Biopsychology: Ways of studying the brain Flashcards
What are the 4 scanning techniques?
- fMRI
- EEG
- ERP
- Post mortem
What’s an fMRI scan?
Functional magnetic resonance imaging (fMRI) is a brain-scanning technique that measures blood flow in the brain when a person performs a task. fMRI works on the premise that neurons in the brain that are the most active (during a task) it consume more oxygen. so it can get this extra oxygen, and blood flow is directed to the active area (haemodynamic response). An fMRI creates a dynamic (moving) 3D map of the brain, highlighting which areas are involved in different neural activities.
What’s an EEG scan?
The electroencephalogram (EEG) is a neuroimaging test which can detect and record minute changes in electrical activity within the brain. This is recorded using microelectrodes (large, flat electrodes stuck to the skin or scalp).
It produces a chart (an encephalogram) which shows how ‘brain waves’ vary by frequency (number of waves per second) and amplitude (height) of electrical output from the brain changes over time.
What’s an ERP scan?
Event-Related Potentials (ERP) use similar equipment to EEG, with electrodes attached to the scalp. However, the key difference is that a stimulus is presented to a participant (for example a picture/sound) and the researcher looks for activity related to that stimulus. However, as ERPs are difficult to separate from all of the background EEG data, the stimulus is present many times (usually hundreds), and an average response is graphed. This procedure, which is called ‘averaging’, reduces any extraneous neural activity which makes the specific response to the stimulus stand out.
What’s a post-mortem scan?
A post-mortem examination is when researchers study the physical brain of a person who displayed a particular behaviour while they were alive that suggested possible brain damage. An example of this technique is the work of Broca, who examined the brain of a man who displayed speech problems when he was alive. It was subsequently discovered that he had a lesion in the area of the brain important for speech production that later became known as Broca’s area.
Evaluation of fMRI scan?
+ An advantage of fMRI is that is non-invasive. Unlike other scanning techniques, for example, Positron Emission Tomography (PET), fMRI does not use radiation or involve inserting instruments directly into the brain and is therefore virtually risk-free. Consequently, this should allow more patients/participants to undertake fMRI scans which could help psychologists to gather further data on the functioning human brain and therefore develop our understanding of the localisation of function.
+ fMRI scans have good spatial resolution. Spatial resolution refers to the smallest feature (or measurement) that a scanner can detect, and is an important feature of brain scanning techniques. Greater spatial resolution allows psychologists to discriminate between different brain regions with greater accuracy. fMRI scans have a spatial resolution of approximately 1-2 mm which is significantly greater than the other techniques (EEG, ERP, etc.) Consequently, psychologists can determine the activity of different brain regions with greater accuracy when using fMRI, in comparison to when using EEG and/or ERP.
- fMRI scans have a poor temporal resolution. Temporal resolution refers to the accuracy of the scanner in relation to time: or how quickly the scanner can detect changes in brain activity. fMRI scans have a temporal resolution of 1-4 seconds which is worse than other techniques (e.g. EEG/ERP which have a temporal resolution of 1-10 milliseconds). Consequently, psychologists are unable to predict with a high degree of accuracy the onset of brain activity.
- fMRI scans do not provide a direct measure of neural activity. fMRI scans simply measure changes in blood flow and therefore it is impossible to infer causation (at a neural level). While any change in blood flow may indicate activity within a certain brain area, psychologists are unable to conclude whether this brain region is associated with a particular function.
Evaluation of EEG scan?
+ An advantage of EEG and ERP is that both techniques are non-invasive. Unlike other scanning techniques, such as Positron Emission Tomography (PET), EEG and ERP do not use radiation or involve inserting instruments directly into the brain and are therefore virtually risk-free. Furthermore, EEG and ERP are much cheaper techniques in comparison with fMRI scanning and are therefore more readily available. Consequently, this should allow more patients/participants to undertake EEG/ERPs, which could help psychologists to gather further data on the functioning human brain and therefore develop our understanding of different psychological phenomena, such as sleeping, and different disorders like Alzheimer’s.
+ An advantage of the EEG/ERP technique is that it has good temporal resolution: it takes readings every millisecond, meaning it can record the brain’s activity in real-time as opposed to looking at a passive brain. This leads to an accurate measurement of electrical activity when undertaking a specific task.
- However, one disadvantage of EEG/ERP is that these techniques have a poor spatial resolution. Spatial resolution refers to the smallest feature (or measurement) that a scanner can detect, and is an important feature of brain scanning techniques. The greater spatial resolution allows psychologists to discriminate between different brain regions with greater accuracy. EEGs/ERPs only detect the activity in superficial regions of the brain. Consequently, EEGs and ERPs are unable to provide information on what is happening in the deeper regions of the brain (such as the hypothalamus), making this technique limited in comparison to the fMRI, which has a spatial resolution of 1-2mm.
- Another issue with EEG is that electrical activity is often detected in several regions of the brain simultaneously. Consequently, it can be difficult pinpoint the exact area/region of activity, making it difficult for researchers to draw accurate conclusions.
Evaluation of ERP scan?
+ An advantage of EEG and ERP is that both techniques are non-invasive. Unlike other scanning techniques, such as Positron Emission Tomography (PET), EEG and ERP do not use radiation or involve inserting instruments directly into the brain and are therefore virtually risk-free. Furthermore, EEG and ERP are much cheaper techniques in comparison with fMRI scanning and are therefore more readily available. Consequently, this should allow more patients/participants to undertake EEG/ERPs, which could help psychologists to gather further data on the functioning human brain and therefore develop our understanding of different psychological phenomena, such as sleeping, and different disorders like Alzheimer’s.
+ An advantage of the EEG/ERP technique is that it has good temporal resolution: it takes readings every millisecond, meaning it can record the brain’s activity in real-time as opposed to looking at a passive brain. This leads to an accurate measurement of electrical activity when undertaking a specific task.
- However, one disadvantage of EEG/ERP is that these techniques have a poor spatial resolution. Spatial resolution refers to the smallest feature (or measurement) that a scanner can detect, and is an important feature of brain scanning techniques. The greater spatial resolution allows psychologists to discriminate between different brain regions with greater accuracy. EEGs/ERPs only detect the activity in superficial regions of the brain. Consequently, EEGs and ERPs are unable to provide information on what is happening in the deeper regions of the brain (such as the hypothalamus), making this technique limited in comparison to the fMRI, which has a spatial resolution of 1-2mm.
+ However, ERPs enable the determination of how processing is affected by a specific experimental manipulation. This makes ERP use a more experimentally robust method as it can eliminate extraneous neutral activity, something that other scanning techniques (and EEG) may struggle to do.
Evaluation of Post mortem scan?
+ Researchers have found damage in certain areas of the brain and they have been able to attribute specific functions to those areas as a result. Broca’s and Wernicke’s areas are both great examples. They were discovered at a time when advanced techniques such as the EEG and an fMRI were not available.
+ One strength of post-mortem examinations is that they provide a detailed examination of the anatomical structure and neurochemical aspects of the brain that is not possible with other scanning techniques (e.g. EEG, ERP and fMRI). Post-mortem examinations can access areas like the hypothalamus and hippocampus, which other scanning techniques cannot, and therefore provide researchers with an insight into these deeper brain regions, which often provide a useful basis for further research. For example, Iverson found a higher concentration of dopamine in the limbic system of patients with schizophrenia which has prompted a whole area of research looking into the neural correlates of this disorder.
- However, there are ethical issues in relation to informed consent and whether or not a patient provides consent before his/her death. Furthermore, many post-mortem examinations are carried out on patients with severe psychological deficits (e.g. patient HM who suffered from severe amnesia) who would be unable to provide fully informed consent, and yet a post-mortem examination has been conducted on his brain. This raises severe ethical questions surrounding the nature of such investigations.
- Another issue is that there are many extraneous factors that can affect the results/conclusions of post-mortem examinations. For example, people die at different stages of their life and for a variety of different reasons. Furthermore, any medication a person may have been taking, their age, and the length of time between death and post-mortem examination, are all confounding factors that make the conclusions of such research questionable.
