6. ways of studying the brain

ways to study the brain

1. functional magnetic resonance imaging (fMRI)

2. electroencephalogram (EEG)

3. event related potentials (ERP)

4. post mortem examinations

functional magnetic resonance imaging

• used to measure brain activity while a person is performing a task

• it detects radio waves from changing magnetic fields

• enables researchers to detect which regions of the brain are rich in oxygen and thus are active (known as the haemodynamic response)

• produces 3 dimensional images known as activation maps

spatial resolution

• has high spatial resolution

• provides clear images by the millimetre - allows for safe, detailed localisation of brain activity

• makes it useful for mapping active brain areas during tasks helping researchers and clinicians understand which parts of the brain are involved in specific cognitive functions

non invasive

• protected from injections of potentially harmful substances

• ie PET scans involve injection of a radioactive tracer

• means has good ethical validity

temporal resolution

• poor temporal resolution

• there is a 5s time lag between activity and image appearance limiting ability to detect real time brain activity - may miss moment to moment changes

• may not be ideal for studying fast cognitive processes like decision making or quick emotional responsesn

expensive

• due to highly technical, specialist equipment and highly skilled personnel involved

• use is limited to countries, regions or institutions that can afford to purchase and maintain the scanners

• economic considerations also means sample sizes tend to be small which limited external validity and reliability of the data

electroencephalogram

• measures electrical activity within the brain via electrodes that are fixed to an individuals scalp using a skull cap and conductive gel

• the scan recording presents the brainwave patterns that are generated from the action of thousands of neurons, providing an overall account of brain activity

• amplitude shows intensity, and frequency the speed of activation

EEG uses

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

temporal resolution

• excellent temporal resolution

• it detects brain activity changes in under a milisecond making it ideal for measuring real time neural activity, especially in conditions like epilepsy or during sleep studies

• makes it useful in both clinical diagnoses and research on brain states eg REM sleep

spatial resolution

• poor spatial resolution and generalised data

• cannot pinpoint the source of neural activity or distinguish between close brain areas - only detects surface activity within accessible regions, so cannot provide insight to what is happening in deeper regions ie the amygdala

• less useful for localising function compared to fMRI

unrepresentative findings

attaching electrodes to the scalp is beset with problems

• may be placed innacurately, or move

• each persons head shape and size is unique

• some may not work during procedure or need replacing

all lead to unrepresentative findings

event related potentials

• same apparatus and technique as EEG

• record when there is activity in response to a stimulus

• they are tiny voltages generated in brain structures and can be stimulated via a wide variety of sensory, cognitive or motor events

• recording undergoes statistical averaging - the EEGs waveform peaks and dips show exactly when a specific cognitive process happens in the brain in relation to when the stimulus is presented

temporal resolution

• high temporal resolution and specificity in measuring cognitive processes

• its derived from EEG data but is more targeted so it can track precise neural responses to stimuli, offering insights into mental processes like attention allocation

• makes it widely used in cognitive neuroscience for studying stimulus-response patterns and deficits

cheaper

• cheaper than fMRI

• more likely to be used more readily and widely than other more expensive techniques

background noise

• difficult to eliminate background noise and lacks standardisation

• requires clean data with minimal interference, but this is often hard to achieve meaning variability makes comparisons between studies difficult

• affects the reliability and validity of ERP findings across different research settings

electrode cap

• participants may find wearing it uncomfortable

• could lead to subject attrition so lower sample sizes and less robust data

• participants may wriggle, scratch or pull at it altering validity

post mortem examinations

• when the brain is analysed after death to determine whether certain observed behaviours during the persons lifetime can be linked to structural abnormalities in the brain

• may also involve comparison with a neurotypical brain in order to ascertain the extent of the difference

strength

• vital for early understanding of brain-behaviour relationships

• broca, wernicke and HMs case studies helped identify language and memory areas as damage to specific brain areas were linked to behaviour deficits (speech or memory loss) forming foundational knowledge

• still contributes today especially when used alongside modern neuroimaging for confirmation

causation and consent

• issues with causation and consent

• damage seen post mortem may not explain behaviour (eg due to decay or unrelated trauma) - eg HM could not consent due to memory loss

• raises ethical concerns over studying brains without fully informed consent, undermining the reliability and ethical acceptability of post mortem findings in some cases