Ways of Studying the Brain (AQA A Level Psychology)

Functional Magnetic Resonance Imaging (fMRI) measures oxygenated blood flow in the brain i.e. brain activity 

Oxygenated blood has a different resonance than deoxygenated blood

• More active areas of the brain receive more oxygenated blood

fMRI uses large magnets to detect oxygenated haemoglobin blood flow

• The blood flow reacts to the scanner's magnets

• Deoxygenated blood is present in less active/non-active regions of the brain

• The blood flow equates to activity in the brain which in turn indicates which specific structures are working hard at that point in time

A computer transforms the information into a brightly coloured 3D image which is mapped using voxels (each voxel = thousands of neurons)

The active areas of the brain can then be compared with areas that are lower in activity which is indicated on the fMRI scan image via the degree of bright colour

fMRI scans have good spatial resolution of 1mm

• This is a strength as it enables researchers to precisely identify the active brain regions and patterns of activation over time

• This in turn can lead to increased insight into how the brain works e.g. the role of dopamine in addiction

It is a non-invasive procedure which means that participants are protected from injections of potentially harmful substances (PET scans involve injection of a radioactive tracer into the participant)

• This means that fMRI has good ethical validity

fMRI is slow, having a 5-second delay between brain activity and measurement

• This is a limitation as could mean that some important information is not detected due to the delay

  • Therefore fMRI scans cannot 'prove' a theory, they can only indicate biological correlates to behaviour (e.g. lack of pre-frontal cortex activity and low impulse control)

fMRI scans are expensive due to the highly technical, specialist equipment and highly skilled personnel involved

• This means that its use is limited to countries, regions or institutions that can afford to purchase and maintain the scanners in the first place

• Economic considerations also mean that sample sizes in fMRI research tend to be small, which limits both the external validity and reliability of data

The use of an electroencephalogram (EEG) involves the placing of electrodes on the scalp which record brain activity

Usually between 22-34 electrodes are used but there can be any number from 2-100 depending on the age and size of the participant and what the aim of the research is

The electrodes are fitted to a cap that is placed on the participant's scalp along with a conductive gel

The electrodes measure the activity of the cells directly below them

• The more electrodes there are, the more detailed information and a comprehensive picture of the brain can be derived

Brain activity is shown via brain waves

• This presents visually as a series of lines which have distinct patterns 

The amplitude shows the brain intensity and the frequency shows the speed of activation 

• this indicates the nature of the brain activity (e.g. if the brain is in 'resting' mode, if it is highly active etc.)

• EEGs may be used to investigate sleep disorders, seizures, memory problems

EEG been historically important in understanding sleep patterns e.g.

• Dement & Kleitman (1957) used EEG to determine the five different stages of sleep

  • A key finding was that eye movements were linked to phases of dreaming (this was termed REM = rapid eye movement)

  • Eye movements reflected the type of dream e.g. a dream about throwing tomatoes at a wall occurred when the participant's eyes moved side to side

  • These findings were only possible due to the use of EEG

The use of EEG in the study described above contributes to the overall reliability of the technique

• The researchers used a systematic timetable for waking participants and collecting dream reports

• This standardised procedure and use of an objective measure such as EEG makes the study replicable

  • Replicability is a strength as it means that consistency of results over time can be checked = reliability

EEG can only detect surface activity within accessible regions of the brain

• This is a limitation as EEGs cannot provide insight as to what is happening in deeper regions of the brain (e.g. the amygdala)

• Therefore EEG is limited as to what it can achieve in terms of measuring brain activity

Attaching electrodes to the scalp is beset with problems

• The electrodes may be placed inaccurately or may move during the procedure

• Each person's head shape and size is unique so the placement of the electrodes cannot be done on a 'one size fits all' basis

• Some of the electrodes may not work during the procedure or need replacing

  • All of the above can lead to unrepresentative findings

Event-related potentials (ERP) use the same apparatus and technique as EEG

ERPs record when there is activity in response to a stimulus 

ERPs are tiny voltages generated in brain structures in response to specific events or stimuli

ERPs can be stimulated via a wide variety of sensory, cognitive or motor events

An original EEG recording is used

• The 'white noise' of the recording is filtered out to leave only what the researcher is interested in investigating

  • This is done using a statistical averaging technique

  • The EEG's waveform peaks and dips show exactly when a specific cognitive process happens in the brain in relation to when the stimulus is presented e.g. language, attention

ERPs are much cheaper than the more costly fMRI scanning

• This is a strength as it means that they are likely to be utilised much more readily and widely than other more expensive techniques

• Therefore conditions such as epilepsy may be easier to diagnose

ERPs record the brain's activity in 'real-time'

• They take measurements of brain activity every millisecond

• This is extremely useful as it results in an accurate measurement of electrical activity when a participant performs a specific task

Participants may find wearing the electrode cap very uncomfortable

• This is a limitation as it could lead to subject attrition which would in turn mean a lower sample size and less robust data

• Additionally, if the cap is uncomfortable participants may wriggle, scratch or pull at the cap which could alter the validity of the findings

An ERP signal cannot pinpoint with 100% accuracy the exact source of specific brain activity

• More than one electrode may pick up the activity's signal

  • This can lead to confusion as to what the signal is and from which part of the brain it originates

Post-mortem examination (PME) of the brain involves examining the brain after death (usually when it has been cut into slices) to determine the cause of behaviour(s) or dysfunction experienced when the patient was alive

This technique was used in the early days of biological psychology as there was no sophisticated technology available to look at a living brain

PME is used to investigate the structure of the brain - it cannot detect brain activity

• The findings are used to infer a correlation with behaviour e.g.

  • why can patient X not recall any new information?

  • why is patient Y unable to speak in full sentences?

PME is used today if there are no alternatives available e.g.

• Alzheimer’s disease can only really be determined by conducting a PME

PME of the brain was used alongside other techniques to investigate the damage done to HM’s brain and helped to determine the link between the hippocampus and the formation of new memories

• A year after HM died, his preserved brain was sent to the University of California where it was sliced into 2,401 sections

  • These slices were then placed on slides and scanned, as a permanent neurological research resource

Paul Broca’s (1861) PME of his patient ‘Tan’ provided a scientific breakthrough in terms of locating the language area of the brain in the left hemisphere

PME may involve comparing the damaged brain to a non-damaged brain in order to assess which regions/structures are implicated in the behaviours observed when the patient was alive

PME enables researchers to study a brain without inflicting any harm on the living person

• As long as the participant has given consent for this to take place this is an ethical way in which to investigate brain structure/abnormality

PME can help clinicians to confirm a diagnosis e.g.

• the patient was suspected of having Alzheimer’s

• PET scans were conducted which indicated that Alzheimer's was present but the scan itself could not diagnose this with 100% confidence

• the PME determined conclusively that the patient suffered from Alzheimer's

It is difficult to compare post-mortem slices of a brain after death with actual brain functioning before death

• This means that PME lacks ecological validity as the 'real', living brain of the person when alive is not reflected in the use of this technique

It may not always be possible for researchers to obtain fully informed consent from a prospective PME participant

• This is particularly true if the person's ability to give consent is severely compromised by their disorder e.g. HM's extreme amnesia meant that consent by proxy only was possible

• This limits the ethics of PME to some extent