Ways of studying the brain Flashcards
fMRI
Functional magnetic resonance imaging
-A brain scanner which measures increased blood flow to brain sites when individuals are asked to perform cognitive/physical tasks.
-Increased blood flow indicates increased demand for oxygen in that area
-Produces 3D images showing which parts of the brain are involved in a particular mental process, important for our understanding of localisation of function
-Can help build up a map of localisation. Can identify brain sites which received increased oxygen when a ppt is asked to solve maths problems
Strengths of fMRI
-Non-invasive
No insertion of instruments unlike PET and no exposure to radiation
Beneficial to the economy as there is no recovery time so people don’t have to be off work
Weaknesses of fMRI
-Only measures blood flow- can’t see the activity of individual neurons therefore its hard to tell what brain activity is being represented. Findings may be misinterpreted
-fMRI may overlook the interconnectivity of brain sites. Fails to account for the importance of brain sites connecting with each other
-Expensive
EEG is cheaper
Can only capture a clear imagine if the person stays still- may not be worthwhile for the NHS to fund it
EEGs
Electroencephalogram
Measures electrical activity in the brain using electrodes attached to the scalp and measures how electrical activity in the brain varies over time
They can detect epilepsy and Alzheimer’s
Strengths of EEG’s
-Records brain activity over time and can, therefore monitor changes as a person switches from task to task or one state to another
-Have medical applications is diagnosing disorders
-Non-invasive- No insertion of instruments unlike PET and no exposure to radiation. Basically risk free
-Cheaper than fMRI thus making them more available
Weaknesses of EEG’s
-Only monitor electrical activity in outer layers of the brain, therefore cannot reveal electrical activity in deeper brain sites
-Not highly accurate- hard to pinpoint exactly which area is producing this activity therefore cannot distinguish differences in activity between 2 closely adjacent areas
-Uncomfortable, could result in an unrepresentative reading as the patient’s discomfort could trigger cognitive responses to the real time situation
ERP’s
Event-related potentials
Very small voltage changes in the brain triggered by specific events or stimuli which are measured using an EEG
Measures small voltages of electrical activity when a stimulus is presented. The stimulus needs to be repeatedly presented as its difficult to pick out from other electrical signals in the brain
ERP’s Strengths
-Provides a continuous measure of neural activity in response to a stimulus. Can be directly recorded
-Derived from EEG- excellent temporal resolution compared to fMRI. Led to their widespread use in the measurement of cognitive functions and deficits
-Non-invasive
ERP’s Weaknesses
-Only monitors the outer layers of the brain
-Extraneous stimuli must be eliminated in order to collect pure data
-Lack of standardisation in methodology between studies. Hard to replicate experiments and confirm findings in a peer review study
Post-mortem examinations
-Brains from dead individuals who displayed cognitive abnormalities whilst alive can be dissected to check for structural abnormalities.
Post-mortem Strengths
-Allow for detailed examinations and measurement of deep brain structures not measurable by brain scans
-Brain tissue can be examined in detail, deep structures of the brain can be investigated after death
-Highly applicable. Broca and Wernicke both relied on post mortem studies in establishing links between language, brain and behaviour decades before neuroimaging ever became a possibility
Post-mortem Weaknesses
The issue of causation- The deficit a patient displays during their lifetime may not be linked to the deficits found in the brain, may be a result of another illness
Ethical Issues- Deceased people are not able to provide informed consent such as HM because of his lack of short term abilities. There will be problems with replicability because future ethical guidelines will be stricter
