Bio Flashcards
1
Q
The emergence of psychology as a science
A
- By the beginning of the 20th century the scientific status and value of introspection was being questioned by many.
- John B Watson was very critical of introspection’s focus on the ‘private’ mental process.
-He believed that a truly scientific psychology should restrict itself to study phenomena that could be observed or measured.
-Behaviourists used controlled lab experiments which would dominate for the next 50 years.
2
Q
The nervous system
A
A specialised network of cells in the human body and is our primary internal communication system.
3
Q
The nervous systems 2 main functions
A
Two main functions:
1. To collect, process and respond to information in the environment.
2. To co-ordinate the working of different organs and cells in the body.
4
Q
What 2 sub sections can the nervous system be broken into
A
- Central Nervous System (CNS)
- Peripheral Nervous System (PNS)
5
Q
Brain
A
Centre of conscious awareness.
Highly-developed in humans.
Divided into two hemispheres.
Outer layer is called the cerebral cortex and is unique to mammals. It is like an orange peel and covers the brain.
6
Q
Spinal cord
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Extension of brain
Connects nerves to the PNS.
Controls reflex actions.
7
Q
Peripheral Nervous System
A
Transmits messages to and from the CNS via nerve cells.
8
Q
What 2 sub sections can the peripheral nervous system be broken into
A
Autonomic nervous system
Somatic nervous system
9
Q
Somatic Nervous System (SNS)
A
Receives information from sensory receptors and controls voluntary actions such as muscle movement.
10
Q
Autonomic Nervous System (ANS)
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Controls bodily functions e.g. breathing, heart rate, sexual arousal, stress.
11
Q
What 2 sub sections can the Autonomic nervous system be broken into
A
Sympathetic nervous system
Parasympathetic nervous system
12
Q
Sympathetic Nervous System
A
Controls the body’s response to perceived threats.
“Fight or Flight“
This responds to times of stress (sympathy!)
13
Q
Parasympathetic Nervous System
A
Regulates body functions while at rest.
“Rest and Digest“ or “Feed and Breed“
This is your normal state.
14
Q
The endocrine system
A
Works alongside the nervous system to control vital functions in the body.
It is another information system.
The endocrine system instructs glands to release hormones into the bloodstream.
These hormones are then carried to specific organs in the body via the bloodstream.
15
Q
Pituitary gland
A
This is the ‘master gland’ and is located in the brain. It controls the release of the hormones from all of the other endocrine glands in the body.
16
Q
Thyroid Gland
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Produces the hormone thyroxine which increases heart rate. It also increases metabolic rate which affects growth.
17
Q
Adrenal Gland
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Produces adrenaline in the adrenal medulla.
It triggers increased heart rate and contracting blood vessels, which creates physiological arousal for the fight or flight response.
18
Q
Ovaries and testes
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These are the female and male gland respectively.
Ovaries secrete oestrogen
Testes secrete testosterone
Both used for reproduction
19
Q
Endocrine and Autonomic Nervous System working together
A
The stressor causes your ANS to change from the Parasympathetic NS to the Sympathetic NS
The pituitary gland then releases adrenocorticotrophic (ACTH)
This hormone affects the adrenal glands causing it release adrenaline into the bloodstream.
This causes physiological changes in the body to occur eg. Increased heart rate.
Once the threat has passed the Parasympathetic NS returns the body to it’s resting state acting as a ‘brake’ to return to homeostasis.
20
Q
Neuron
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The basic building block of the nervous system, neurons are nerve cells that process and transmit messages through electrical and chemical signals
21
Q
Sensory neurons
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these carry messages from the PNS to the CNS. They have long dendrites and short axons
22
Q
Relay neurons
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these connect the sensory neurons to the motor or other relay neurons. They have short dendrites and short axons.
23
Q
Motor neurons
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These connect the CNS to the effectors such as muscles and glands. They have short dendrites and long axons
24
Q
The function of a neuron
A
there are 100 billion neurons in the human nervous system, 80% of which are located in the brain. By transmitting signals electrically and chemically,these neurons provide the nervous system with its primary means of communication.
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Types of neurons
Sensory
Relay
Motor
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Structure of neurons
neurons vary in size from less than a millimetre to up to a metre long, but all share the same basic building blocks.
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Cell body: (soma).
Includes a nucleus which contains the genetic material of the cell.
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Dendrites
Extend from the cell body and carry nerve impulses from other neurons towards the cell body.
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Axons
Carry the impulses away from the cell body down the length of the neuron.
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Myelin sheath
Covers the axon and is a fatty layer that protects the axon as well as speeding up the electrical transmission of the impulse. (The myelin sheath reminds me of sausages as it has gaps.)
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Nodes of Ranvier
Gaps which speed up transmission by forcing the impulse to jump across the gaps along the axon.
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Terminal buttons
Located at the end of the axon that communicates with the next neuron in the chain. The gap between the neurons known as a synapse.
33
The reflex arc
Reflex arcs are used as a short cut by the body. They involve the spinal cord rather than the brain and have evolved as a way to protect our self.
E.g if something is coming towards your eye you blink, These messages do not make it to the brain only the spinal cord.
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Electric transmission – the firing of a neuron
When a neuron is in a resting state, the inside of the cell is negatively charged in comparison to the outside.
When the neuron is activated by a stimulus, the inside of the cell (cell body) becomes positively charged, causing action potential.
This creates an electrical impulse to travel from the cell body, down the axon towards the end of the neuron.
35
Chemical transmission
Neurons communicate with each other within groups known as neural networks. (Separated by a tiny gap known as a synapse)
The synapse is between the terminal button one of neuron and the dendrite of another.
Signals within neurons are transmitted electrically (action potential), however signals between neurons are transmitted chemically in the synapse.
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synapse transmission
The axon carries the vesicle containing the neurotransmitter to the presynaptic nerve terminal.
The vesicle releases the neurotransmitter at the presynaptic neurons' membrane into the synapse.
The neurotransmitters diffuse across the synapse and binds to the receptor site on the post synaptic neurons membrane.
If the signal from the neurotransmitter is excitatory an electrical signal is generated (action potential) and passes along the neuron, if its inhibitory no action potential is generated.
Direction of travel of the chemical message can only be one way because of the structures in the pre and post synaptic membranes.
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Neurotransmitters
Each has its own specific molecular structure that fits into a post synaptic receptor site (like a lock and key). They all have their own specific functions.
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Excitation
a neurotransmitter (e.g. adrenaline) increases the positive charge of the postsynaptic neuron. This increases the likelihood that the neuron will fire and pass on the electrical impulse.
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Inhibition
a neurotransmitter (e.g. serotonin) increases the negative charge of the postsynaptic neuron. This decreases the likelihood that the neuron will fire and pass on the electrical impulse.
40
Summation
Whether a neuron fires or not is down to the overall net effect on the post synaptic neuron.
Many neurotransmitters are being released at once into the synapse, some excitatory and some inhibitory. It the overall charge on the post synaptic membrane that ‘decides’ if an action potential or not will be created.
41
Explain why neurons can only transmit information in one direction at a synapse.
-the synaptic vesicles containing the neurotransmitter are only present on / released from the presynaptic membrane
- the receptors for the neurotransmitters are only present on the postsynaptic membrane
- it is the binding of the neurotransmitter to the receptor which enables the signal / information to be passed / transmitted on (to the next neuron)
-diffusion of the neurotransmitters mean they can only go from high to low concentration, so can only travel from the presynaptic to the postsynaptic membrane.
42
Localisation of function
The theory that different areas of the brain are responsible for specific behaviours, processes or activities.
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What are the hemispheres of the brain
-the brain is divided into 2 hemispheres
-activity on the right side of the body is controlled by the left side of the brain and vice versa
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cerebral cortex
-the outer layer of both hemispheres
-responsible for higher level processing
-human cortex's are more developed than other animals
-it's grey due to the location of cell bodies
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Frontal lobe-motor area
Voluntary movement in opposite side of the body (damage to this area of the brain may result in a loss of control over fine movements
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Parietal lobe- somatosensory lobe
-where sensory information from the skin is represented
-the amount of somatosensory area devoted to a particular body part denotes its sensitivity
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Occipital lobe- visual area
Each eye sends info from the right visual field to the left visual cortex and vice versa
(damage in a visual cortex can produce blindness in the opposite visual field)
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Temporal lobe-auditory area
Analyses speech
(damage may produce hearing loss or the ability to comprehend languages)
49
What hemisphere is language restricted to
left
50
Broca's area
-identified a small region in the left frontal lobe responsible for speech production
-Damage to the area causes Broca's aphasia
-Slow speech, laborious and lacking in fluency
51
Wernicke's area
-Identified a region in the left temporal lobe responsible for language comprehension
-Damage to this area causes Wernicke's aphasia
-Producing nonsense words as part of their speech
52
The case of Phineas gage
-preparing to blast a section of rock when he dropped his tampering iron which caused the explosive to ignite
-This caused a metre length pole through Gages pre frontal cortex which exited his skull from the top of his head taking a portion of his brain out
-He survived the damage to his brain, the only mark being on his personality
- Went from calm and reserved to quick tempered
53
What is a strength of localization (evidence from neurosurgery)
One strength of localisation theory is that damage to areas of the brain has been linked to mental disorders. Neurosurgery (surgery on the brain) is a last resort method for treating some mental disorders, targeting specific areas of the brain which may be be involved. For example, cingulotomy involves isolating a region called the cingulate gyrus which has been implicated in OCD. Dougherty et al. (2002) reported on 44 people with OCD who had undergone a cingulotomy. At post-surgical follow-up after 32 weeks, about 30% had met the criteria for successful response to the surgery and 14% for partial response. The success of these procedures suggests that behaviours associated with serious mental disorders may be localised.
54
What is a strength of localisation (evidence from brain scans)
Another strength is evidence from brain scans that supports the idea that many everyday brain functions are localised.
for instance, Petersen et al. (1988) used brain scans to demonstrate how Wernicke's area was active during a listening task and Broca's area was active during a reading task. Also, a review of long-term memory studies by Buckner and Petersen (1996) revealed that semantic and episodic memories reside in different parts of the prefrontal cortex. These studies confirm localised areas for everyday behaviours.
Therefore objective methods for measuring brain activity have provided sound scientific evidence that many brain functions are localised.
55
What is a counterpoint of evidence of brain scans for localisation
A challenge to localisation theory comes from the work of Lashley (1950). Lashley removed areas of the cortex (between 10% and 50%) in rats that were learning the route through a maze. No area was proven to be more important than any other area in terms of the rats' ability to learn the route. The process of learning seemed to require every part of the cortex rather than being confined to a particular area. This suggests that higher cognitive processes, such as learning, are not localised but distributed in a more holistic way in the brain.
56
What is a limitation of localisation (language localisation questioned)
One limitation is that language may not be localised just to Broca's and Wernicke's areas. A recent review by Dick and Tremblay (2016) found that only 2% of modern researchers think that language in the brain is completely controlled by Broca's and Wernicke's areas. Advances in brain imaging techniques, such as fMRI, mean that neural processes in the brain can be studied with more clarity than ever before. It seems that language function is distributed far more holistically in the brain than was first thought. So-called language streams have been identified across the cortex, including brain regions in the right hemisphere, as well as subcortical regions such as the thalamus. This suggests that, rather than being confined to a couple of key areas, language may be organised more holistically in the brain, which contradicts localisation theory.
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laterlisation
The idea that the two hemispheres of the brain are functionally different and that certain mental processes and behaviours are mainly controlled by one hemisphere
58
How is language both localised and laterlised
-only in the left hemisphere
-Broca's area/Wernicke's area
-however the right hemisphere can produce rudimentary words and contribute to emotional context
-LH - analyser
-RH- synthesiser
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Contralateral wiring
The brain in some cases is cross wired. In the motor area the right hemisphere controls movement on the left side of the body and vice versa
60
How does contralateral wiring work in vision
-contralateral and ipsilateral
-each eye receives information from the left visual field and right
-the left visual field is connected to the right hemisphere and vice versa (aids depth perception)
61
What is a strength of hemispheric lateralisation (lateralisation in the connected brain)
-One strength is research showing that even in connected brains the two hemispheres process information differently.
-E.g, Fink et al. (1996) used PET scans to identify which brain areas were active during a visual processing task. When participants with connected brains were asked to attend to global elements of an image (such as looking at a picture of a whole forest) regions of the RH were much more active. When required to focus in on the finer detail (such as individual trees) the specific areas of the LH tended to dominate.
-This suggests that, at least as far as visual processing is concerned, hemispheric lateralisation is a feature of the connected brain as well as the split-brain.
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What is a limitation of hemispheric lateralisation (one brain)
-One limitation is the idea that the LH as analyser and RH as synthesiser may be wrong.
-There may be different functions in the RH and LH, but research suggests people do not have a dominant side of their brain which creates a different personality.
-Nielsen et al. (2013) analysed brain scans from over 1000 people aged 7 to 29 years and did find that people used certain hemispheres for certain tasks (evidence for lateralisation). But there was no evidence of a dominant side, i.e. not artist's brain or mathematician's brain.
-This suggests that the notion of right- or left-brained people is wrong.
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Split-brain research
A series of studies that began in the 1960s involving people with epilepsy who had experienced a surgical separation of the hemispheres of their brain to reduce the severity of their epilepsy. This enabled researchers to test lateral functions of the brain in isolation
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Split brain operation
severing the connections between the RH and the LH (corpus callosum)
-During an epileptic seizure excessive electrical activity travels from one hemisphere to the other
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Sperry's procedure
-Eleven people who had a split-brain operation were studied
-an image could be projected to a participant's RVF (processed by the LH) and the same, or different, image could be projected to the LVF (processed by the RH). -In the 'normal' brain, the corpus callosum would immediately share the information between both hemispheres giving a complete picture of the visual world.
-However, presenting the image to one hemisphere of a split-brain participant meant that the information cannot be conveyed from that hemisphere to the other.
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Sperry's Findings
-When a picture of an object was shown to a participant's RVF (linked to LH), the participant could describe what was seen.
-But they could not do this if the object was shown to the LVF (RH) - they said there was 'nothing there'. This is because, in the connected brain, messages from the RH are relayed to the language centres in the LH.
-Although participants could not give verbal labels to objects projected to the LVF, they could select a matching object out of sight using their left hand (linked to RH). The left hand was also able to select an object that was most closely associated with an object presented to the LVF (for instance, an ashtray was selected in response to a picture of a cigarette).
-If a pinup picture was shown to the LVF there was an emotional reaction (e.g. a giggle) but the participants usually reported seeing nothing or just a flash of light.
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Sperry's conclusion
These observations show how certain functions are lateralised in the brain and support the view that the LH is verbal and the RH is 'silent' but emotional.
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What is a strength of split brain research (research support)
One strength is support from more recent split-brain research. Gazzaniga (Luck et al. 1989) showed that split-brain participants actually perform better than connected controls on certain tasks. For example, they were faster at identifying the odd one out in an array of similar objects than normal controls. In the normal brain, the LH's better cognitive strategies are 'watered down' by the inferior RH (Kingstone et al. 1995). This supports Sperry's earlier findings that the 'left brain' and right brain' are distinct.
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What is a limitation of split-brain research (Generalisation issues)
One limitation of Sperry's research is that causal relationships are hard to establish.
The behaviour of Sperry's split-brain participants was compared to a neurotypical control group. An issue though is that none of the participants in the control group had epilepsy. This is a major confounding variable. Any differences that were observed between the two groups may be the result of the epilepsy rather than the split brain. This means that some of the unique features of the split-brain participants' cognitive abilities might have been due to their epilepsy (though Fink's research, above, supports Sperry's conclusions).
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Plasticity
the tendency for the brain to change and adapt as a result of experience and learning
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Synaptic pruning
As we age rarely used connections are deleted and frequently used ones are strengthened
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What did Gopnik suggest about brain plasticity
there is a rapid growth in the number of synaptic connections in infancy which peaks at approx' 15,000 at age 2-3 which is twice as many as in the adult brain
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Research into brain plasticity
-Maguire et al. (2000) studied the brains of London taxi drivers and found significantly more volume of grey matter in the posterior hippocampus than in a matched control group.
-This part of the brain is associated with the development of spatial and navigational skills in humans and other animals.
-As part of their training, London cabbies must take a complex test called The Knowledge, which assesses their recall of the city streets and possible routes.
-Maguire et al. found that this learning experience alters the structure of the taxi drivers' brains. They also found that the longer the taxi drivers had been in the job, the more pronounced was the structural difference.
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What is a limitation of brain plasticity (negative plasticity)
-One limitation of plasticity is that it may have negative behavioural consequences.
-Evidence has shown that the brain's adaptation to prolonged drug use leads to poorer cognitive functioning in later life, as well as an increased risk of dementia (Medina et al. 2007).
-Also, 60-80% of amputees have been known to develop phantom limb syndrome the continued experience of sensations in the missing limb as if it were still there. -These sensations are usually unpleasant, painful and are thought to be due to cortical reorganisation in the somatosensory cortex that occurs as a result of limb loss (Ramachandran and Hirstein 1998).
-This suggests that the brain's ability to adapt to damage is not always beneficial.
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What is a strength of brain plasticity (age and plasticity)
-One strength is that brain plasticity may be a life-long ability.
-In general plasticity reduces with age. However, Bezzola et al. (2012) demonstrated how 40 hours of golf training produced changes in the neural representations of movement in participants aged 40-60.
-Using fMRI, the researchers observed increased motor cortex activity in the novice golfers compared to a control group, suggesting more efficient neural representations after training.
-This shows that neural plasticity can continue throughout the lifespan.
76
Functional recovery
A form of plasticity. Following damage through trauma, the brain's ability to redistribute or transfer functions usually performed by a damaged area(s) to other, undamaged area(s).
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Critical period for adults for brain plasticity
-once believed that when an adults brain was developed, plasticity would not be possible as it had gone past the critical period of development
-However more recent research suggests that any time in life existing neural connections can change or new neural connections can be formed as a result of learning
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What is functional plasticity an example of
neural plasticity
79
spontaneous vs slow recovery
-redistribution can quickly occur after trauma (spontaneous recovery) but then slow down after several weeks/months
-People may need rehabilitation therapy to further their recovery
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What happens in the brain during recovery
-the brain rewires and reorganises itself by making new synaptic connections
-neural pathways that would not normally be used to carry out certain functions are activated (unmasked) to allow functions to carry on in the same way as before
81
What are structural changes that occur in the brain during recovery
-axonal sprouting
-denervation super sensitivity
-recruitment of homologous areas
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Axonal sprouting
The growth of new nerve endings which connect with other undamaged nerve cells to form new neuronal pathways
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Denervation super sensitivity
This occurs when axons that do similar jobs become aroused to a higher level to compromise for the ones that are lost
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Recruitment of homologous areas on the opposite side of the brain
Specific tasks can still be performed.
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What is a strength of functional recovery (real-world application)
-One strength of functional recovery research is its real-world application.
-Understanding the processes involved in plasticity has contributed to the field of neurorehabilitation. Simply understanding that axonal growth is possible encourages new therapies to be tried.
-E.g constraint-induced movement therapy is used with stroke patients whereby they repeatedly practise using the affected part of their body (such as an arm) while the unaffected arm is restrained.
This shows that research into functional recovery is useful as it helps medical professionals know when interventions need to be made.
86
What is a limitation of functional recovery (cognitive reserve)
-One limitation of functional recovery is that level of education may influence recovery rates.
-Schneider et al. (2014) revealed that the more time people with a brain injury had spent in education - taken as an indication of their 'cognitive reserve' - the greater their chances of a disability-free recovery (DFR). -40% of those who achieved DFR had more than 16 years' education compared to about 10% of those who had less than 12 years' education.
-This would imply that people with brain damage who have insufficient DFR are less likely to achieve a full recovery.
87
Functional magnetic resonance imaging
-works by detecting the changes in both blood oxygenation and flow that occur as a result of neural activity in specific parts of the brain.
-When a brain area is more active it consumes more oxygen and to meet this increased demand, blood flow is directed to the active area.
-fMRI produces three-dimensional images (activation maps) showing which parts of the brain are involved in a particular mental process
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Strengths of Functional magnetic resonance imaging
-Doesn't not rely on the use of radiation. If administered correctly it is virtually risk-free, non-invasive and straightforward to use. It also produces images that have very high spatial resolution, depicting detail by the millimetre, and providing a clear picture of how brain activity is localised. This means that fMRI can safely provide a clear picture of brain activity.
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Limitations of Functional magnetic resonance imaging
expensive compared to other neuroimaging techniques. It has poor temporal resolution because there is around a 5-second time-lag behind the image on screen and the initial firing of neuronal activity. This means fMRI may not truly represent moment-to-moment brain activity.
90
Electroencephalogram (EEG)
-measures electrical activity within the brain via electrodes that are fixed to an individual's scalp using a skull cap.
-The scan recording represents the brainwave patterns that are generated from the action of thousands of neurons, providing an overall account of brain activity.
-EEG is often used by clinicians as a diagnostic tool as unusual arrhythmic patterns of activity may indicate neurological abnormalities such as epilepsy, tumours or some sleep disorders.
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Strengths of Electroencephalogram (EEG)
EEG has been useful in studying the stages of sleep and in the diagnosis of conditions such as epilepsy, a disorder characterised by random bursts of activity in the brain that can easily be detected on screen. high temporal resolution.
Today's EEG technology can accurately detect brain activity at a resolution of a single millisecond (and even less in some cases). This shows the real-world usefulness of the technique.
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Limitations of Electroencephalogram (EEG)
The main drawback of EEG lies in the generalised nature of the information received (that of many thousands of neurons). The EEG signal is also not useful for pinpointing the exact source of neural activity. Therefore it does not allow researchers to distinguish between activities originating in different but adjacent locations.
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Event-related potentials
-EEG in its raw form it is a overly general measure of brain activity. However, within EEG data are contained all the neural responses associated with specific sensory, cognitive and motor events that may be of interest to cognitive neuroscientists.
-researchers have developed a way of teasing out and isolating these responses. -Using a statistical averaging technique, all extraneous brain activity is filtered out leaving only those responses that relate to, say, the presentation of a specific stimulus or performance of a specific task.
-What remains are event-related potentials (ERPs) - types of brainwave that are triggered by particular events.
Research has revealed many different forms of ERP and how, for example, these are linked to cognitive processes such as attention and perception.
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Strengths of Event-related potentials
The limitations of EEG are partly addressed through the use of ERPs. These bring much more specificity to the measurement of neural processes than could ever be achieved using raw EEG data. As ERPs are derived from EEG measurements, they have excellent temporal resolution, especially when compared to neuroimaging techniques such as fMRI. This means that ERPs are frequently used to measure cognitive functions and deficits such as the allocation of attentional resources and the maintenance of working memory.
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Limitations of Event-related potentials
Critics have pointed to a lack of standardisation in ERP methodology between different research studies which makes it difficult to confirm findings. A further issue is that, in order to establish pure data in ERP studies, background 'noise' and extraneous material must be completely eliminated. This is a problem because it may not always be easy to achieve.
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Post mortem examinations
This is a technique involving the analysis of a person's brain following their death.
In psychological research, individuals whose brains are subject to a post-mortem examination are likely to be those who have a rare disorder and have experienced unusual deficits in cognitive processes or behaviour during their lifetime. Areas of damage within the brain are examined after death as a means of establishing the likely cause of the affliction the person experienced. This may also involve comparison with a neurotypical brain in order to ascertain the extent of the difference.
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strengths of Post mortem examinations
Post-mortem evidence was vital in providing a foundation for early understanding of key processes in the brain. Broca and Wernicke both relied on post-mortem studies in establishing links between language, brain and behaviour decades before neuroimaging ever became a possibility. Post-mortem studies were also used to study HM's brain to identify the areas of damage, which could then be associated with his memory deficits. This means post-mortems continue to provide useful information.
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limitations of Post mortem examinations
Causation is an issue within these studies, however. Observed damage to the brain may not be linked to the deficits under review but to some other unrelated trauma or decay. A further problem is that postmortem studies raise ethical issues of consent from the individual before death. Participants may not be able to provide informed consent, for example in the case of HM who lost his ability to form memories and was not able to provide such consent - nevertheless post-mortem research has been conducted on his brain. This challenges the usefulness of post-mortem studies in psychological research.
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Biological rhythms
Distinct patterns of changes in body activity that conform to cyclical time periods. Biological rhythms are influenced by internal body clocks (endogenous pacemakers) as well as external changes to the environment (exogenous zeitgebers).
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Circadian rhythms
Biological rhythms, subject to a 24-hour cycle, which regulate a number of body processes such as the sleep/wake cycle and changes in core body temperature.
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What is the sleep/wake cycle governed by
daylight- exogenous zeitgeber
suprachiasmatic nucleus- endogenous pacemaker
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Siffre's cave study
-spent several extended periods underground to study the effects on his own biological rhythms.
-Deprived of exposure to natural light and sound, but with access to adequate food and drink, resurfaced in mid-September after two months in the caves of the Southern Alps believing it to be mid-August! -A decade later he performed a similar feat but this time for six months in a Texan cave.
-In each case, his 'free-running' biological rhythm settled down to one that was just beyond the usual 24 hours (around 25 hours) though he did continue to fall asleep and wake up on a regular schedule.
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Aschoff and Wever
Similar results were recorded by Aschoff and Wever (1976) who convinced a group of participants to spend four weeks in a World War 2 bunker deprived of natural light. All but one of the participants (whose sleep/wake cycle extended to 29 hours) displayed a circadian rhythm between 24 and 25 hours. Both Siffre's experience and the bunker study suggest that the 'natural' sleep/wake cycle may be slightly longer than 24 hours but that it is entrained by exogenous zeitgebers associated with our 24-hour day (such as the number of daylight hours, typical mealtimes, etc.).
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Folkard
-Folkard et al. (1985) studied a group of 12 people who agreed to live in a dark cave for three weeks, retiring to bed when the clock said 11.45 pm and rising when it said 7.45 am. Over the course of the study, the researchers gradually speeded up the clock (unbeknown to the participants) so an apparent 24-hour day eventually lasted only 22 hours!
It was revealed that only one of the participants was able to comfortably adjust to the new regime. This would suggest the existence of a strong free-running circadian rhythm that cannot easily be overridden by exogenous zeitgebers.
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What is a strength of research into circadian rhythms (shift work)
-One strength of research into circadian rhythms is that it provides an understanding of the adverse consequences that occur when they are disrupted.
-E.g, night workers engaged in shift work experience a period of reduced concentration around 6 in the morning (a circadian trough) meaning mistakes and accidents are more likely (Boivin et al. 1996). -Research has also pointed to a relationship between shift work and poor health - shift workers are three times more likely to develop heart disease than people who work more typical work patterns (Knutsson 2003).
-This shows that research into the sleep/wake cycle may have real-world economic implications in terms of how best to manage worker productivity.
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What is a limitation of research into circadian rhythms (Individual differences)
-One limitation of research into circadian rhythms is that generalisations are difficult to make.
-The studies described on the facing page are based on very small samples of participants. It seems that sleep/wake cycles may vary widely from person to person.
-Research by Czeisler et al. (1999) found individual differences in sleep/wake cycles varying from 13 to 65 hours. In addition, a study by Duffy et al. (2001) revealed that some people have a natural preference for going to bed early and rising early (known as larks) whereas others prefer the opposite (owls). Even Siffre, in a later 1999 study, observed that his own sleep/wake cycle had slowed down since he was a young man.
-This means that it is difficult to use the research data to discuss anything more than averages, which may be meaningless.
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What is a strength of research into circadian rhythms (medical treatment)
-Another strength of research into circadian rhythms is that it has been used to improve medical treatments.
-Circadian rhythms co-ordinate a number of the body's basic processes such as heart rate, digestion and hormone levels. These rise and fall during the course of a day which has led to the field of chronotherapeutics - how medical treatment can be administered in a way that corresponds to a person's biological rhythms.
-E.g aspirin as a treatment for heart attacks is most effective if taken last thing at night.
Aspirin reduces blood platelet activity and this can reduce the risk of heart attack.
Heart attacks are most likely to occur early in the morning, so the timing of taking aspirin matters.
-This shows that circadian rhythm research can help increase the effectiveness of drug treatments.
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What is a counterpoint of shift work for research into circadian rhythms
However, studies investigating the effects of shift work tend to use correlational methods. This means it is difficult to establish whether desynchronisation of the sleep/wake cycle is actually a cause of negative effects.
There may be other factors. E.g, Solomon (1993) concluded that high divorce rates in shift workers might be due to the strain of deprived sleep and other influences such as missing out on important family events.
This suggests that it may not be biological factors that create the adverse consequences associated with shift work.
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suprachiasmatic nucleus
lies above the optic chiasm so provides information from the eye about light.
Sends messages to the pineal gland about light levels
-If light levels are low the pineal gland releases melatonin and we feel sleepy
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Infradian rhythms
A type of biological rhythm with a frequency of less than one cycle in 24 hours, such as menstruation and seasonal affective disorder.
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Ultradian rhythms
A type of biological rhythm with a frequency of more than one cycle in 24 hours, such as the stages of sleep (the sleep cycle).
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Menstrual cycle
-governed by monthly hormone levels which regulate ovulation
-typically takes 28 days
-rising levels of oestrogen cause the ovary to develop an egg and release it
-progesterone makes the womb lining grow thicker ready for an egg
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Stem and Mclintock
Stern and McClintock studied 29 women with a history of irregular periods.
Samples of pheromones were gathered from nine of the women at different stages of their menstrual cycles, via a cotton pad placed in their armpit.
-The pads were worn for at least 8 hours to ensure that pheromones were picked up. The pads were treated with alcohol and frozen, to be rubbed on the upper lip of the other participants.
-On day one, pads from the start of the menstrual cycle were applied to all 20 women, on day two they were all given a pad from the second day of the cycle, and so on.
-Stern and McClintock found that 68% of women experienced changes to their cycle which brought them closer to the cycle of their 'odour donor.
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seasonal affective disorder (SAD)
-depressive disorder which has a seasonal pattern of onset, and is described and diagnosed as a mental disorder in DSM-5. -As with other forms of depression, the main symptoms of SAD are persistent low mood alongside a general lack of activity and interest in life.
-SAD is often referred to as the winter blues as the symptoms are triggered during the winter months when the number of daylight hours becomes shorter.
-SAD is a particular type of infradian rhythm called a circannual rhythm as it is subject to a yearly cycle. However, it can also be classed as a circadian rhythm as the experience of SAD may be due to the disruption of the sleep/wake cycle and this can be attributed to prolonged periods of daily darkness during winter.
-Psychologists have hypothesised that the hormone melatonin is implicated in the cause of SAD. During the night, the pineal gland secretes melatonin until dawn when there is an increase in light. During winter, the lack of light in the morning means this secretion process continues for longer. This is thought to have a knock-on effect on the production of serotonin in the brain - a chemical that has been linked to the onset of depressive symptoms.
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stages of sleep
five distinct stages of sleep that altogether span approximately 90 minutes - a cycle that continues throughout the course of the night. Each of these stages is characterised by a different level of brainwave activity which can be monitored using an EEG
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What is a strength of infradian rhythms (evolutionary basis)
-One strength of menstrual synchrony research is that it may be explained by natural selection.
-Synchronisation of the menstrual cycle, of the kind observed in the Stern and McClintock study, is thought by some to have evolutionary value. For our distant ancestors it may have been advantageous for women to menstruate together and become pregnant at the same time.
-In a social group, this would allow babies who had lost their mothers during or after childbirth to have access to breast milk, thereby improving their chances of survival.
-This suggests that synchronisation is an adaptive strategy.
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What is a limitation of infradian rhythms (methodological limitations)
-One limitation of synchronisation studies is their methodological shortcomings.
-There are many factors that may effect change to the menstrual cycle, including stress, changes in diet, exercise, etc.
-These may act as confounding variables, which means that any supposed pattern of synchronisation is no more than would have been expected to occur by chance. This may explain why other studies (e.g. Trevathan et al. 1993) have failed to replicate the findings.
-This suggests that menstrual synchrony studies are flawed.
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What is a strength of ultradian rhythms (improved understanding)
-One strength of research into ultradian rhythms is that it has improved understanding of age-related changes in sleep.
-Sleep scientists have observed that SWS reduces with age. Growth hormone is mostly produced during SWS therefore this is reduced in older people. According to Cauter et al. (2000), the resulting sleep deficit may explain various issues in old age, such as reduced alertness. In order to increase SWS, relaxation and medication may be used.
-This suggests that knowledge of ultradian rhythms has practical value.
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What is a limitation of ultradian rhythms (individual differences)
-One limitation of ultradian rhythms research is there is significant variation between people.
-Tucker et al. (2007) found large differences between participants in terms of the duration of each sleep stage, particularly stages 3 and 4.
-Tucker et al. suggest that these differences are likely to be biologically determined.
This makes it difficult to describe 'normal sleep' in any meaningful way.
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What are the 5 stages of sleep
Stages 1 and 2- This is light sleep a person may be easily woken. In stage 1, brain waves are high frequency and have a short amplitude. These are alpha waves. In stage 2, the alpha waves continue but there are occasional random changes in pattern called sleep spindles.
Stages 3 and 4- This is known as deep sleep or slow wave sleep. The brain waves are delta waves with lower frequency and higher amplitude. It is difficult to wake someone at this point.
Stage 5 (REM sleep)- The body is paralysed yet brain activity closely resembles that of the awake brain. During this time, the brain produces theta waves and the eyes occasionally move around, thus rapid eye movement. Dreams are most often experienced during REM sleep, but may also occur in deep sleep.
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Endogenous pacemakers
Internal body clocks that regulate many of our biological rhythms, such as the influence of the suprachiasmatic nucleus (SCN) on the sleep/wake cycle.
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Exogenous zeitgebers
External factors that affect or entrain our biological rhythms, such as the influence of light on the sleep/wake cycle.
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where is the suprachiasmatic nucleus found
Hypothalamus in both hemispheres
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Decoursey
The influence of the SCN has been demonstrated in studies involving animals. DeCoursey et al. (2000) destroyed the SCN connections in the brains of 30 chipmunks who were then returned to their natural habitat and observed for 80 days. The sleep/wake cycle of the chipmunks disappeared and by the end of the study a significant proportion of them had been killed by predators (presumably because they were awake, active and vulnerable to attack when they should have been asleep).
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What is a limitation of SCN research (beyond the master clock)
-One limitation of SCN research is that it may obscure other body clocks.
-Research has revealed that there are numerous circadian rhythms in many organs and cells in the body. These peripheral oscillators are found in the organs including the lungs, pancreas and skin.
-They are influenced by the actions of the SCN, but also act independently. Damiola et al. (2000) demonstrated how changing feeding patterns in mice could alter the circadian rhythms of cells in the liver by up to 12 hours, whilst leaving the rhythm of the SCN unaffected.
-This suggests other complex influences on the sleep/wake cycle.
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What is a limitation of SCN research (interactionist system)
-Another limitation is that endogenous pacemakers cannot be studied in isolation.
Total isolation studies, are extremely rare.
-Remember also that Siffre made use of artificial light which could have reset his biological clock every time he turned his lamp on.
-In everyday life, pacemakers and zeitgebers interact, and it may make little sense to separate the two for the purpose of research.
-This suggests the more researchers attempt to isolate the influence of internal pacemakers, the lower the validity of the research.
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Ralph
In another study, Ralph et al. (1990) bred 'mutant' hamsters with a 20-hour sleep/wake cycle.
When SCN cells from the foetal tissue of mutant hamsters were transplanted into the brains of normal hamsters, the cycles of the second group defaulted to 20 hours.
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Light as an exogenous zeitgeber
-It can reset the body's main endogenous pacemaker, the SCN, and thus plays a role in the maintenance of the sleep/wake cycle. -Light also has an indirect influence on key processes in the body that control such functions as hormone secretion and blood circulation.
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social cues as an exogenous zeitgeber
-new born babies' initial sleep/wake cycle is pretty much random. At about 6 weeks of age, the circadian rhythms begin and, by about 16 weeks, babies' rhythms have been entrained by the schedules imposed by parents, including adult-determined mealtimes and bedtimes.
-Research on jet lag suggests that adapting to local times for eating and sleeping (rather than responding to one's own feelings of hunger and fatigue) is an effective way of entraining circadian rhythms and beating jet lag when travelling long distances.
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What is a limitation of exogenous zeitgeber (environmental observations)
-One limitation is that exogenous zeitgebers do not have the same effect in all environments.
-The experience of people who live in places where there is very little darkness in summer and very little light in winter tell a different story from the usual narrative. For instance, people who live within the Arctic Circle have similar sleep patterns all-year round, despite spending around six months in almost total darkness.
-This suggests the sleep/wake cycle is primarily controlled by endogenous pacemakers that can override environmental changes in light.
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What is a limitation of exogenous zeitgeber (case study evidence)
Another limitation is evidence challenges the role of exogneous zeitgebers Miles et al. (1977) recount the study of a young man, blind from birth, who had an abnormal circadian rhythm of 24.9 hours. Despite exposure to social cues, such as regular mealtimes, his sleep/wake cycle could not be adjusted. This suggests that social cues alone are not effective in resetting the biological rhythm.
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Campbell and Murphy study on light
-Campbell and Murphy demonstrated that light may be detected by skin receptor sites on the body even when the same information is not received by the eyes.
-Fifteen participants were woken at various times and a light pad was shone on the back of their knees. The researchers managed to produce a deviation in the participants' usual sleep/wake cycle of up to three hours in some cases!
-This suggests that light is a powerful exogenous zeitgeber that need not necessarily rely on the eyes to exert its influence on the brain.
