Biopsychology

Question 1

What is the function of the PNS? Give an example.

Answer 1

Sends information from the outside world to the CNS and transmits messages from the CNS to muscles and glands in the body.

Eg. Tells the muscles to pick up a spoon.

Question 2

What is the function of the somatic nervous system? Give an example.

Answer 2

To transmit information from receptor cells in the sense organs to the CNS. It also receives information from the CNS that directs muscles to act.

Eg. The act of picking up the spoon.

Question 3

What is the function of the autonomic nervous system? Give an example.

Answer 3

To transmit information to and from internal bodily organs. This operates automatically. There are two divisions: sympathetic and parasympathetic.

Question 4

What is the function of the CNS? Give an example.

Answer 4

It is the origin of all complex commands and decisions, consisting of the brain and spinal cord.
Eg. Deciding whether to pick up a spoon.

Question 5

What is the autonomic nervous system divided into?

Answer 5

SYMPATHETIC NERVOUS SYSTEM-increases bodily activities.

PARASYMPATHETIC NERVOUS SYSTEM-maintains or decreases bodily activities.

Question 6

What is the function of a neuron?

Answer 6

To receive and transmit information to other cells.

Question 7

What are the three types of neuron?

Answer 7

SENSORY-to tell the brain about the external and internal environment by processing information from the senses.
RELAY-carry messages from one part of the CNS to another and they connect relay and motor neurons.
MOTOR-carry signals from the CNS, which helps both organs, including glands and muscles, function.

Question 8

What can the PNS be split into?

Answer 8

SOMATIC NS - transmits information to and from senses, and to and from CNS.
AUTONOMIC NS - transmits information to and from internal organs to sustain life processes.

Question 9

What is synaptic transmission?

Answer 9

The process by which nerve impulses are carried across the small gap (synapse) between one neuron and another. The electrical nerve impulse travels down the neurone and prompts the release of neurotransmitters at the pre-synaptic terminal. These chemicals are released into the synaptic fluid and taken up by the adjacent neurone at the synaptic terminal and the chemical is converted again to an electrical impulse.

Question 10

What are the two types of messages (action potential) of the neurotransmitters?

Answer 10

EXCITATORY POTENTIAL - make it more likely for the neuron to fire.
INHIBITORY POTENTIAL - make the neuron less likely to fire.

Question 11

What is the endocrine system? Give an example.

Answer 11

A system which has a series of glands which release chemicals (hormones) throughout the body via the blood and other bodily fluids. This communicates messages to the organs of the body.
Eg. The adrenal gland releases adrenaline for the fight or flight response.

Question 12

What are the steps for the fight or flight response?

Answer 12

1. The HYPOTHALAMUS (deals with basic survival functions) recognises there is a threat
2. The adrenal medulla triggers the release of adrenaline.
3. Adrenaline prompts physical changes (eg.increased heart rate, breathing, muscle tension, pupil dilation, sweat production, reduced functioning of digestive and immune systems).

Question 13

What is the structure of a neuron?

Answer 13

The NUCLEUS contains genetic information of the cell. Branch-like structures, called DENDRITES, protrude from the cell body and carry nerve impulses from neighbouring neurons to the cell body. The AXON then sends this impulse away from the cell body down the length of the neuron. This is covered in the MYELIN SHEATH which protects the axon and speeds up electrical transmission of the impulse. This is segmented by gaps called NODES OF RANVIER which forces the impulse to ‘jump’ across the gaps. At the end of the axon is an AXON TERMINAL which communicate with the next neuron in the chain across the synapse.

Question 14

What is the central nervous system?

Answer 14

Comprises of the brain and the spinal cord.

Question 15

What is the peripheral nervous system?

Answer 15

Includes all of the nervous system throughout the rest of the body.

Question 16

What does the autonomic nervous system split into?

Answer 16

Sympathetic nervous system: generally increases bodily activities.
Parasympathetic nervous system: generally maintains or decreases bodily activities.

Question 17

Who found evidence for why you can’t perceive when you’re touched in two different places simultaneously?

Answer 17

Yamamoto and Kitazawa - if someone is touched simultaneously on the toe and shoulder you can’t tell which was touched first and it feels like they were touched at different times. It is argued that this is because of the difference between the distance from the brain.

Question 18

Research in the endocrine system

Answer 18

Feldman et al - The hormone oxytocin from the pituitary gland elicits a feeling of relaxation and calm and encourages strong bonding between mother and child.

Question 19

Evaluation of biological structures effecting behaviour.

Answer 19

It is hard to find a cause and effect relationship (eg we can find a correlation between oxytocin levels and increased relationship intensity, but not that oxytocin causes this. It could be argued that forming a relationship causes an increase in oxytocin levels).
It could be argued that using biological structures to underpin human behaviour can be seen as reductionist. This means that it is overly simplistic, because human behaviour and cognition is complex.
The reliability of this approach is high because evidence is totally objective.

Question 20

How does the short term stressor work in the fight or flight response?

Answer 20

The amygdala (in the brain) registers a threat and starts the sympathetic nervous system working. As a result, the adrenal glands release adrenaline. Once the short term stressor disappears, the parasympathetic nervous system will kick in and inhibit all of the bodily responses.

Question 21

How does the long term (chronic) stressor work in the fight or flight response?

Answer 21

If the stressor continues for a long period of time then the body must find new resources before it runs out of energy and dies. To do this, the hypothalamus kicks in and informs the pituitary gland that cart idol is needed. The pituitary gland will communicate with the adrenal cortex to release cortisol. This turns stored fat into energy for use in fighting off the stressor for longer. Cortisol also suppresses the immune system.

Question 22

What are the four ways of studying the brain?

Answer 22

Functional Magnetic Resonance Imaging - the use of a magnetic field to track the flow of oxygenated blood. An area with a lot of oxygenated blood shows an area is active. Maps can be produced to show active areas of the brain. The participant has to lie in a large magnetic field and lie still.
Electroencephalogram (EEG) - small electrodes are placed on the scalp which detect electrical impulses, triggered by nerve cell activity. The wave shapes produced from this shows the frequency as well as the strength of brain activity. EEG is used commonly for sleep research or measuring and diagnosing brain disorders (particularly epilepsy and Alzheimer’s).
Event-related potentials (ERPs) - these are types of brainwave that are triggered by particular events. Electrical activity can be pinpointed which shows neuronal activity is active in an area. ERPs aim to focus on particular activity by presenting participants stimulus over and over again, any activity which doesn’t occur consistently is discarded.
Post-mortem examinations - physical examination of the brain. This is usually used when patients exhibit extraordinary behaviour. Areas of the brain are examined to establish the likely cause of a deficit or disorder that the person suffered in life. The extent of the difference could then be assessed by use of comparing with a neurotypical brain. Researchers are able to get a clear idea of the cause of abnormality. Eg Broca carried out a post mortem of Tan who had speech problems. Broca was able to identify the ‘Broca’s area’ of the brain which produces speech.

Question 23

Which cortex is responsible for initiating conscious movement in the body?

Answer 23

The Primary Motor cortex - this is located towards the surface of the brain, in the frontal lobe. Each section is responsible for a different part of the body and are placed in logical locations. Each half of the brain controls the opposite side of the body. The cortex can change shape due to training or practice.

Question 24

Which cortex is responsible for receiving sensory information?

Answer 24

Somatosensory cortex - this is located close to the motor cortex in the parietal lobe. Each section is mapped to a specific area of the body.

Question 25

In which lobe is visual information encoded?

Answer 25

The occipital lobe - projections from the retina are received via the thalamus. Information is then passed to temporal and parietal lobes and processed consciously.

Question 26

Which area is responsible for hearing?

Answer 26

Auditory cortex - located within the temporal lobes. The stimulus converts to nerve impulses in the cochlea. It then reaches the brain stem where decoding takes place before reaching the thalamus, which processes the stimulus further. It then travels via the auditory nerve to the auditory cortex in the brain.

Question 27

Where is the Broca’s area found?

Answer 27

It is located in the left frontal area. The principal task for this area is the production of speech.

Question 28

Where is the Wernicke’s area found?

Answer 28

It is found in the left hemisphere and is responsible for understanding speech. A symptom for Wernicke’s aphasia is not understanding.

Question 29

Evaluation of localisation of function - support.

Answer 29

Aphasia - this is the inability to understand or produce speech. It has been found that those with expressive aphasia (who can’t produce speech) have damage to their Broca’s area. Those with receptive aphasia (who can’t understand speech) have damage to their Wernicke’s area.
Brain scanning techniques - consistently show that different regions are responsible for different tasks in the brain. Paulesu found different areas of the brain were used during the completion of different tasks.
Case studies - unique cases of neurological damage support localisation. For example, Phineas Gage received serious brain damage in an accident. He survived, but damage to his brain affected his personality - he went from someone who was calm an reserved to someone quick-tempered and rude. The change in Gage’s temperament following the accident suggests the frontal lobe may be responsible for regulating mood.

Question 30

Evaluation of localisation of function - against

Answer 30

Equipotentiality - when the brain is damaged (through illness or accident) and a function has been compromised or lost, the rest of the brain can reorganise itself to recover the function. Humans can recover from damage to certain areas of the brain, going against localisation. Other areas of the brain can take responsibility of these tasks so the same neurological action can be achieved, showing the brain acts as a unit.
Contradictory evidence: Lashley suggest higher cognitive functions are not localised but distributed in a more holistic way. Lashley removed between 10% and 50% of the cortex in rats learning in a maze. No one area was more important than any other in terms of the rats’ ability to learn the maze.

Question 31

What is hemispheric lateralisation?

Answer 31

Research to suggest that each hemisphere of the brain have its own specialism.

Question 32

Who investigated the strange symptoms of split brain patients?

Answer 32

Sperry and Gazzaniga (1967) - Investigated the effects of hemisphere de connection to show that each hemisphere has different functions. This was a natural experiment using opportunity sampling and with a research design of repeated measures. Information would be shown to the different visual fields and then asked about this information with either their right or left hand. If information was shown to the RVF, they could answer correctly verbally. If information was shown to the LVF, they could draw the answer (for example) but not say it, because their right hemisphere isn’t the site of language centres.

Question 33

Strengths of split-brain research.

Answer 33

Shows lateralised brain functions: the left hemisphere is analytical and verbal and the right is adept at spatial tasks and music. The right hemisphere can only produce basic words and phrases but contributes emotional content to language. The distinction may be too simplified and several tasks associated with one hemisphere can also be carried out by the other.
Methodology: Sperry’s carefully standardised procedure of presenting visual information to one hemispheric field was ingenious. Participants stared at a fixed point with one eye. An image was flashed for 0.1 seconds, so the patient didn’t have time to move their eyes to spread information to both hemispheres. This allowed Sherry to vary aspects of the simple procedure and ensure only one hemisphere received information at a time.

Question 34

Limitations of split-brain research.

Answer 34

Issues of generalisation in relation to Sperry’s work: Only 11 patients took part in all variations and all had a history of seizures. This may have caused unique changes in the brain that influenced these findings. This limits the extent to which the findings can be generalised to normal brains - reducing the validity of the conclusions.
Differences may be overstated: modern neuroscientists argue the distinctions between the hemispheres are not at all clear-cut. Many behaviours that are typically associated with one hemisphere can be performed by the other when situations require. The apparent flexibility of the two hemispheres suggests some of the conclusions drawn by Sperry may be too simplistic.

Question 35

What is brain plasticity?

Answer 35

You can train your brain to be good at certain tasks, which changes the shape of your brain. The more you practice, the stronger the connections in your brain.

Question 36

Who studied evidence for brain plasticity?

Answer 36

Kuhn - got participants to play super Mario for at least 30 minutes a day for two months. They found significant increases in grey matter in various areas, such as the cortex, hippocampus and cerebellum. These link with greater spatial navigation, strategic planning, working memory and motor performance. A problem with this study is the influence of extraneous variables (one participant may have the advantage of being in education).
Davidson - found Tibetan monks, who were experienced in meditation, had higher levels of gamma wave activity in the brain compared to non-meditative controls. This linked to more efficient information processing to the brain. After meditation, even the control group had increased gamma wave activity, but the measures of the monks suggest long term practice could have deeper effects. A problem with this study is that the control group weren’t Tibetan, meaning that cultural differences may play a part as an extraneous variable.

Question 37

How does the brain develop?

Answer 37

At the age of two, you have more neural connections in your brain than you have as an adult, because your brain needs to prepare for any outcome. As you grow, these connections will change and reflect the skills you develop, and the ones you don’t.

Question 38

Who investigated neural connections in rats?

Answer 38

Kemperman (1998) - compared neural connections between rats in complex environments with those in laboratory cages. They found a greater number of connections in the complex environment, especially in the hippocampus, which is involved in forming new memory and the ability to navigate between locations.

Question 39

Who found evidence for brain development linked to stimulation in taxi drivers?

Answer 39

Maguire (2000) - compared the brains of experienced London taxi drivers with a control group. They found that the longer they had been driving, the larger their posterior hippocampus. This is involved in navigation and spatial awareness. Their overall hippocampus was no larger than the controls, but this section was enlarged.

Question 40

How can the brain recover after trauma?

Answer 40

Neural unmasking - Wall (1977) found that the brain contains a lot of dormant synapses, which don’t receive an input but can still be called upon in need. In the case of cell death, it is possible that these dormant synapses can be used as back up and replace the lost cells.
Stem cells - these are unspecialised cells which have the potential to perform any function. They can be implanted into the brain to deal with trauma recovery. These can be implanted into the brain to directly replace dead or dying cells; transplanted cells can secrete growth factors that ‘rescue’ injured cells or transplanted cells form a neural network, which links on uninjured brain site, where new stem cells are made with the damaged region of the brain.

Question 41

Supporting evidence for plasticity and functional recovery of the brain.

Answer 41

Practical application: research has contributed to the field of neurorehabilitation. Techniques include movement therapy and electrical stimulation of the brain to counter deficits to cognitive functioning experienced following a stroke. This shows that although the brain may have the capacity to ‘fix itself’ to a point, this process requires further intervention if it is to be successful.
Support from animal studies: Hubel and Wiesel sewed one eye of a kitten shut and analysed the brain’s cortical responses. The area of the visual cortex associated with the shut eye was not idle but continued to process information from the open eye. This pioneering study demonstrates how loss of function leads to compensatory activity in the brain - evidence of neural plasticity.

Question 42

Evidence against brain plasticity and functional recovery.

Answer 42

Age differences: Functional plasticity reduces with age. The brain has a greater propensity for reorganisation in childhood as it constantly adapts to new experiences and learning. However Bezzola et al demonstrated how 40 years of golf training produced changes in the neural representation of movement in participants aged 40-60. This shows that neural plasticity does continue.
Potential negative consequences: the brain’s ability to rewrite itself has maladaptive behavioural consequences. For example, 60-80% of amputees develop phantom limb syndrome - continued experience of sensations in the missing limb, usually painful and thought to be due to reorganisation in the somatosensory cortex. This suggests that structural and physical processes involved in functional recovery may not always be beneficial.

Question 43

What are circadian rhythms?

Answer 43

These are bodily processes which work over a set period of time. There are many cycles (e.g. Eating or sleeping) which seem to be caused by both external cues (exogenous zeitgebers) and internal biological cues (endogenous pacemakers). Circadian rhythms are the rhythms which work on a daily cycle. The most obvious of these is the sleep wake cycle.

Question 44

Who studied whether internal or external cues caused the sleep wake cycle?

Answer 44

Michael Siffre:
He conducted a temporal isolation study by living underground for a long period of time to study circadian rhythms without external cues. He tried to control conditions so only his body clock was influencing his behaviour. He did this by having no daylight, no clocks and no radios. He found that his body clock ticked more slowly, sometimes stretching it to 25 hours. He repeated this study when he was older and found that his circadian rhythm was longer (when he was 60 it stretched to 48 hours). His body generally kept to the sleep wake cycle, but it could vary unpredictably.
Folkard et al: studied a group of 12 participants living in a cave who were told to sleep at 11:45 and wake at 7:45. They gradually changed their cycle to 22 hours by which only one person conformed comfortably. This shows that strong endogenous pacemakers can’t be overridden by external environment.

Question 45

Evaluation of the Siffre study

Answer 45

Strengths:
Scientific methods - he measured various data scientifically (e.g. Pulse etc).
Weaknesses:
Poor population validity - data was collected by one man, so it is limited in generalising to the population at large. It was androcentric.

Question 46

Other circadian rhythms

Answer 46

Midnight - cortisol at its lowest.

4: 30 - body temperature at its lowest (36C) to heighten alertness.
6: 00 - cortisol (hormone) causes alertness and wakes you up.
14: 00-16:00 - a drop in body temperature causing a drop in energy.
18: 00 - body temperature at its highest (38C) to prepare to sleep.
21: 00 - Melatonin (hormone) increases during the day (inhibited by light) which makes you sleepy.

Question 47

What are ultradian rhythms?

Answer 47

Cycles that last for less than a day. For example, the need to eat food occurs more than once per day and this is due to a complex biological process involving some of the same areas of the brain as all other ultradian rhythms.

Question 48

What is an important ultradian rhythm?

Answer 48

The sleep wake cycle is an important circadian rhythm, but sleep is made up of stages itself.
Stage 1: 4-5% light sleep. Muscle activity slows down with occasional muscle twitching.
Stage 2: 45-55% breathing pattern and heart rate slows. Slight decrease in body temperature.
Stage 3: 4-6% deep sleep begins. Brain begins to generate slow delta waves.
Stage 4: 12-15% very deep sleep. Rhythmic breathing. Limited muscle activity. Brain produces delta waves.
Stage 3
Stage 2
R.E.M. sleep: 20-25%. Brainwaves start to speed up and dreaming occurs. Muscles relax and heart rate increases. Breathing is rapid and shallow.
Doesn’t go back to stage 1.

Question 49

What are infradian rhythms?

Answer 49

Rhythms that last for longer than a day. For example, the menstrual cycle. Stern and McClintock studied 29 women with irregular periods. Pheromones were taken from women at different stages of their cycle by swabbing the woman’s armpit which was later cleaned with alcohol. This was then put on other women’s upper lip. 68% of women experienced a change in their cycle to be closer to that of the ‘odour donor’.

Question 50

What are the biological processes involved in controlling the menstrual cycle?

Answer 50

It is under internal control of hormones (initially released by the pituitary gland) particularly oestrogen and progesterone, secreted by the ovaries. These cause physiological changes such as the release of an egg (ovum) from the ovaries and the thickening of the lining of the womb (uterus) in preparation for the arrival of the egg. If the egg is not fertilised, the lining of the uterus is shed and menstruation occurs. The contraceptive pill mimics the effects of pregnancy and cons the body into ceasing production of further eggs.

Question 51

Another example of an infradian rhythm.

Answer 51

Seasonal Affective Disorder (SAD): this is a mood disorder linked to the seasons. This involves a feeling of depression during the winter months where there is a significant reduction in exposure to natural light. The feeling of depression are thought to be caused by a surge in melatonin, a hormone inhibited by light but produced in abundance in the dark. It leads to sleepiness during the day and feelings of weariness. The treatment involves exposure to very bright light for 10 minutes a day.

Question 52

What are endogenous pacemakers and exogenous zeitgebers?

Answer 52

Rhythms are controlled and regulated by various cues. These cues can either be biological and internal (endogenous) or external (exogenous).

Question 53

What are endogenous pacemakers?

Answer 53

We have a biological clock in our brains known as the suprachiasmatic nucleus (SCN). This can be reset by external factors such as light etc, but left to itself, it can keep to a fairly regular rhythm. This is due to a complex lifecycle system of proteins, found within the SCN.

Question 54

What is the suprachiasmatic nucleus?

Answer 54

It responds to light levels (even when our eyes are closed) which happens because light comes through the optic nerve, picked up by the SCN. The SCN then communicates with the pineal gland, responsible for increasing or decreasing some of the hormone production in the body. In response to light, the pineal gland inhibits the production of melatonin. Melatonin makes you sleepy, so inhibiting it will allow you to be more awake.

Question 55

How can exogenous zeitgebers cause wakefulness?

Answer 55

Light hits the receptors in our eyes, which sends melanopsin (a protein) to the SCN. The SCN communicates with the pineal gland which inhibits the amount of melatonin. This causes wakefulness.

Question 56

Another example of an exogenous zeitgeber.

Answer 56

Social cues:
Research has suggested that one of the reasons we keep to our circadian rhythms is simply because those around us are keeping to theirs. For example, if you live with friends, you are more likely to eat or go to sleep the same time as them.

Question 57

Evidence for endogenous pacemakers.

Answer 57

Morgans hamsters: bred hamsters to have a circadian rhythm of 20 hours. SCN neurones from the abnormal hamsters were implanted into the controls, who then showed an abnormal rhythm. Confirmation of the effect of implanted SCNs is confirmed by the implanting of normal SCNs in abnormal hamsters. This shows the importance of endogenous pacemakers.
DeCoursey’s chipmunks: removed the SCN of chipmunks and normal controls. Those without SCN were more likely to get eaten by weasels because they weren’t sleeping. This suggests that internal cues are important because they didn’t sleep even with external cues.

Question 58

Evidence for exogenous zeitgebers.

Answer 58

Burgess et al: exposure to bright light prior to an east-west flight decreased the effect of jet lag. Volunteers were a part of three conditions (continuous bright light, intermittent light and dim light). Each of which shifted their sleep cycle back an hour a day over three days.
Skene and Ardent: the vast majority of blind subjects who still have light perception have entrained circadian rhythms. This suggests that the pathway between retinal cells and SCN is intact. This shows that light is an important cue.

Question 59

Evaluation of fMRI.

Answer 59

Strength: it is non-invasive. fMRI does not rely on the use of radiation and is safe. It produces images with high spatial resolution, showing detail by the millimetre. This means fMRI can provide a clear picture of how brain activity is localised.
Limitation: fMRI is expensive compared to other techniques and can only capture a clear image if the person stays still. It has poor temporal resolution because of 5-second lag between initial neural activity and image. This means fMRI may not truly represses the moment-to-moment brain activity.

Question 60

Evaluation of EEG.

Answer 60

Strength: it is invaluable in diagnosing conditions such as epilepsy. EEG has contributed to our understanding of the stages of sleep. EEG has extremely high temporal resolution. EEG can detect brain activity at the resolution of a single millisecond.
Limitation: information is received from many thousands of neurons. EEG produces a generalised signal from thousands of neurons so I t is difficult to know the exact source of neural activity. EEG cannot distinguish the activity of different but adjacent neurons.

Question 61

Evaluation of ERPs.

Answer 61

Strength: it is a very specific measurement of neural processes. ERPs are more specific than can be achieved using raw EEG data. ERPs also have excellent temporal resolution.
Limitation: lack of standardisation in methodology between studies. This makes it difficult to confirm findings in studies involving ERPs. Background noise and extraneous material must be completely eliminated. This may not always be easy to achieve.

Question 62

Evaluation of post-mortems.

Answer 62

Strength: they provided the foundation for understanding the brain. Broca and Wernicke both relied on post-mortem studies. They improve medical knowledge and help generate hypotheses for further study.
Limitation: causation may be an issue. Observed damage in the brain may not be linked to the deficits under review but to some other related trauma or decay. Post-morgen studies raise ethical issues of consent from the patient before death. Patients may not be able to provide informed consent (e.g. Patient HM).

Question 63

Strengths of circadian rhythm research.

Answer 63

Practical application to shift work: Boivin et al found that shift workers experience a lapse in concentration around 6am so mistakes and accidents are more likely. It has been found that shift workers are three times more likely to develop heart disease. Therefore research into the sleep/wake cycle may have economic implications in terms of how best to manage worker productivity.
Practical applications to drug treatments: research shows there are times during the day or night when drugs are more effective. Guidelines have been developed for the timing of dosing for a range of drugs including treatments for cancer and epilepsy. Thus research may have real life medical benefits.

Question 64

Limitations of circadian rhythm research.

Answer 64

Use of case studies and small samples: participants may not be representative of the wider population and this limits making meaningful generalisations. Siffre observed that his internal clock ticked much more slowly at 60 than when he was younger. This suggests that, even when the same person is involved, there are factors that may prevent general conclusions being drawn.
Poor control in research: participants deprived of natural light still had access to artificial light which was assumed to have no effect on free-running rhythms. But Czeisler et al adjusted participants’ circadian rhythms from 22 to 28 hours using dim lighting. This suggests that researchers may have ignored an important confounding variable in circadian rhythm research.

Question 65

Strengths of infradian and ultradian rhythms.

Answer 65

Evolutionary value on menstrual cycle research: it may have been advantageous for our ancestor females to menstruate together and become pregnant around the same time, so offspring could be cared for collectively, increasing their chances of survival. However the validity of this perspective has been questioned - this would produce competition for the highest quality males. From this point of view the avoidance of synchrony would appear to be the most adaptive strategy and therefore the one that would be naturally selected.
Research into SAD has practical applications: an effective treatment for SAD is phototherapy, a light box that simulates strong light in the morning and evening (thought to reset melatonin levels). This relieves symptoms in up to 60% of sufferers. But the same study recorded a placebo effect of 30% using a ‘sham negative-ion generator’. This casts doubt on the real value of phototherapy, which may not be effective because of expectations.

Question 66

Limitations of infradian and ultradian rhythms.

Answer 66

Methodology used in synchronisation studies: there are many factors that may change a woman’s menstrual cycle and act as a confounding variable (e.g. Stress, changes in diet). So any pattern of synchronisation is what we would expect to occur due to chance. Also, research involves small samples of women and relies on them self-reporting onset of their own cycle (may be inaccurate). This suggests that important aspects of synchronisation studies may lack validity.
Use of animal studies: the role of pheromones in animal sexual behaviour is well-documented and is the basis for most of our knowledge. For example, sea urchins release pheromones into the surrounding water so other sea urchins can eject their sex cells simultaneously. Evidence for the effects of pheromones on human behaviour remains speculative and inconclusive.

Question 67

Limitations of endogenous pacemakers and exogenous zeitgebers.

Answer 67

Animal studies: there is an issue generalising findings from research into the sleep/wake cycle from animal studies because cognitive factors may be more significant in humans. A more disturbing issue is the ethics of such research - animals were exposed to great harm and potential risk when returned to their natural habitat. Whether we learn from investigators on biological rhythms justifies the aversive procedures involved is a matter of debate.
The influence of exogenous zeitgebers may be overstated: Miles et al note the case of a man blind from birth with a circadian rhythm of 24.9 hours. His sleep/wake cycle could not adjust to social cues so he told sedatives at night and stimulants in the morning to align with the 24 hour world. Therefore there are occasions when exogenous zeitgebers may have little bearing on our internal rhythms.
The SCN may obscure other body clocks: body clocks are found in many organs and cells (e.g. Lungs, liver, skin, pancreas). They are highly influenced by the actions of the SCN but can act independently. This suggests there may be many other complex influences on the sleep wake cycle aside from the master clock.
Endogenous pacemakers and exogenous zeitgebers interact. Only exceptional circumstances do endogenous pacemakers free-run without influence of exogenous zeitgebers. Total isolation experiences (e.g. Siffre’ study) are rare and present an unrealistic way in which the system works. It makes no sense therefore to separate them for research processes.