Biological Rhythms (Biopsychology)

Question 1

Circadian Rhythm

Answer 1

A biological rhythm that have a periodicity of 24 hours. Periodicity in relation to biological rhythms is the time between one peak or maximum value and the next peak or maximum value.

-Sleep-waking cycle: one period of sleep and one of waking every 24 hours

-Core body temperatures: one peak and trough every 24 hours

-Hormone production: melatonin levels peak in the dark and are at its lowest during the daylight

Question 2

Photosensitive retinal ganglion cells

Answer 2

contribute to the regulation of pupil size and other behavioural responses to ambient lighting conditions

light (exogenous zeitgeber) provides the primary input to the SCN system (endogenous pacemaker)

after light is detected by these light sensitive cells, they send messages about environmental light levels directly to the SCN

Question 3

Core body temperatures

Answer 3

• Our body temperature varies by about 2’C during the day
• lowest approx. 4 am
• peak approx. 6 pm
• the warmer we are, the better we perform

Folkard et al. (1977)
• tested reading comprehension in morning and afternoon
• children did better after 3pm than those who did at 9am

Gutpa (1991)
• IQ scores lower at 2pm than 7pm

Question 4

Siffre 1962

Answer 4

French speleologist who spent two months living in total isolation in a subterranean cave without access to a clock, a calendar or the sun.
Sleeping and eating only when his body told him to, his goal was to discover how the natural rhythms of human life would be affected by living “beyond time”.
His free running body clock did go back to the usual 24 hour cycle.
He had weighing scales and could work out his circadian rhythm based on what he weighed in the morning and evening

Question 5

Siffre’s study is supported by Aschoff et al. (1976)

Answer 5

Placed participants in a bunker for 4 weeks with no natural light

They settled into a sleep/wake cycle of between 24/25 hours (apart from one which extended to 29 hours)

Question 6

Melatonin and breast milk

Answer 6

• Melatonin is secreted in breast milk but it varies throughout the day to help a baby know when to sleep or wake
• Babies who are formula fed find it harder to regulate their sleep

Question 7

Folkard et al. (1985)

Answer 7

isolated 12 participants from natural light for 3 weeks (dark cave), manipulating the clocks so that only 22 hours passed a day
none of the participants could adjust comfortably to the pace of the clock (except one), showing the strength of the circadian rhythm as a free-running cycle and questions the extent to which it can be overridden by exogenous zeitgebers

Evaluation: it is difficult to generalise the findings from studies of the sleep/wake cycle because individual cycles can vary, in some cases from 13-65 hours. There are also age differences in the sleep/wake cycles

Question 8

Ultradian and Infradian rhythms

Answer 8

Ultradian: a type of biological rhythm with a frequency of more than one cycle in 24 hours
BRAC: Basic Rest and Activity Cycle, Sleep stages

Infradian: a type of biological rhythm with a frequency of less than one cycle in 24 hours: menstrual cycle, SADnd lack of melatonin during winter months

Question 9

Menstrual cycle

Answer 9

Follicle Stimulating Hormone (matures the egg, secreted from pituitary gland), Oestrogen (releases egg via oviduct, secreted from ovary), Luteinising Hormone (ovulation), Progesterone (builds up lining of uterine walls)

regularity of approximately 28 days

Ovulation occurs when luteinising hormone is at its peak

the cycle is regulated by the pituitary gland

Question 10

McClintock

Answer 10

Pheromones can change the menstrual cycle of a women not on hormonal contraception

McClintock tested this using strips which had been held under women’s armpits. These were then placed under other women’s noses

If women could sync their cycles this way, they would be able to look after babies and each other together, which would be evolutionarily advantageous

Question 11

Seasonal Affective Disorder

Answer 11

Annual rhythms are related to seasons, in particular migration in response to lower body temperatures
This is reflected in human behaviour as people, particularly women, can become severely depressed in the winter months

SAD: a depressive disorder which has a seasonal pattern of onset (DSM-5)
-The main symptoms are persistent low mood alongside a general lack of activity and interest in life

Circannual rhythm: melatonin is secreted for a longer period of tie due to a lack of light. This is thought to have an effect on the neurotransmitter serotonin, creating depressive symptoms
The winter is also associated with an increase in heart attacks and there is a robust annual rhythm in human deaths with most people dying in January

Question 12

Practical application of Circannual rhythm research

Answer 12

lack of sunlight increases depression in some people, phototherapy has been found to be an effective treatment

-Eastman randomly assigned 96 patients with winter SAD to one of three bright light treatments that are about 10-20 times brighter than ordinary indoor lights

-patients either got an hour and a half of bright light in the morning, and an hour and a half in the evening, or a morning placebo of two deactivated negative ion generators

-after three weeks, more people in the morning light group than the placebo group showed more complete or near-complete remission of their symptoms.

-the response to evening light was also better than placebo but not at a level of significance

-concluded that effective phototherapy fostered full remission of depression

However 30% of sufferers in the placebo group also seemed to recover

Question 13

Kleitman 1969

Answer 13

described sleep cycle though the states as the Basic Rest and Activity Cycle (BRAC). He also suggested that we move through a similar cycle of alertness and fatigue during the day. For example, research suggests that we can concentrate for approximately 90 minutes before we begin to lose concentration and begin to feel hungry and fatigued.
Our understanding of sleep comes from EEG recordings (Electroencephalogram)

Question 14

Sleep Cycle Stage 1

Answer 14

Non-REM sleep: transition from wakefulness to sleep. Last less than 10 minutes and is marked by slowing heartbeat, breathing and eye movements as well as relaxing of muscles.

Alpha brain waves

Question 15

Sleep Cycle Stage 2

Answer 15

Non-REM sleep: is the period of light sleep before you enter deeper sleep. Lasts roughly 20 minutes. Further slowing of heart rate, breathing and the brain begins to produce bursts of rapid, rhythmic brain wave activity known as sleep spindles.

Theta brain waves

Question 16

Stage 3

Answer 16

Final stage of non-REM sleep: deepest period of sleep and lasts 20-40 minutes. Your heart rate and breathing are at the lowest levels and your muscles are so relaxed that it may be hard to awaken you

Delta brain waves

Question 17

REM (Stage 4 of the sleep cycle)

Answer 17

Occurs 90 minutes after sleep onset and is much deeper sleep than any of the stages of non-REM. Defined as rapid eye movement and an almost complete paralysis of the body.

REM brain waves

Question 18

(Biological Rhythms Evaluation) Sleep Research

Answer 18

Dement and Kleitman (1957) measured brain activity using electroencephalogram controlling for the effects of caffeine and alcohol. REM sleep was highly correlated with dreaming the more vivid, the more active. Walking people up during the REM stage people could recall very clearly what they dreamed.
This finding has been replicated on multiple occasions.

Question 19

(Biological Rhythms Evaluation) Evolutionary basis of the menstrual cycle

Answer 19

McClintock’s study has evolutionary value- for our ancestors it may have been advantageous for females to menstruate together and therefore fall pregnant around the same time.
This would mean that new-borns could be cared for collectively within a social group increasing the chances of the offspring’s survival

However:
The validity of this perspective has been questioned by some. Schank (2004) has argued that there were too many females cycling together within a social group, it would produce competition for the highest quality males and therefore lowering the fitness of any potential offspring.
The avoidance of synchrony would appear to be the most adaptive evolutionary strategy

Question 20

(Biological Rhythms Evaluation) Evidence for sleep stages

Answer 20

Dement and Kleitman (1957)

Replications of this investigation have noted similar findings though the small size of the original sample has been criticised

Question 21

(Biological Rhythms Evaluation) Animal studies

Answer 21

The role of pheromones in animal sexual selection is well documented
Sea urchins release pheromones into the surrounding water so other urchins in the colony will eject their sex cell simultaneously

However, evidence for the effects of human behaviour remains speculative and inconclusive

Question 22

(Biological Rhythms Evaluation) Practical application for SAD

Answer 22

One of the most effective treatments for SAD is phototherapy
This is a light box that simulates very strong light in the morning and evening
It is thought to reset melatonin levels in people who have SAD (Eastman et al, 1998)
However, the placebo effect calls into question the effect of phototherapy

Question 23

(Biological Rhythms Evaluation) Methodological limitations in synchronisation studies

Answer 23

Stress, lifestyle, diet ad exercise can all change a woman’s cycle and these may act as confounding variables
This suggests that the results of McClintock’s study would be down to chance
These studies used small samples and did rely on participants self-reporting
The study by Trevathan et al. (1993) failed to find any evidence of menstrual synchrony
-In this study 29 cohabiting same sex couples kept a daily diary of their cycle, sexual activity and intimate contact

Question 24

The suprachiasmatic nucleus (SCN)

Answer 24

-a tiny bundle of nerve cells located in the anterior part of the hypothalamus in each hemisphere in the brain
-it is one of the primary endogenous pacemakers in mammalian species and is influential in regulating most circadian rhythms
-nerve fibres connected to the eye cross in an area called optic chiasm on their way to the visual area of the cerebral cortex
-it receives information about light directly form this- even when our eyes our closed

Question 25

Entrainment

Answer 25

• process of resetting the biological clock in line with external time cues
• synchronises the circadian rhythms

Question 26

The Pineal Gland and Melatonin

Answer 26

Pineal gland increases the production of melatonin at night as it induces sleep and is inhibited during periods of wakefulness

Question 27

Animal studies and the SCN

Answer 27

DeCoursey et al. (2000)destroyed the SCN connections in the brains of 39 chipmunks, who were then returned to their natural habitat and observed for 80 days
The sleep/wake cycle f the chipmunks disappeared and by the end of the study, a significant proportion of them had been killed by predators (due to them being awake and vulnerable, when they should have been asleep)

Ralph et al. (1990) bred ‘mutant’ hamsters with a 20hour sleep/wake cycle. When the SCN cells from the foetal tissue of mutant hamsters were transplanted into the brains of normal hamsters, the cycle of the second group defaulted to 20hours.

Question 28

Bugress et al. (2003)

Answer 28

found that exposure to bright light prior to an east-west flight, decreased the time needed to readjust to local time on arrival. Participants exposed to continuous bright light shifted their circadian rhythm by 2.1 hours whereas those exposed to intermittent bright light shifted their rhythm by 1.5 hours and those exposed to dim light shifted theirs by just 0.6 hours.
As a result, participants in the first condition felt sleepier two hours earlier in the evening and woke two hours earlier in the morning, i.e. closer to local time conditions

Question 29

Campbell and Murphy (1998)

Answer 29

Procedure: 15 participants were woken at various times and a light pad was shone on the back of their knees

Results: the participants deviated from their usual sleep/wake cycle by up to 3 hours

This suggests that light is a powerful exogenous zeitgeber that need not necessarily rely on the eyes to exert its influence on the brain. It may be detected by skin receptor sites on the body even when not received by the eyes.

Question 30

Social Cues

Answer 30

At 6 weeks of age, the circadian rhythm begins and by 16 weeks, most babies are entrained

The schedule imposed by parents is said to have a large influence here, including adult-determined mealtimes and bedtimes

Jet lag research found that adapting to local eating and sleeping times is an effective way for entraining circadian rhythms

Question 31

(Evaluation of EP and EZ) Not just one ‘master clock’

Answer 31

Research has revealed there are numerous circadian rhythms in many organs and cells of the body- peripheral oscillators found in the adrenal gland, oesophagus, lungs, liver, pancreas, spleen, thymus and skin

Although they are influenced by SCN, they can act independently

Damiola et al (2000) demonstrated how changing feeding patterns of mice could alter the circadian rhythms of cells in the liver by up to 12 hours, whilst leaving the rhythm of the SCN unaffected

Question 32

(Evaluation of EP and EZ) Evaluation of Exogenous Zeitgebers

Answer 32

Siffre cave study: shows circadian rhythms can be maintained without natural light

Campbell and Murphy (1998) shone light onto the back of the knees of 15 participants when they woke them at various points in the night (they woke them up with the light on the knee). They managed to vary their sleep cycle by up to three hours
Light is detected even by parts of the body aside from the eyes, their are
The interruption also would affect their sleep

Question 33

(Evaluation of EP and EZ) Ethics in animal studies

Answer 33

DeCoursey et al. - animals were exposed to considerable harm and risk when they were returned to their natural habitat

Question 34

(Evaluation of EP and EZ) Influence of EZ might be overstated

Answer 34

Miles et al. (1997) recounts the story of a young man, blind from birth with a circadian rhythm of 24.9 hours. Despite exposure to social cues, his sleep wake cycle could not be adjusted, and consequently, he had to take sedatives at night and stimulants in the morning to keep pace with the 24 hour world
being blind, his optic nerve was not exposed to light
shows the influence of EZs is limited

Question 35

(Evaluation of EP and EZ) Methodological issues

Answer 35

Campbell and Murphy’s study has yet to be replicated. However, researchers have been critical of the manner in which the study was conducted and have suggested that there may have been some light exposure to participants’ eyes- a confounding variable
Isolating one zeitgebers does not give insight into the many other zeitgebers that influence the sleep/wake cycle and the extent to which they interact