved through the week. (Temps did not adjust
until last night!)
Shift Work…How can we reduce the
impact/effects of shift work?
• Monk and Folkard (1983) identified two major
types of shift work:
• (a) Rapidly rotating shifts: One/two shifts max
then they move to different time.
• (b) Slow rotating shifts: Rotate shifts on a
weekly/monthly basis.
• Q: Which is the lesser of two evils??
• A: Rapidly rotating….at least they allow the
worker to maintain a fairly constant circadian
rhythm.
Shift Work…How can we reduce the
impact/effects of shift work?
• Rapid rotation means your rhythms are constantly
disrupted.
• Research has shown that it is possible to reset the
internal clock by using bright lights as a substitute
for sunlight.
• What will this reset?
• Dawson and Campbell (1991) exposed workers to
a 4 hr pulse of very bright light. This appeared to
work!
Shift Work…How can we reduce the
impact/effects of shift work?
• Phase delay might also be more beneficial..
• Early
Late
• Late
Early
It is better
to rotate
with the
clock than
against it.
• Evidence: Czeisler et al (1982) tested phase delay.
Workers in a chemical plant in Utah found phase delay
made them feel better. The management also reported
increased productivity and fewer errors.
Jet Lag….The Facts.
Jet Lag only
occurs when flying
from East-West
or from West to
East.
in other words
when we change
time zones.
Jet Lag does not
occur form NorthSouth and vice
versa!!
Example
You fly from
Scotland –Boston
(USA). You leave at
11am arrive 5pm
British time
actually it is 12pm
in Boston...by 8pm
Boston time you’ll
be tired as it is
1am to you
normally!!
Jet Lag….The Facts.
• Klein et al (1972) found that adjustment
was faster for westbound flights (going to
states) than eastbound ones regardless of
whether you were travelling home or going
away.
• Eastbound = re-adjustment took 1 day per
time zone crossed, therefore how long
would it take to recover from a flight to
Britain from Boston
Jet Lag….
• Its easier to adapt to jet lag when flying in a
westerly direction because the day of travel is
lengthen, whereas it is shortened when travelling
east!
• As our endogenous cycle is about 25 hours we are
more able to cope with phase delay than phase
advance.
• Huh??? We can stay up when we should be a sleep
but we don’t like being woken we want to sleep!
Jet Lag….
• Evidence
Schwartz et al (1995) found that east coast US
baseball teams did better when travelling West
(phase delay) than West coast teams who
travelled East (phase advance). The time
difference was 3 hours. This would give the
East coast an advantage!!
• But what could be a possible problem with this
evidence?
Jet Lag…How can we reduce the
impact/effects of Jet Lag?
• Use melatonin to reset the body clock..
• Should not be used unless intending to stay in new time zone
over 3 days.
• Cabin crew tend to do overnight east-west then 24hrs on
ground and west-east...taking melatonin in these cases may
not be advisable.
• Timing is important too...individuals should be allowed to
sleep after the melatonin or else they are prolonging their
circadian rhythm.
• There is little scientific evidence on flying performance and
melatonin however….cabin crew who have ingested
melatonin are not allowed to fly within 36 hr ????
• Adopt local eating times etc to help reset the biological
clock as soon as possible.
The Per-Cry-Tau complex
• In mammals, two SCN proteins (Clock and Cycle) form a
dimer.
• The Clock/Cycle dimer acts on DNA to enhance
transcription of Period (Per) and Cryptochrome (Cry).
• Per and Cry bind in a complex with Tau
• The Per-Cry-Tau complex inhibits the Clock/Cycle dimer,
slowing Per-Cry production
• Per-Cry breakdown over 24 hours allows a new cycle to
start.
• Melanopsin-containing ganglion cells release glutamate in
the SCN, increasing per transcription and entraining the
SCN.
Genetic variations
• Variations in the Clock gene may
distinguish morning people from evening
people
• Fatal familial insomnia is caused by a dual
mutation involving a prion gene PrP.
– Found in 40 families worldwide
– Mean onset: age 50
– Death ensues 7 to 36 months later.
Summary
• SCN is “biological clock”
• A “Zeitgeber” is a regular stimulus that entrains the
circadian rhythm.
• 90-minute cycles of 4 stages of SWS (1 through 4
and back) plus REM.
• Sleep deprivation  increases in stages 3 & 4 and
REM on subsequent nights.
• The reticular formation in brain stem  waking.
• Locus coeruleus inhibits spinal motor neurons
• Basal forebrain  SWS
Summary
• Memory consolidation occurs during sleep
– Emotional memories during REM
– Motor memories during SWS
– Perceptual memories during both SWS and REM
• Corticotropin INHIBITING factor (CIF) may  SWS
• CRH decreases sleep
• Sleep deprivation  increased GCs and
INCREASES cortical activity (inefficient).