BP - Ways of investigating the brain Flashcards
1
Q
Why investigate the brain?
A
Allows us to investigate a range of brain activity and better understand what is happening in the brain during activities and response to stimulus.
- Some techniques record global neural activity, others hone in on activity in specific parts of the brain as it performs certain tasks or processes
- Others involve studying sections of a deceased brain to investigate anatomical reasons for behaviour observed whilst the patient was alive
2
Q
What is an fMRI?
A
Functional Magnetic Resonance Imaging - function
- Measures changes in brain activity whilst a person performs a task, by measuring changes in blood flow in particular areas of the brain using magnetic fields and radio waves which indicates increased neural activity in those areas
- When a brain area becomes more active, it consumes more oxygen and to meet increased demand, blood flow increases to the active area to deliver oxygen to the red blood cells (haemodynamic response) and the amount of OB in that part of the brain therefore changes and that has a magnetic signature detectable by the fMRI
- Radio waves can also be used to reorient hydrogen atoms in the brain and the speed at which they return to their original position can also measure the amount of OB in that part of the brain, allowing researchers to map the brain areas involved in a particular mental activity
- Activity in regions of interest can be compared with a baseline task followed by a specific activity and the resulting fMRI data can be used to identify brain areas where there is matching pattern of change, concluding that the areas were activated by that stimulus e.g. looking at a visual stimulus for 30 seconds and have 30 seconds of eyes shut as a control state
3
Q
What is an EEG?
A
Measures electrical activity in the brain by placing electrodes on the scalp with a skull cap and detecting small electrical changes resulting from neuronal activity directly below where they are placed. They directly measure the activity of neurons. - function
- Differing numbers of electrodes can be used depending on the focus of the research
- The scan recording represents the brainwave patterns that are generated from the action of millions of neurons, providing an overall account of brain activity and therefore records general brain activity
- Links to states of sleep and arousal
- Often used as a diagnostic tool, as unusual arrhythmic patterns of activity which may indicate neurological abnormalities such as epilepsy, tumours, Alzheimer’s disease or disorders of sleep
- e.g. recordings can show that epileptic patients have spikes of electrical activity
- EEG patterns in patients with brain disease and brain injury show a slowing of electrical activity overall
4
Q
What is an ERP?
A
Event-related potentials - function
- Responses that relate to a specific stimulus that is presented to the participant, where the psychologists looks for activity related specifically to a stimulus
- It is a more specific version of an EEG, being specific to one activity not the whole brain’s electrical activity
- To filter out extraneous brain activity, many versions of a stimulus are presented and then responses are averaged together to find the consistent activity related to the stimulus
- Measured brain function response as a result of a specific sensory, cognitive or motor event
- Measures the neuronal activity of a specific stimulus
5
Q
What is a post-mortem examination?
A
Structure of the brain - technique involving the analysis of a person’s brain following their death
- In psychological research, individuals whose brains are subject to these examinations are likely to be those who have a rare disorder and have experienced unusual deficits in mental processes or behaviour during their lifetime
- Areas of damage in the brain are examined after death to try to correlate structural abnormalities and damage to behaviour
- This may also involve comparison with a neurotypical brain in order to ascertain the extent of the difference
6
Q
What is spatial resolution?
A
- The smallest feature or structure that a scanner can detect and is an important feature in brain scanning techniques
- Greater spatial resolution allows psychologists to discriminate between different brain regions with greater accuracy
- fMRI - high SR of approx. 1-2mm that allows regional activity to be determined with greater accuracy
- EEG and ERP - low SR
7
Q
What is temporal resolution?
A
- The accuracy of a scanner in relation to time - how quickly it can detect changes in brain activity
- As a result, low TR means that there is delayed recording in brain activity and it is hard to predict activity
- fMRI - low TR - 1-4 seconds, much slower than other methods
- EEG and ERP - high TR, taking readings every millisecond and can therefore record brain activity in real time creating accurate measurements of electrical activity when undertaking specific tasks
8
Q
EEG cont.
A
There are four types of EEG patterns including alpha waves, beta waves, theta waves and delta waves.
Each of these patterns has two basic properties that psychologists can examine:
1. Amplitude: the intensity or size of the activity
2. Frequency: the speed or quantity of activity
- Also, EEG patterns produce two distinctive states: synchronised and desynchronized patterns. A synchronised pattern is where a recognised waveform
(alpha, beta, delta and theta) can be detected, whereas a desynchronized is where no pattern can be detected.
- Fast desynchronized patterns are usually found when awake and synchronised patterns are typically found during sleep (alpha waves are associated with light
sleep, and theta/delta waves are associated with deep sleep)
- Furthermore, EEG scanning was responsible for developing our understanding of REM (dream) sleep,
which is associated with a fast, desynchronized activity, indicative of dreaming.
9
Q
Evaluation of fMRI - Strengths
A
- Captures dynamic brain activity, as opposed to techniques which just show structure
- Advantageous to investigate brain activity in humans rather than generalising from animal lesion / single electrode recording studies - less valid and ethical
- Unlike other techniques, it doesn’t rely on radiation and so is virtually risk free, non-invasive and straightforward to use
- Produces images with high spatial resolution, close to a mm, and provides a clear picture of how brain activity is localised
- Offers a more objective and reliable measure of psychological processes than is possible with verbal reports, and is therefore useful as a way of investigating psychological phenomena people could not give insight to verbally
10
Q
Evaluation of fMRI - Weaknesses
A
- Research is expensive when compared to other techniques, leading to reduced sample sizes which negatively impact validity and additionally it can only capture a clear image if the person stays perfectly still
- Because it measures blood flow changes, it is not a direct measure of neural activity in particular areas, and so it is not truly quantitative measure of mental activity in these brain areas
- Has poor temporal resolution as there is around a 4 second time lag behind the image on screen and the initial firing of the neuronal activity
- Critics argue that fMRI overlooks the networked nature of brain activity as it focuses only on localised activity in the brain - they claim that it is communication among the different regions of the brain that is most critical to mental function
11
Q
Evaluation of EEG’s - Strengths
A
- EEG’s have proven invaluable in clinical diagnoses - e.g. epileptic seizures are caused by disturbed brain activity which means that normal EEG readings suddenly change and similarly, it has contributed to our understanding of the stages of sleep, being a more useful method of diagnose conditions allowing people to access treatment
- Have a high temporal resolution which can accurately detect brain activity at a resolution of a single millisecond (even less in some cases) and this means the researcher can accurately measure a particular task or activity with the brain activity associated with it
- They are much cheaper than fMRI’s and so it is possible to use larger sample sizes and therefore results are more likely to be externally valid and EEG’s can be used more widely in research
12
Q
Evaluation of EEG’s - Weaknesses
A
- The main drawback is their poor spatial resolution as the EEG signal is not useful for pinpointing the exact source of neuronal activity because electrical activity can be picked up by several neighbouring electrodes; as a result, researchers are unable to distinguish between activities originating in different adjacent locations of the brain
- EEG’s can only detect the activity in superficial regions of the brain, for example this means that it cannot reveal what is going on in the deeper regions of the brain such as the hypothalamus or hippocampus - electrodes can be implanted in non-human animals to achieve this, but it is not ethically permissible to do this with humans as it would be too invasive
13
Q
Evaluation of PME - Strengths
A
- Allow for more detailed examinations of the neurochemical and anatomical aspects of the brain that would not be possible with the sole use of non-invasive techniques e.g. researchers can examine deeper regions of the brain such as the hippocampus
- Has contributed massively to our understanding of key processes of the brain e.g. structural abnormalities of the brain have a correlation with changes to neurotransmission in those who have schizophrenia and both Broca and Wernicke relied on PME to establish links between language and the brain
- Allow us to improve medical knowledge and generate hypotheses for further study
14
Q
Evaluation of PME - Weaknesses
A
- PME can only show physiology, whereas technique such as fMRI can capture dynamic brain activity
- Can lack validity due to small sample sizes
- Because people die in a variety of circumstances and at varying stages of disease, these factors can influence the postmortem brain, and the length of time between death and examination, drug treatment and age of death are also possible influences - this makes it hard to have cases and controls, and so causation is an issue within PME
- The approach is limited because it is retrospective as the person is already dead and because of this, the researcher cannot follow up on anything that arises concerning a possible relationship between brain abnormality and cognitive functioning
- Patients may not be able to provide informed consent before death - unethical
15
Q
Evaluation of ERP’s - Strengths
A
- High temporal resolution
- Enable determination of how processing is affected by experimental manipulation making it more robust as a method as it can eliminate extraneous activity
- Non-invasive
