Ways of Investigating the Brain Flashcards
Define fMRI.
A method used to measure brain activity while a person is performing a task. It detects changes in blood oxygenation and flow that occurs due to neural activist in specific brain areas.
Outline how fMRI works.
When a brain area is more active, it consumes more oxygen, and blood flow is directed to the active area. Thus, the fMRI produces a 3D image showing which parts of the brain are involved in particular processes.
Define EEG.
A record of the tiny electrical impulses produced by the brain’s activity. Measured via electrodes using a skull cap
Define post mortem examination.
The analysis of a person’s brain following their death to establish the underlying neurobiology of a particular behaviour.
What is the difference between an EEG and ERP?
An EEG measures electrical activity within the brain. Whereas ERPs are what us left when all extraneous activity from an EEG recording is filtered out.
What does fMRI produce?
fMRI produces a 3D image showing which parts of the brain are active, and therefore must be involved in particular mental processes.
What are EEGs used for?
EEG is often a diagnostic tool. Eg unusual arrhythmic patterns of brain activity may indicate abnormalities eg epilepsy.
Evaluation of fMRI?
+ Unlike other scanning techniques eg PET scans, fMRI doesn’t rely on the use of radiation, and is safe.
Also produces images with a high spatial resolution, showing detail by the millimetre -> menacing fMRI can provide a clear picture of how brain activity is localised.
Also non-invasive.
- fMRI is expensive compared with other techniques and can only capture a clear image is the person stays still.
Also, has a poor temporal resolution because of the 5 second lag between initial neural activity and image.
This means it may not truly represent moment to moment activity.
Evaluation of EEG.
+ v high temporal resolution. EEGs can detect brain activity at a resolution of one millisecond.
- EEG produces a generalised signal from 1000s of neurones.
Also difficult to know the exact source of neural activity.
EEGs can’t distinguish the activity of different but adjacent neurons.
Evaluation of ERP?
+ ERPs have v good temporal validity, esp compared to fMRI.
Also ERPs are more specific than what can be achieved with raw EEG data.
- lack of standardisation in methodology between studies. Making it difficult to confirm findings in studies involving ERPs.
Also, background noise and extraneous material must be completely eliminated.
This may not always be easy to achieve.
Evaluation of post mortem?
+ Broca and Wernicke relied on post mortem studies.
They also improve medical knowledge.
They help generate hypotheses for further study.
- Observed damage in the brain may not be linked to the deficits under review, but to some other trauma (causation = issue).
Also, raises ethical issues of consent from the patient before death.
-> Patients may not be able to give informed consent.
