Ways of studying the brain Flashcards
(14 cards)
ways of studying the brain
- Functional magnetic resonance imaging (fMRI)
- Electroencephalogram (EEG)
- Event-Related Potentials (ERPs)
- Post-mortem Examinations
fMRI
fMRI works by detecting the changes in blood oxygenation flow that occur as a result of neural (brain) activity in specific parts of the brain
when a brain area is more active it consumes more oxygen and to meet this increased demand, blood flow is directed to the active area (haemodynamic response)
produces 3D images (activation maps) showing which part of the brain are involved in particular mental processes, this has important implications for our understanding of localisation of function
shows activity about one second after it occurs
good spatial resolution: accurate to within 1-2mm in the brain
5 second time lag between image and brain activity
fMRI evaluation
- STRENGTHS
P: can detect activity in deeper regions of the brain
E: show areas such as hippocampus subcortical
L: lead to a valid understanding of the function of the brain
P: record specific brain activity which can pinpoint specific responses and the exact source of brain activity
E: show activity about one second after it occurs which allows people to understand exactly where the issue is located and how it is affecting the patient
L: practical applications: useful for providing treatment and establishing cause and effect
P: non invasive and safe, unlike eg. PET scans which use radiation
P: high spatial resolution (accurate within 1-2mm)
fMRI evaluation
- LIMITATIONS
P: fMRI machines are expensive to buy/maintain and require trained operators
E: research is expensive and difficult to organise
E: use of fMRI machines are limited and often other machines are used before to prevent the NHS paying millions to operate each time
L: negative impact on the economy
P: by pinpointing exact source of brain activity, it ignored communication between areas & networked structure of the brain
E: ignores plasticity and functional recovery
L: limited/ ignore complexity of brain function
P: low temporal resolution
E: cannot provide a ‘real time’ recording of brain activity as there is a 5 second lag between image and brain activity, one image taken every few seconds
E: not an accurate representation of timing
L: lacks internal validity, many brain processes are too fast to study
P: ppt has to be still, experiments with body movement are not possible, limited
EEG
EEGs measure electrical activity within the brain via electrodes that are fixed to an individuals scalp using a skull cap
the scan recording represents the brainwave patterns that are generated from the action of millions of neurons, providing an overall account of brain activity
there can be anything from 2-3 to over 100 electrodes
electrodes measure the activity of cells immediately under the electrode, so using more electrodes give a fuller picture
‘real time’ recording of brain activity (within a millisecond)
eg. measuring brain waves in sleep cycle
ERPs (event related potentials)
statistical averaging technique
one issue with EEG is that it may simply be an overly general measure of brain activity
however, with EEG data contains all the neural responses asscociated with specific sensory, cognitive, motor events.
these specific responses can be teased out and isolated.
using a statistical averaging technique, extraneous brain activity from the original EEG recording can be filtered out leaving only event-related potentials
ERPs are types of brain waves that relate to a specific function (eg. presentation of a specific stimulus or performance of a specific task)
research has revealed many different forms of ERP and how, for example, these are linked to cognitive processes such as attention and perception
‘real time’ recording of brain activity (within a millisecond)
EEG/ERP evaluation
- STRENGTHS
P) cheaper, more practical methods than scanning
E) more likely to be chosen as they are more widely available
E) eg compared to fMRI machines
L) positive implication for the economy as they can be used more while costing the NHS less, allow wide-scale research
P) high temporal resolution
E) provides a ‘real time’ recording of brain activity within milliseconds
E) EEGs and ERPs are highly accurate when studying the timing of brain activity, whereas FMRIs have a lag
L) higher internal validity
P) non invasive, non surgical, safe unlike eg. PET scans which use radiation
P) ERP allows researchers to isolate and study how individual cognitive processes take place in the brain, eg. in response to a stimulus by removing background electrical noise
P) practical applications
E) historically important in understanding brain activity
E) eg. medical diagnosis of epilepsy, experimental demonstrate stages of sleep
L) useful for both understanding of brain function, and diagnosis/treatment of dysfunction
EEG/ERP evaluation
- LIMITATIONS
P) poor spatial activity: only reasonably accurate for activity measured close to the electrode
E) finer detail is missed, eg deeper brain regions so this type is only suitable for certain research questions
E) very general and holistic account of brain activity rather than a detailed 3D image (fMRI)
L) limited, lacks an idiographic method
P) lack of standardisation in ERP methodology between different studies
E) between different studies there is inconsistency, so it is difficult to confirm any findings
L) lack of reliability across different institutions, low external validity
Post-mortem examinations
technique involving the analysis of a persons brain following their death
in psychological research, individuals whose brains are subject to a post-mortem 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 within the brain are examined after death as a means of establishing the likely cause of the affliction the person suffered
may also involve comparison with a neurotypical brain in order to ascertain the extent of the difference
eg discovered Broca’s area for speech production by Tan
Post-mortem examinations: evaluation
- STRENGTHS
P) provided a foundation of early understanding of key processes in the brain
E) Broca and Wernicke relied on post mortem studies to establish language centres
E) eg Tan, Broca’s area, speech production
L) improved medical knowledge and have helped to generate hypotheses for further study
P) no discomfort experienced by the individual as they are not alive
E) in comparison to fMRIs which can be claustrophobic, noisy, and stressful
L) reduces ethical issues
P) high spatial resolution
E) allows the study of microscopic brain structures down to neuronal level
L) accurate/ internally valid
Post-mortem examinations: evaluation
- LIMITATIONS
P) conducted on a dead person so no brain activity measured
E) researcher cannot pinpoint brain activity being specific to function or brain plasticity
L) limited
P) issues with comparison of functioning prior to death
E) little info about how the person managed before they died
E) neurotypical brain comparison may cause issues with generalisation to the wider public and understanding of brain function
L) low external validity
P) some brains may have been affected by the reason for the death
E) accuracy of measuring brain function/damage can be questioned as can’t establish cause and effect
E) eg has disease caused brain damage or has damaged caused disease
L) unusual behaviour in life and damage found is correlational; low internal validity
extra evaluation
some researchers have conducted studies combining the techniques of EEG and fMRI
can compare results of tasks performed with both, while taking advantage of the high temporal resolution of EEG and high spatial resolution of fMRI
+ scientific methods
+ practical applications
-rare individuals -> low population validity, idiographic
-biological reductionism
what is meant by spatial resolution
level of accuracy in identifying the exact location of a brain structure or brain activity in space
where activity happened
what is meant by temporal resolution
level of accuracy in identifying the exact location of brain activity in time
when activity happened
