Brain scans Flashcards
fMRI
Works by identifying changes in the levels of oxygen in blood
When brain area is more active leads to more oxygen
Produces a 3D image called activation map
Used to identify which specific parts of the brain are active
fMRI
Much safer because its non invasive and doesn’t use radiation
Unlike PET uses small amount of radiation . Despite being low levels could still lead to potential harm
Thus fMRI is more appropriate technique as a way of studying the brain
fMRI strength and limitation
Have higher spatial resolution than EEG
Which is important feature of the brain scans because it can accurately identify specific areas of the brain involved in behaviour,
depicting behaviour by the millimetere providing a clear image of how the brain is localised
However has poor temporal resolution as there is a 5 second time lag behind images on screen and initial firing of nueronal activity
Thus fMRI may not really represent moment to moment brain activity
EEG
electrodes placed on scalp
electrical signals are graphed to see persons general brain activity
Used to detect sleep patterns such as sleep , arousal or to diagnose conditions such as brain tumours and epilepsy
EEG
High in temporal resolution, enables to take real time recording
Rather than still image of brain as the case of fMRI
Gain accurate measure of brain activity increasing its validity as a way of studying the brain
EEG limitation
Low spatial resolution
Can only provide information on general brain activity
Cannot pinpoint exact source of nueral activity
Unlike ERP which enables researcher to identify specific brain activity
Finding may be less valuable understanding In developing our understanding
Post mortems
Brain of dead patient is examined and dissected to see physical/ structural abnormalities
Compared with a brain that does not show this behaviours or mental process
Used in person who had rare disorder or defect
Used in the identification of brocas area
Post mortems strength
Only non invasive way which means it’s possible to get a more detailed examination
E.g meant that researchers have been able to study deeper areas of the brain
Such as hypothalamus
Increasing validity of post mortems as a way of studying the brain
Post mortems limitation
Hard to establish cause and effect with post mortems study
As there are many extraneous variables that cannot easily be controlled such as age at time of death or whether they received a drug treatment for a disorder
More challenging to interpret role of specific areas of brain in behaviour
Limits internal validity of the findings of these studies and thus using post mortems to study the brain
Event related potential ERPs
Electrodes are placed on the scale
ERP shows brain response to specific stimulas
Stimulus is presented to induvidual many times
All extraneous brain activity from original EEG is filtered out leaving only those responses that are linked to the presentation of the stimulus
What do ERPs look like?
Are graphed, base line measure line is shown with a test line to the difference in brain activity
When are ERPs used ?
Study a range of cognitive processes such as attention memory or perception in response to specific stimuli
ERPs strength
High temporal resolution, identify brain activity every millisecond so researchers can see brain activity in real time
However poor spatial resolution as they can only detect brain activity in general brain areas rather than specific location of brain activity
ERPs limitation
Hard to obtain meaningful data as they can be affected by external factors such as background noise so could take many trials as it’s hard to control these factors
Limits validity of ERPs as a means of studying the brain for a range of brain processes
