Biopsychology Flashcards
What type of theory came before Localisation of Function?
A Holistic Theory
What does the holistic theory (of the brain) say?
The whole brain works together and all parts are involved in the processing of thoughts and action
What happened to switch from the holistic theory to the localisation theory?
Phineas Gage - a railway worker - was injured by a metal pole in his left frontal lobe and survived
He had personality changes but was still alive, suggesting the brain doesn’t operate as a whole or he would have died
There was a Paradigm Shift which introduced the localisation of function theory
What is Localisation of Function?
The idea that particular areas of the brain perform different tasks and are associated with different functions and parts of the body
How can we test if Localisation of Function is correct?
All damage to specific areas of the brain should result in the same problems to specific functions
What is Hemispheric Lateralisation?
The idea that the brain is divided into 2 hemispheres, and each side controls or dominates physical and psychological functions
Which side of the body does the right hemisphere control?
The left side of the body
Which side of the body does the left hemisphere control?
The right side of the body
What is the main part of the brain called?
The Cerebrum
How many hemispheres is the Cerebrum split into?
2
What is the outer layer of both hemispheres called?
The Cerebral Cortex
What are the parts of the brain (going round clockwise)?
Broca’s Area
Motor Cortex
Somatosensory Centre
Visual Cortex
Wernicke’s Area
Auditory Centre
What are the 4 physical areas of the brain (going round clockwise)?
Frontal lobe
Parietal lobe
Occipital lobe
Temporal lobe
What is in the Frontal Lobe?
Broca’s area
Motor cortex
What is in the Parietal Lobe?
Somatosensory centre
What is in the Occipital Lobe?
Visual cortex
What is in the Temporal Lobe?
Wernicke’s area
Auditory centre
What does the Motor Cortex do?
Generates voluntary bodily movement
Each hemisphere is responsible for the movement of the opposite side of the body
What happens when the Motor Cortex is damaged?
There is a loss of control of fine movements on the opposite side of the body to the damage
What does the Visual Cortex do?
Processes images and visual information
How does information get processed by the Visual Cortex?
The optic nerve is at the back of the brain and it travels from the eyes at the front to the back, crossing over, so each side of the visual cortex is responsible for the other eye’s visual field.
What happens when the Visual Cortex is damaged?
There is a loss of vision or difficulty processing visual information
What does the Auditory Centre do?
Recognises sounds and analyses speech-based information
What happens when the Auditory Centre is damaged?
There is difficulty processing auditory information
What does the Somatosensory Area do?
Sensory information from the skin is represented
It receives information such as touch, pressure, pain and heat/temperature
What happens when the Somatosensory Area is damaged?
Senses are not processed normally
What are the 2 language centres of the brain?
Broca’s area and Wernicke’s area
What side of the brain are the language centres?
Left
What language centre is Broca’s area?
Language Production Centre
What did Broca do/find?
He was a surgeon who studied patients who could understand language but not produce it (could not speak or write)
In their Post-Mortems, he found they all had damage to the same area in the left frontal lobe - Broca’s area
What happens when Broca’s area is damaged?
Broca’s Aphasia
What is Broca’s Aphasia?
Damage to Broca’s area means speech production is slower, more difficult, and takes more effort
What language centre is Wernicke’s area?
Language Understanding Centre
What did Wernicke do/find?
He studied patients who could speak but not understand or attach meaning to language
Their speech was fluent but did not make sense
He found they all had damage to the posterior portion of their left temporal lobe - Wernicke’s area
What happens when Wernicke’s area is damaged?
Wernicke’s Aphasia
What is Wernicke’s Aphasia?
Damage to Wernicke’s area means people can speak and produce language easily but it is meaningless as they cannot associate language with meaning
Evaluate Localisation of Function
Good - Brain Scan Evidence supports localisation of everyday brain functions
- Brain scans show Wernicke’s area is active in listening tasks and Broca’s area is active in reading tasks
In Addition…
- Long Term Memory studies show semantic and episodic memories are in different areas of the prefrontal cortex
- These give scientific, controlled evidence for localisation of the brain
HOWEVER
Bad - Artificial tasks were used for all of these scan studies
- This could mean they lack mundane realism and should not be used to formulate general laws of function of the brain
- Brains might be different in real life situations
Bad - Language may not be localised just to Broca and Wernicke’s areas
- 2% of modern researchers believe language in the brain is completely controlled by Broca and Wernicke’s areas
- Advances in brain imaging techniques shows language function is distributed more holistically than previously thought
- Language Streams have been identified and some include regions of the right hemisphere
- This suggests language may be more holistic than other functions
Good - Case Study support
- Phineas Gage
HOWEVER
Bad - Idiographic - brain damage is unique
What is Hemispheric Lateralisation?
The idea that the two sides of the brain aren’t alike, and brain functions are specialised to the different sides (lateralisation)
What is the left side of the brain said to be responsible for?
Language production and understanding language
Analytical Tasks
Auditory/linguistic tasks
What is the right side of the brain said to be responsible for?
Visuo-spatial tasks
Emotions
Recognition
Creative tasks
What joins the 2 hemispheres of the brain together?
A bundle of nerve fibres called the Corpus Callosum
What is the Corpus Callosum?
A bundle of nerve fibres connecting the 2 hemispheres of the brain
Which side of the body controls which?
Right controls left
Left controls right
The motor areas is cross-wired, meaning opposite control
What is the key research in hemispheric lateralisation?
Sperry’s Split Brain study
Who researched Split Brain patients?
Sperry
What makes Split Brain patients different?
They either have no corpus callosum, or it is damaged, meaning their hemispheres cannot communicate with each other
Why do people with Split Brains exist?
In the 1940s, lobotomies were performed on patients with epilepsy that cut their corpus callosums as they believed this was causing their epilepsy.
This left the patients unable to communicate across hemispheres.
(It could also be a birth defect where people are born without them, or some type of brain damage from an accident leaving them with a damaged one)
What was the procedure for Sperry’s split brain research?
- Used 11 split brain patients
- Used a controlled, special setting with screens that participants could only see half of
- The participants were shown an image or word on one side of the screen, meaning the information could only be perceived by one hemisphere
What were the findings of Sperry’s split brain research?
Saying what they saw:
- ppts could only say what they saw when they saw it in their Right Visual Field (right side of the screen)
- This is because the RVF sends information to their Left hemisphere, which is responsible for speech and language production
Drawing what they saw:
- ppts could only draw what they saw when they saw it in their Left Visual Field (left side of the screen)
- This is because the LVF sends information to their Right hemisphere which is responsible for creativity
- Not only this, but the ppts could only draw it with their Left Hand, due to the Right Hemisphere being in control of their motor production of the Left Side of the body
Describing what they touched:
- ppts could not describe an item they felt with their left hand, as the Right Hemisphere is linked to the left side, and this does not control descriptions, the Left Hemisphere does
Evaluate hemispheric lateralisation and Sperry’s split brain research
Hints:
Trees
Epilepsy
Odd one out
Good - Research support for hemispheric lateralisation
Fink
- Used brain scans to identify active areas when doing a visual task
- When they asked ppts to describe a global image such as a whole forest, the Right Hemisphere was more active
- When asked to process smaller aspects of an image such as an individual tree, the Left Hemisphere was more active
- This suggests HL is also a feature within a connected brain
HOWEVER
Bad - lacks mundane realism as it is an artificial task
Bad - Sperry could lack generalisability
- He did not use a control group with epilepsy
- This could mean differences in processing were from epilepsy, not lack of corpus callosum
- This matters because it may mean his findings lack generalisability to people who do not have epilepsy
Good - Research support from more split brain research
- Further research showed that split brain patients are faster to identify the odd one out, supporting the idea that they have different mental processing
- This matters because it supports Sperry’s ideas of Hemispheric Lateralisation
What is Plasticity/neuroplasticity?
The brain’s ability to change and adapt in its function and physical structure in response to its environment
What can the changes be in plasticity?
Fast or Slow
Positive or Negative
What age does the brain’s synaptic connections peak at?
3 years old
How many synaptic connections does a 3 year old have?
Around 15,000
What is Cognitive Pruning?
Deleting rarely used synaptic connections
How can Cognitive Pruning be used in plasticity?
New neural connections can be formed in response to new demands, and old unused ones can be deleted
Who is the key researcher for plasticity?
Maguire et al (she/her)
What was Maguire’s sample?
The brains of 16 male London Taxi Drivers who had been driving for at least 18months
What was Maguire et al’s procedure?
They observed 16 male London Taxi Drivers’ brains using MRI scans
They compared this to a control group of 50 people
What did Maguire et al find?
There was significantly greater volumes of grey matter in the posterior hippocampus in the taxi drivers compared to the control group
There was a positive correlation between the more experience the drivers had and the volume of grey matter
What is the Posterior Hippocampus associated with?
The development of spatial and navigational skills
What is grey matter?
Areas of the brain that are very dense with active neurons
What is white matter?
Areas of the brain that are less dense with active neurons but connect the areas of grey matter
Why did Maguire use London Taxi Drivers for her research?
They had to pass a test called ‘the Knowledge’ that consisted of highly complex questions about routes in London.
Drivers had to learn the names and directions of every street and junction in London, as well as important landmarks and stations.
What conclusions can be made from Maguire’s findings?
The learning for ‘the Knowledge’ altered the cab drivers’ brain structure
Plasticity exists
Evaluate Plasticity
Bad - plasticity may have negative behavioural consequences
- Brains’ adaptation to prolonged drug use has been found to lead to poorer cognitive functioning in later life
- In addition to this, 60-80% of amputees experience ‘Phantom Limb Syndrome’, where they still experience sensations in their missing limbs due to cortical reorganisation in the somatosensory cortex after limb loss
- This suggests not all brain adaptations are beneficial
Good - Plasticity may be a life-long ability
- Although it was previously suggested that plasticity slows down after the age of 21, research has shown that 40 hours of golf training produced changes in the neural representations of movement in 40-60 year old participants
- fMRI scans showed increased motor cortex activity compared to a control group
- This suggests plasticity is life-long
Good - Nurse student support
- med school patients had a brain scan before and after revising for their final exams
- there were increases in grey matter after revising, suggesting plasticity exists and adapted to fit more information
What is Functional Recovery?
Following injury or trauma, unaffected areas of the brain can adapt to compensate for the damaged areas.
Healthy areas of the brain may take over the functions of damaged, destroyed or missing parts of the brain
What is Functional Recovery an example of?
Plasticity
What is Spontaneous Recovery?
When functional recovery happens quickly after trauma.
It may slow down after this.
How does Functional Recovery work?
The brain can re-wire itself by forming new synaptic connections close to the area of damage
What are 3 types of Functional Recovery?
Unmasking
Axonal Sprouting
Neural Reorganisation
What is Neural Unmasking?
Secondary neural pathways may be activated to allow functioning to continue
What is Axonal Sprouting?
New nerve endings grow and connect with undamaged nerve cells to form new neural pathways
What is Neural Reorganisation?
Similar areas in the opposite hemisphere are recruited to do the tasks of the damaged area
Who is the key researcher for Functional Recovery?
Tajiri et al
What did Tajiri et al do?
Investigated the role of stem cells in producing functional recovery
What was Tajiri’s procedure?
They assigned rats with traumatic brain injury to 2 groups:
1) control group - received a solution with no stem cells near the area of damage
2) experimental group - received a transplant of stem cells near the area of damage
What were Tajiri’s findings?
3 months after the injury…
Rats with stem cell transplant showed development of neuron-like cells in the area of injury
The control group did not show this development
What can Tajiri conclude?
Stem cells can produce new cells in damaged areas of the brain, supporting functional recovery
Evaluate Functional Recovery
Good - Real World Application
- understanding plasticity has contributed to the field of neurorehabilitation
- This understanding encourages new therapies to be tried
- This can also help medical professionals know when interventions need to be made
Good - Research support from stroke patients
- Stem cells were given to 5 stroke patients who experienced a rare type of stroke
- All the participants recovered, compared to the 4% recovery rate that was typical of these stroke patients
- This suggests understanding functional recovery has already had a positive impact on real world medical procedures
Bad - Small Sample Sizes
- Most research into functional recovery has a small sample size due to them being quasi experiments (patients who have brain damage or have had strokes beforehand)
- This matters because most of the time there is no control group, and so it is hard to generalise and use findings scientifically
How many ways are there to study the brain?
4
Why do we study the brain?
For localisation - to see which parts of the brain carry out what function
What are the 4 ways of studying the brain?
Functional Magnetic Resonance Imaging (fMRI)
Electroencephalogram (EEG)
Event Related Potential (ERP)
Post-Mortem
What does fMRI stand for?
Functional Magnetic Resonance Imaging
What does EEG stand for?
Electroencephalogram
What does ERP stand for?
Event Related Potential
How do fMRI scans work?
- They detect changes in blood oxygenation that occurs in specific areas of the brain as a result of activity (active areas need more oxygen so more blood goes there)
- Activation maps are produced. These are 3D images that show which areas are using the most oxygen, so we know which areas are the most active.
Evaluate fMRI scans
Good - non-invasive
- doesn’t rely on radiation
- risk free
- easy to use
Good - high spatial resolution
- the details are depicted by the mm so we can see a clear location
Bad - low temporal resolution
- there is a 5 second delay from brain to screen, so the results may not be accurate
Bad - expensive
Bad - inconvenient
- no metal is allowed –> bad for people with replacements/pacemakers
- requires you to lie still –> bad for people with claustrophobia
How do EEGs work?
- They measure the electrical activity in the brain via electrodes that are fixed on to an individual’s head using a skull cap
- It creates a screen recording that represents brainwave patterns from millions of neurons, which provides an overall account of brain activity
Evaluate EEGs
Good - Used as a diagnostic tool
- can spot arrhythmic patterns of activity, so are good for diagnosing things like epilepsy
Good - High temporal resolution
- can detect brain activity at a resolution of 1 millisecond
Bad - Invasive
- electrodes on head can mean there are demand characteristics in studies
- uses radiation which could be harmful
Bad - Generalised results
- the data is produced from millions of neurons, so we may be unsure of which neuron is responsible for which action, and where the neurons are
How do ERPs work?
- Uses statistical analysing to isolate EEG data:
- Removes extraneous brain activity to see specific responses to certain stimuli and tasks
(e.g. can remove motor and cognitive events to see only sensory events) - The brain waves triggered by particular events (ERPs) are all that is left
Evaluate ERPs
Good - Specific
- They can clearly identify the neural processes and the areas they take place in
Good - High temporal resolution
- Uses EEG data which can be detected in 1 millisecond
Bad - Invasive
- Uses data from EEGs which uses radiation and skullcaps
Bad - Difficult
- It may take time or be difficult to completely remove extraneous neurons
Bad - Lack of standardisation
- There is no standard way of removing extraneous neurons and it might be difficult to confirm the findings
How does a Post-Mortem work?
- It analyses a person’s brain after their death
- It usually studies people with abnormalities or rarities
- It allows us to see the areas and extent of damage of the brain and establish the likely cause of affliction
- Can compare to neurotypical brain structures
Evaluate Post-Mortems
Bad - Ethical Issues
- it is difficult to get consent
Bad - Time delay
- there could be years of waiting before a patient dies
Bad - Not useful for the patient
- the findings cannot be used to provide a treatment or help the patient
Bad - Causation is an issue
- the observed areas of damage might not be linked to the problems
Good - Provide a foundation of key processes in the brain
- Broca and Wernicke relied on Post-Mortems
Good - Can look at specific areas
- can clearly see the extent and location of the damage
What are Biological Rhythms?
Rhythms all living organisms are subject to that influence how our body systems behave
What are Biological Rhythms governed by?
Endogenous Pacemakers
Exogenous Zeitgebers
What are Endogenous Pacemakers?
Our internal body clock that regulates our biological rhythms
What are Exogenous Zeitgebers?
External Factors that affect and entrain our rhythms
What are the 3 main Biological Rhythms?
Circadian Rhythms
Infradian Rhythms
Ultradian Rhythms
Who are the 3 main researchers for Biological Rhythms?
Siffre (circadian)
McClintock and Stern (infradian)
Dement and Kleitman (ultradian)
How long do Circadian Rhythms last?
Around 24 hours
What is the main example of a Circadian Rhythm?
The Sleep/Wake Cycle
How does the Sleep/Wake Cycle work?
Exogenous Zeitgeber: Light
- Light helps us feel alert at day and drowsy at night due to the secretion and inhibition of Melatonin
Endogenous Pacemaker: Suprachiasmatic Nucleus (SCN)
- SCN lies above the optic nerve and provides information from the eye about light, even when the eyes are closed
Who researched Circadian Rhythms?
Siffre - Cave Study
What was Siffre’s aim?
To investigate the effects of the removal of Exogenous Zeitgebers to his sleep/wake cycle
What was Siffre’s Procedure?
- He took food, water and supplies with him to an underground cave for 2 months
- He recorded his activity and timed his sleep/wake cycle
What were Siffre’s Findings?
- His ‘free running’ biological clock settled to around 25 hours
- He continued a regular cycle afterwards
Which researchers replicated Siffre’s study in a WWII bunker?
Aschoff and Wever
What was Aschoff and Wever’s procedure?
A group of people spent 4 weeks in a WWII bunker deprived of natural light
What were Aschoff and Wever’s findings?
- All but 1 of the participants displayed a free-running cycle of 24-25 hours
- This suggests the natural sleep/wake cycle is just over 24 hours but is entrained by exogenous zeitgebers
Evaluate Siffre’s Cave Study
Good - Research Support from Aschoff and Wever
- All participants but 1 had a free running cycle of 24/25 hours
- This suggests the natural sleep/wake cycle is just over 24 hours but is entrained by EZs
Bad - Methodological Issues
- Siffre may not have fully isolated himself from EZs
- He used a head torch to find his way around the cave when he was awake
- This light would have still entered his SCN and could have replicated daylight for the time he was awake
- This matters because it could mean he did not measure what he set out to measure as he did not fully isolate himself from all EZs
Bad - Small Samples
- All research had small sample sizes
- We cannot be sure the cycles are only due to the removal of EZs as it may have just been participant similarities
- Siffre found his cycle had slowed down when he repeated it when he was older
- This could suggest we can only discuss the averages and should not generalise to all ages and cultures
Evaluate Circadian Rhythms
Good - It provides an understanding of the consequences that occur when the sleep/wake cycle is disrupted
- Desynchronisation can happen when shift workers have varying sleep/wake cycles as they become out of sync with their usual 24 hour cycles
- Research into this suggests a correlation between shift workers and: poor health, divorce, accidents at work and heart disease
- The understanding of Circadian Rhythms can help create safer work environments, and can allow for timetabling that keeps this in mind
Good - It can be used to improve medical treatments
- Rhythms help us understand the body’s processes such as heart rate, digestion and hormones
- Understanding this has led to Chronotherapeutics which is medical treatment suited to patients’ biological rhythms
- e.g. Taking aspirin before bed reduces blood platelet activity and can reduce the risk of a heart attack as they usually happen early in the morning.
How long do Infradian Rhythms last?
More than 24hours
What is the main example of an Infradian Rhythm?
The Menstrual Cycle (takes about 28 days from the womb lining shedding until the next period)
What is the basic outline of the Menstrual Cycle?
Ovulation
- oestrogen rises
- ovary develops and releases egg
Progesterone is produced
- thickens womb lining for pregnancy and implanation
Menstruation
- if the egg is not fertilised, it is absorbed into the body and carried out with the womb lining
Who researched Infradian Rhythms?
McClintock and Stern
What was the aim of McClintock and Stern?
To investigate an Exogenous Zeitgeber that may influence the Endogenous Pacemaker of the Menstrual Cycle
What was the procedure of McClintock and Stern?
- they studied the synchronisation of womens’ menstrual cycles using pheremones
- they used 29 women with irregular cycles
- they gathered pheromones from 9 of the women over 8 hours by placing a cotton pad under their armpits
- the pads were frozen, treated with alcohol, and wiped on the upper lip of the remaining 20 females
How many women were studied by McClintock and Stern?
29 women with irregular cycles
How many women had pheromones gathered by McClintock and Stern?
9
How many women received pheromones (McClintock and Stern)
20
What were McClintock and Stern’s findings?
68% of participants experienced changes in their menstrual cycles
Their cycles became closer to the woman’s who’s pheromones they had received
This supports the EZ in infradian rhythms
Evaluate Infradian Rhythms
Bad - McClintock and Stern may have had methodological issues
- there may be confounding variables such as stress, diet and exercise that also affected the cycles
- this may mean synchronisation happened by chance and results were flawed
Good - Menstrual Synchrony may be explained by natural selection and evolution
- there would have been an evolutionary advantage to synchronise cycles so pregnancies could also be synchronised
- this means that if something happened to one of the mothers, all the babies still had access to milk, which improved their chances of survival
- this suggests infradian rhythms have always had real world application, and synchronisation is an adaptive strategy
Good - Real World Application
- It has helped implement PhotoTherapy for people with Seasonal Affective Disorder (SAD)
- It is safer than antidepressants and is not addictive
- this suggests understanding infradian rhythms has useful medical applications
How long do Ultradian Rhythms last?
Less than 24 hours
What is the main example of Ultradian Rhythms?
The Stages of Sleep (last 90mins)
How long do the stages of sleep last?
- 90 min cycle
- Repeats throughout the night
How are the stages of sleep categorised?
Different levels of brainwave activity as monitored by EEGs
What are the stages of sleep?
Stages 1 and 2:
Light sleep
Stages 3 and 4:
Deep sleep/Slow Wave Sleep
Stage 5:
REM sleep (rapid eye movement)
What happens in Stages 1 and 2 of sleep?
- light sleep
- easily woken
- occasional sleep spindles (random changes in brain wave patterns)
- alpha waves - high frequency, short amplitude
What happens in Stages 3 and 4 of sleep?
- deep sleep/ slow wave sleep
- difficult to wake someone from
- delta waves have higher amplitude and low frequency
What happens in Stage 5 of sleep?
- Rapid Eye Movement (REM sleep)
- body is paralysed
- brain resembles awake activity
- dreams are often experienced
- theta waves are produced and eyes occasionally move
Who researched Ultradian Rhythms?
Dement and Kleitman
What was Dement and Kleitman’s procedure?
- they monitored electrical activity in the brains of 9 asleep participants using EEG recordings
- they woke the participants up during various stages of sleep
How many participants did Dement and Kleitman use?
9
How did Dement and Kleitman see the brain activity of their participants?
EEG recordings
What did Dement and Kleitman find?
- people woken up in REM reported dreams 90% of the time
- people woken up in nREM reported dreams 7% of the time
How many participants woken up in REM reported dreams (Dement and Kleitman)?
90%
How many participants woken up in NREM reported dreams (Dement and Kleitman)?
7%
Evaluate Ultradian Rhythms
Good - Lab Experiments
- used EEGs for high levels of control
- controlled temperature/lighting etc
- results should have high validity
Good - Research gives a better understanding of the real world
- research suggested Slow Wave Sleep reduces with age, and this deficit might explain other issues in old age, such as lack of alertness
- understanding this could lead to treatments and relaxation methods to help
- this means there are good practical values
Bad - Demand Characteristics
- Dement and Kleitman’s sample had to sleep in a lab setting with a skull cap and electrodes on
- they also knew they were being observed
- this could have made it uncomfortable for them to get to sleep, meaning their results were not a true reflection of their brain activity during the stages of sleep
What are Endogenous Pacemakers?
The internal body clocks that regulate our biological rhythms
What are 2 examples of Endogenous Pacemakers?
The Supraciasmatic Nucleus (SCN)
The Pineal Gland
What does the Suprachiasmatic Nucleus do?
It controls biological rhythms within our body by receiving information about light from the optic nerve, and adjusting our biological clocks so they are in time with the outside world
Where is the SCN located?
Above the Optic Chiasm
What is the SCN made up of?
The SCN is a cluster of nerve cells in our hypothalamus
What does the Pineal Gland do?
The SCN sends signals to the Pineal Gland about light
When light is sensed, melatonin is inhibited, so we wake up and are alert
When light is not sensed, melatonin is secreted, so we feel sleepy
What is melatonin?
Our sleep hormone
Who researched Endogenous Pacemakers? (x2)
Ralph et al –> hamsters
DeCoursey –> chipmunks
What did Ralph et al do?
They bred mutant hamsters that had abnormal circadian rhythms of 20 hours instead of 24
They implanted SCN neurons from these mutant hamsters into normal hamsters to see how much the SCN affected our biological rhythms
What did Ralph et al find?
The normal hamsters took on the 20hour cycles
This indicates the SCN plays an essential role in establishing and regulating circadian rhythms
What can Ralph et al’s findings also support?
EPs and Circadian Rhythms
What did DeCoursey do?
Destroyed SCN connections in 30 chipmunks
They returned them to the wild and observed them for 80 days
What did DeCoursey find?
The sleep/wake cycle had disappeared by the end of the study
A significant proportion were killed by predators as they were awake and vulnerable to attack when they should have been asleep
Evaluate Endogenous Pacemakers
Hint:
Isolation
Animal
Peripheral Oscillators
Bad - Can’t be studied in isolation
- EPs and EZs interact in everyday life, and it is impossible to completely isolate yourself from one or the other
- Siffre aimed to isolate himself from EZs, but he used a headlamp, which might have accidentally acted as an EZ (light)
- This suggests an interactionist approach should be used instead for a more comprehensive understanding
Good - Research support
Siffre
Ralph et al
DeCoursey
HOWEVER
Bad - Animal extrapolation (Ralph and DeCoursey)
Bad - There may be other body clocks
- Research has shown we have peripheral oscillators, which are circadian rhythms inside organs and cells
- They are influenced by the SCN but have also been found to act independently
- This could mean there are other complex influences on the sleep/wake cycle that we have not researched
What are Exogenous Zeitgebers?
External factors that reset our biological clocks through entrainment
What happens to our Endogenous Pacemakers without Exogenous Zeitgebers?
They become ‘free running’
What are 2 examples of Exogenous Zeitgebers?
Light
Social Cues
How is light an EZ?
It affects our sleep/wake cycle as we are entrained to our environment depending on light
How are Social Cues an EZ?
Mealtimes and social activities might determine what times we do things
Who researched Exogenous Zeitgebers?
Campbell and Murphy
What did Campbell and Murphy research?
Exogenous Zeitgebers:
Light can entrain our rhythms through skin receptors, without it reaching our eyes
What did Campbell and Murphy do?
They woke 15 participants up at various times
They shone a light on the back of their knees
What did Campbell and Murphy find?
Some participants had differences in their sleep cycles of up to 3 hours
This suggests light is always an EZ without the EP of the SCN
Evaluate Exogenous Zeitgebers
Hint:
Iceland
Age
Miles et al
Bad - There could be environmental factors
- In places with very little light in winter and very little darkness in summer (Iceland), people still have similar sleep/wake cycles all year round
- This suggests sleep/wake cycles are primarily controlled by EPs that can override environmental changes in light
Bad - Age related insomnia
- Research suggests people have poorer sleep as they age
- However, this could be due to EZs, as research found insomnia was improved with the increase of activity and light
- This makes it unclear whether EZs or EPs are more important
- Perhaps an interactionist approach would be more comprehensive
Bad - Case Study evidence challenges Campbell and Murphy
Miles et al
- Born blind
- Had circadian rhythm of 24.9
- No amount exposure to light or social cues has entrained or changed his cycle
- This contradicts Campbell and Murphy by suggesting light must enter the eyes, and EZs alone are not effective in resetting biological rhythms
What is the Case Study of Miles et al?
He was born blind
He had a circadian rhythm of 24.9hours
No amount of exposure to light or social cues has entrained or changed his cycle
Who does Miles et al contradict?
Campbell and Murphy
What can Miles et al be used for?
Contradicting Exogenous Zeitgebers being effective alone
