L10 - Ways Of Studying The Brain

Question 1

4 ways of studying the brain

Answer 1

FMRI
EEG
ERP
Post mortems

Question 2

What does FMRI stand for

Answer 2

Functional magnetic resonance imaging

Question 3

What does EEG stand for

Answer 3

Electroencephalogram

Question 4

What does ERP stand for

Answer 4

Event related potential

Question 5

FMRI

Answer 5

• The principle behind it is that neurons most active during a given task will be using more energy & needs glucose and oxygen carried in the bloodstream so the blood flow to active areas of the brain should increase over control levels.
• fMRI scans indirectly measures blood flow through the concentration of oxygen in the blood stream
• Therefore the signal used in fMRI is called the BOLD contrast (Blood Oxygen Level Dependent)
  E.g. a participant might be asked to alternate between periods of doing tasks (e.g. looking at a stimulus for 30 seconds, then closing their eyes for 30 seconds – the fMRI can then be used to identify which parts of the brain are active during each task.

Question 6

FMRI application

Answer 6

• One innovative and recently emerging application of fMRI has been in lie detection. Supporters of fMRI prefer this method (i.e. checking the blood flow in the brain) as opposed to the normal lie detection method such as pulse reading, skin temperature and respiration. Supporters argue it is hard to fake blood flow!
• fMRI scans are important in understanding more about brain localisation

Question 7

Evaluation of FMRI

Answer 7

strengths
- non-invasive
- spatial resolution
weaknesses
- temporal resolution
- causation
- individual neurons

Question 8

Non-invasive

Answer 8

• Unlike scanning techniques like PET, fMRI’s do not rely on the use of radiation.
• fMRIs are non-invasive- the participant is required only to remain still and quiet in the scanner. It 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 localisation of function.

Question 9

Spatial resolution (FMRI)

Answer 9

• 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.

Question 10

Causation (FMRI)

Answer 10

• 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.
• In addition, some psychologists argue that fMRI scans can only show localisation of function within a particular area of the brain, but are limited in showing the communication that takes place among the different areas of the brain, which might be critical to neural functioning.

Question 11

Temporal resolution (FMRI)

Answer 11

• fMRI scans have poor temporal resolution.
• Temporal resolution refers to the accuracy of the scanner in relation of 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.

Question 12

Individual neurons (FMRI)

Answer 12

• fMRI’s only provides information on what brain area is active during different cognitive tasks- it cannot home in on the activity of individual neurones. It therefore does not provide a complete picture of brain activity which means that it is limited in the amount of information it provides.

Question 13

EEG

Answer 13

• The EEG provides an overall view of brain electrical activity and was developed by Hans Berger in 1929.
• A large number of small recording electrodes (24/32) are distributed over the surface of the skull which picks up the electrical activity of many millions of neurons. The EEG has some basic properties that can be used to characterise particular brain states through:
  • Amplitude: the size or intensity of the electrical activity
  • Frequency: the speed or rapidity of the electrical activity
  Also, there are two distinctive states of the EEG:
  • Synchronised pattern: this is where a recognizable waveform can be identified in the EEG recording
  • Desynchronised pattern: this is where there is no recognizable waveform

Question 14

EEG application

Answer 14

EEG data can be used to detect various types of brain disorder (such as epilepsy) or to diagnose other disorders that influence brain disease (such as Alzheimer’s). For example, EEG readings of patients with epilepsy show spikes of electrical activity. EEG patterns in patients with brain disease and brain injury show overall slowing of electrical activity.

The EEG is also particularly useful for identifying the general state of the brain. It has been used extensively to study sleep and the different stages of sleep.

Question 15

EEG wave types

Answer 15

• alpha - awake, normal alert consciousness
• beta - relaxed, calm, meditation, creative visualisation
• theta - deep relaxation & meditation, problem solving
• delta - deep, dreamless sleep

Question 16

Evaluation of EEG

Answer 16

strengths
- temporal resolution
- diagnosis
weaknesses
- superficial
- spatial resolution

Question 17

Temporal resolution (EEG)

Answer 17

EEG’s provide recording of the brain’s activity in real time rather than a still image – this means that a researcher can accurately measure a particular task or activity for example, when an individual is doing a particular cognitive task such as a memory test, the reader can measure the brain activity as the test is happening. EEG’s therefore have good temporal resolution.

Question 18

Diagnosis

Answer 18

EEGs have helped to provide invaluable diagnosis of conditions such as epilepsy. It has also contributed to our understanding of the stages involved in sleep especially ultradian rhythms.

Question 19

Superficial

Answer 19

Because EEG’s can only detect the activity in superficial regions of the brain, it cannot reveal what is going on in the deeper regions such as the hypothalamus or hippocampus. For example, the hippocampus is really important in helping us to maintain our long term memories – this means that it is hard to understand the functioning of LTM’s through EEGs (although this can be done in animals by planting electrodes in their brains but perhaps not ethically viable)

Question 20

Spatial resolution

Answer 20

The EEG signal is not useful for pinpointing the exact source of neural activity, and it does not allow researchers to distinguish between activities originating in different but adjacent locations. EEGs therefore have poor spatial resolution.

Question 21

ERP

Answer 21

• ERP’s are very small voltage changes in the brain that are triggered by specific events or stimuli, such as cognitive processing of a specific stimuli.
• This procedure uses a similar array of recording electrodes as the EEG.
• But a stimulus (for example a sound or picture) is presented to the participant, and the psychologist looks for specific electrical responses to that stimulus.
• This may be difficult because it may be difficult to separate that particular electrical activity related to the task and the overall activity of the brain.
• This means that the stimulus has to be presented many times. The regular specific electrical responses to the stimulus gradually add together while the background electrical noise cancels itself out. In this way the event-related potential emerges

Question 22

ERP

Answer 22

• ERP’s are very small voltage changes in the brain that are triggered by specific events or stimuli, such as cognitive processing of a specific stimuli.
• This procedure uses a similar array of recording electrodes as the EEG.
• But a stimulus (for example a sound or picture) is presented to the participant, and the psychologist looks for specific electrical responses to that stimulus.
• This may be difficult because it may be difficult to separate that particular electrical activity related to the task and the overall activity of the brain.
• This means that the stimulus has to be presented many times. The regular specific electrical responses to the stimulus gradually add together while the background electrical noise cancels itself out. In this way the event-related potential emerges

Question 23

How do ERP’s work?

Answer 23

1. Electrodes are placed on the persons head,
2. a person is presented with a sequence of stimuli and a recording of the brains electrical impulses is performed during the presentation
3. The person is presented with one familiar (the person’s own name) stimuli and four unfamiliar names
4. For example, the stimuli could be the person’s name (familiar stimuli) and irrelevant to the persons surname (unfamiliar stimuli)
5. Each of the names are repeated 30 times and they are also presented in an auditory form through a headset where each name is presented randomly
6. So, a person hears each of the five names 30 times and the reaction is recorded each time (total – 150 times)
7. This is the amount of ERP trials
8. The ERPs summate the brain reactions to each stimuli and therefore has 30 brain impulses for each stimuli
9. The average reaction will be statistically and different between the familiar and unfamiliar names
10. ERP to test if all information presented is recognised by the person is extremely accurate by comparing the average brain waves for unfamiliar and familiar stimuli

Question 24

Evaluation of ERP’s

Answer 24

strengths
- temporal resolution
- absence of behavioural response
weaknesses
- spatial resolution
- lack of standardisation

Question 25

Temporal resolution (ERP)

Answer 25

• The interval between stimulus presentation and the beginning of the ERP is known as the latency of the response.
• A unique feature of the ERPs is their very short latency, which is measured in milliseconds- thousands of a second (in contrast the latency for fMRIs is measured in seconds).
• This means that ERPs can reflect the very early stages of cognitive processing – such as face processing and working memory

Question 26

Lack of behavioural response

Answer 26

An ERP can measure the processing of stimuli even in the absence of a behavioural response. ERP recordings make it possible to monitor covertly the processing of a particular stimulus without requiring the person to respond to them. This means that the information gathered is true and not affected by

Question 27

Spatial resolution (ERP)

Answer 27

ERPs like EEG’s have a poor spatial resolution. With recording electrodes spread all over the scalp it is possible to localise components of the ERP to general areas of the cortex. However is it not possible to localise ERPs components to specific areas of the cortex. This means that we cannot be sure about what brain areas are active or responsible for specific behaviours.

Question 28

Spatial resolution (ERP)

Answer 28

ERPs like EEG’s have a poor spatial resolution. With recording electrodes spread all over the scalp it is possible to localise components of the ERP to general areas of the cortex. However is it not possible to localise ERPs components to specific areas of the cortex. This means that we cannot be sure about what brain areas are active or responsible for specific behaviours.

Question 29

Lack of standardisation

Answer 29

There is a lack of standardisation in ERP methodology between different research studies so findings can’t be confirmed which further questions whether findings can be generalised about ERPs. Furthermore, in order to get the correct data in ERP studies, extraneous variables (such as background noise) must be minimised and this is not always possible in reality

Question 30

Post-mortems

Answer 30

• a researcher may study a person while they are alive that suggests possible underlying brain damage.
• So, when a person dies, the researchers can compare his/her brain to look for abnormalities that might explain that behaviour and compare this to controls who do not show that abnormal behaviour.
  E.g. 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. This later became known as Broca’s area. Similarly, Wernicke discovered a region in the left temporal lobe, which is important for language comprehension and processing, which is now known as Wernicke’s area.
• Iverson examined the brains of deceased schizophrenic patients and found that they all had a higher concentration of dopamine, especially in the limbic system, compared with brains of people without schizophrenia, highlighting the importance of such investigations.

Question 31

What else do post-mortems allow for?

Answer 31

• Furthermore, post-mortem studies allow for a more detailed examination of anatomical and neurochemical aspects of the brain than would be possible with other techniques.
• They also enable researchers to examine deeper regions of the brain such as the hypothalamus and hippocampus, something that is not as easy with other methods of investigation.
• Nowadays it is possible to carry out brain scans on deceased individuals which means that the coroner does not have to actually cut the brain.

Question 32

Evaluation of post-mortems

Answer 32

strengths
- more detailed
- understanding mental illnesses
weaknesses
- individual differences
- ethical issues
- retrospective

Question 33

More detailed (post mortems)

Answer 33

A Strength of Post mortem studies is that they allow for a more detailed examination of anatomical and neurochemical aspects that would not be possible through fMRI’s and EEG’s. It enables researchers to examine deeper regions of the brain such as the hypothalamus and hippocampus. For example, it was possible to look at HM’s brain after he died and see the effects of his hippocampus being removed

Question 34

Understanding mental illnesses

Answer 34

Harrison (2000) claims that post-mortem studies have played a central part in our understandings of the origins of schizophrenia and other mental illnesses. 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

Question 35

Ethical issues

Answer 35

While post-mortem examinations are ‘invasive’, this is not an issue because the patient is dead. 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.

Question 36

Individual differences

Answer 36

There are too many individual differences in how people die – being at different stages of disease and circumstances. The length of time between death and post-mortem (post-mortem delay), drug treatments and age at death are all confounding variables which can affect the outcome of the post mortem. This means we cannot make generalisations about brain functioning due to these individual differences

Question 37

Retrospective

Answer 37

Carrying out post-mortem research is limited as it is retrospective because the person is already dead – so follow-ups cannot be made (although if scans were completed when the deceased was alive – structural comparisons can be made between the brain as it was alive and as it is now dead).