Introduction into rhythms
A biological rhythm is a cyclical variation over some period of time in psychological or physiological processes (Gross Mcllveen) Rhythms are repeated over different interval influenced by endogenous and exogenous factors
different types of rhythms:
Ultradian- rhythms that recur less than 24 hours such as sleep stages
Circadian- rhythms that recur every 24 hours such as your sleep wake cycle
Infradian - rhythms that recu more than 24 hours such as the menstrual cycle
Circadian rhythms 1
Rsearch into circadian rhythms:
Aschoff and Wever
- one of the 1st to research the importance of exogenous zeitgebers on our cicadian rhythms
- took place in munich
- participants isolated in world war two bunker
- were able to turn arteficial lights on and off at own will
- had no other external cues on whether day or night
- FINDINGS- PARTICIPANTS FOLLOWED A 25 HOUR SLEEP WAKE CYCLE
Circadian rhythms 2
- chronobiologist- looked in human biological clock
- he was the sole participant in numerous studies
- 1962-cave in alps for 2months -thought it was the 20th aug when came out but was actually 17th sep-
- 1972- midnight cave in texas for 205 days
- 1999- underground for 3 months
- FINDINGS= A 25 HOUR CYCLE FOR ALL
EVALUATION OF CIRCADIAN RHYTHMS
- INCONSISTANT results - findings have varied hugely in terms of the sleep wake cycle , varying from 13-65 however there has been a fairly consistant finding of 25 hours
- SAMPLE SMALL- most research into circadian rhythms has been done using case studies or using a small sample such as siffre therefore we cannot generalise to the wider population. and therefore lacks ecological validity. could have been individual differances that accounted for such results
- STRICTOR CONTROL NEEDED- czeisler et al claimed that isolating particpants behaviour without strict control was unsufficient to reveal endogenous activity
- they monitored 24 women and men and found a sleep wake cycle of 24 hours 11 minutes
argued psychological rhythms developed indirectly on basic circadian rhythms such as people tend to peak at different times
blake - particpants asked to carry out several tasks at five different time - 8 1030 3 330 9 found best performance at 9 and 2nd best performance at 10 30 in the morning.
however , other studies suggested performance peaks at noon
Menstrual cycle is one of the most common examples of an infradian rhythms.
the menstraul cycle is governed by two hormones known as oestrogen and progesterone, produced by the endocrine gland and released into the bloodstream. These hormones cause the lining of the womb to become engorged with blook and for one egg to be ripened and released . The lining of the womb is shed with blood if the egg is not fertilised . This process happenes every 28 days when an egg is released from the ovaries.
Martha Mcclintock was the first person to recognised menstrual synchronisation amongst females whilst at universtiy in 1971. She noted that 135 females menstrual cyces became synchronised in her dorm . She believed this was caused by pheromones being released by an individual into the air/environment having specific reactions on other individuals. She thought that their maybe a female heromone that affects the timing of other females cycles
infradian rhythms research
martha mcclintock and stern
10 year longitudinal study
29 females ages 20-35 experiencing irregular periods
samples of pheromones taken from 9 particpants by placing a cotton pad underneath their arms for atleast 8 hours
each pad was treated with alcohol and frozen then wiped under the noses of 20 other women on a daily basis.
Finding- that 68% responsded to the phermones having their periods either shorten from 1-14 days or lenghten from 1- 12 days depedning on when in the menstrual cycle they were taken
evaluation of infradian rhythms
russel et al - done a similar study and found similar results . 1 reason for this happening is argued by the evolutionary perspective by suggesting that females in social groups should have children at the same time so they can share child caring activitues such as breast feeding
strong evidence for phermonal changes in rats however generalisbility is lacking here as human behaviour is considered to be more complex especially when considering mating . For example a female boar when ovulating and when smeelling the saliva of a male boar spread her leg in the mating pose.
cause and effect is uncertain - unsure whether the pheromones acted throuhg the skin on the upper lip or through the mucus membranes in htier noses
sample bias - all females
arteficial so lack mundane realism
Infradian and SAD
sad is considered to be an infradian rhythm as it tends to happen in the winter months so hence more than a 24 hour cycle
sad is when an individual suffers from severe depression dring the winter months
symptoms include feelings of guilt low self esteem lethargy and insomnia
causes are uncertain because this is a relatively new pschypathology but it has been suggested that it is due to the lack of light during the night time . This causes the pineal gland to secret melotonin which makes an individual feel sleepy . In turn this affects the production of serotonin which is implicated in depression . as it is primarily produced during darkness more is produced during the long wintern nights
treatment barlow and durrand suggest that phototherapy is an effective therapy wherevy sufferers are exposed to 2-3 hours of intense light in the moring . the assumption is that this will reduce the production of melotonin
evalaution of sad
- application is efficient as it is easily used and lacks side affects
- replication such as eastman and winston have also suggested that photothrepay is a successsful form of treatment
- sme argue that some people may have a genetic predisposition to sad or stress features that can contribute to its offset
It has been found that there is an ultradian rhythm within the sleep cycle . New physioloigcal techniques have shown that there are repeated cycles whilst we sleep each lasting 90 minutes.
how are they measured ?
eeg - measures brain activity , electrodes are attached to an individuals scalp in which recordings can be made as electrical impluses that occur . These are recorded as a trace . this enbales us to see whether someone is asleep awake and identify which stage of sleep they are in
eog- measures eye activity . It has been shown that rem is connected to dreaming . The others stages of sleep are known as nrem or slow wave sleep sws.
emg- measures muscle activity in the chin to see whether it is tense or relaxed.
whilst in rem we undergo a brief period of vivid and eratic dreams when the brain is monitored by the eeg this stage is similar to when we are actually awkae, yet it is difficult to actually wake someone during rem sleep
nrem sleep consists of four stages :
stage one is the drifitng off period . here are breathing becomes slower are blood pressure falls and heartbeat is more irregular . At this stay the person can be easily woken
stage two when considering the eeg the brain waves are slower and larger with an occasional quick burst of activity which is known as k complexes the brain responding to external stimuli
stage three is the beginning of deep sleep the brain waves are long and slow
stage three is the deepest stage of sleep the brain waves are large and slow but jagged in pattern . At this time and indivdual is difficult to wake and if is will usually be groggy and disorientated . Sleep walking and talking is mostly likely to take place in this stage .
after we enter rem sleep wehere are muscles are seen to be inactive but our eyes are eratically moving heart rate and blood pressure fluctuate and our breathing rate is higher,
research into ultradian
dement and kleitman
recorded the eeg records of 9 adults who were awkaedned by a bell at each stage . here they were asked to report their feeling whether they were dreaming and the content of the dream . they found that in rems sleep dreams was rememebred 80-90% of the time compared to the 7% that reported fdraming in nrem sleep .
this supports the relationship between rem and dream activity
dement and wolport identified key factors connected with dream after replicating the above study .
all humans dream and if they claim they do not it if often because they have just forgotten thier dream
lenght of dream often corresponds with the incident being dreamt about
it is misguided to think that dreams only last for one to two seconds they can actually last up to 15 minutes
research into ultradian
eye movements observed in rem sleep can correspond to the dream content
content can also be affected by events experiences during the day or external stimulie.g they sprayed water onto the faces of some particpants whilst in rem sleep more than often the particpants reported aving a dream with a water theme compared to control
evaluation of ultradian research
it has been argued by other psychologists that there has been 70% dream recall in nrem sleep
the research is often arteficial as carried out in a sleep lab therefore particpants may respond differantly as sleepig in their own bed does not really compare
these are rhythms that are from within an organism .
in humans and mammals are internal body clock is a small cluster of ceel called the suprachiasmatic nuclei scn - which are located in the hypothamalus region of the brain
the scn is located above the optic chiasm and therefore can receive information directly from the retina therefore in humans the scn clock maintain a 24 hour clock rhythms from the input of the eye denoting whether it is day or night
scn generates its own rhythm from portein synthesis . it produces proteing every few hours and stops until level inhibits further production again for hours . when this level drops below a certain threshold the scn produces protein again .
the pineal gland is responsible for our biological clock . as recieves input directly from the scn the scn take input on day length from the retina and interpets it and oasses t on to the pineal gland
the pineal gland produces melotoning making a person feel sleepy
research into endogenous pacemakers
ralph et al bred a group of hamster with an abnormal 20 hour sleep wake cycle and transplanted their scn into foetuses with a normal 24 hour cycle . They found that the foetuses adopted a 20 hour sleep wake cycle . when they reversed this tranplanting the scn cells from the mutant breed to the normal breed they followed a 24 hour sleep wake cycle . the hamsters rhythms no longer matched thier own genes but the scn donar.
EVIDENCE FOR THE IMPORTANCE OF THE SCN MAINTAINING CIRCADIAN CLOCK
green and gillette
recorded electrodes in rats and whick picked up rhytmic bursts or activity from the scn that varied according to a 24 .5 hour cycle .
friedman et al
anatomical studies in humans show presense of a pathway beteen the retina to scn
although futton and bailey found brain tumours which had damaged scn region consequatnyl creating disroders in sleep wake cycle
rhythmas can be synchronisedby exogenous zeitgebers e.g light a shift in cues e.g travelling across time zones rhythms becomes enligned .t his allignment is called entrainment
light dominanat eveirnmental time cue for circadian rhtyhms
campbell and mruphy - importance of light zeitgebers not entering the eyes but behing tht knees . montiored body temperature of 15 volunteers who slept in a lab
awkone at cetain times and light pad was shone on the back of thier knees . this area was chosen because the blood vessels are closer to the surface of the skin and because it unables particpants to see the light
found changes in their circadian rhytms suggesting that chemical changes in the blood can ifnluence the scn
evaluation of exogenous zeitgebers
this research should be taken with caution as other studies have not found similar findings .
it should also be recognised that the particpants were exposed to a low level light
also arteficial lacks ecological validity