BP - Ways of studying the brain Flashcards
what is a post-mortem scan
- Investigate the brain after death
- If a person has had an affliction in their lifetime, the brain can be acquired and investigated
- Any damage found allows us to link that part of the brain to a particular function
- can draw comparisons to neurotypical brains
what is an MRI scan
- MRI scans allow us to investigate the structure of the brain
- Strong magnetic waves are sent through the body
- This affects hydrogen atoms and they are forced into a different position
- In doing this, the body’s atoms send out radio waves of their own
- The scanner picks up these signals and the computer turns them into an image
what is an fMRI scan
- fMRI scans allow us to observe and measure brain function
- This means we can see the areas that are currently active, not only the structure
- Works by detecting blood oxygenation to each area of the brain. This is called the BOLD signal.
what is an EEG (electroencephalogram)
- Electrodes are placed on the surface of the skull
- They measure changes in electrical activity when a person performs a specified task
- They recorded activity from groups of neurons in the brain, but it is a crude measurement shown in waves
- The type of wave shown indicate the part of the brain performing the task
- Can be used to diagnose epilepsy and brain death
what is an ERP
- Participants undergo multiple EEGs and are presented with a specific stimulus multiple times
- The signals are averaged out so extraneous signals diminish and the signal related to the event remains
- By removing the background noise of general brain activity, researchers can see which electrical activity occurred in response to the vent
what are the strengths of post-mortem studies
- Post-mortem evidence was vital in providing a foundation for early understanding of key processes in the brain
- Both Broca and Wernicke relied on PM studies in establishing links between language, brain and behaviour
- help improve medical knowledge and help generate hypotheses for further study
limitations of post-mortem studies
→ Causation is an issue with these investigation
→ Observed damage to the brain may not be linked to the deficits under review but to some other unrelated trauma or decay
→ PM studies raise ethical issues of consent from the patient before death
- May not be able to provide informed consent
strengths of MRIs/fMRIs
- High spatial resolution (detailed)
- No radiation and non-invasive so fewer risks
limitations of MRIs/fMRIs
→ Low temporal resolution (5 sec time lag)
→ Expensive
→ Patient must be completely still, so limited range of stimuli/response can be measured e.g. sleep
Not always possible to replicate some activity in the scanner
strengths of EEGs
- EEGs are important in the diagnosis of conditions such as epilepsy
- Similarly, it has contributed much to our understanding of the stages involved in sleep
- extremely high temporal resolution
- Todays EEG technology can accurately detect brain activity at a resolution of one millisecond
limitations of EEGs
→ EEGs tend to produce very generalised information so it is not useful for pinpointing the exact source of neural activity
→ EEGs do not allow researchers to distinguish between activity originating in different but adjacent locations of the brain
strengths of ERPs
- Partly address the limitations of EEG
○ ERPs bring much more specificity to the measurement of neural processes - they have excellent temporal resolution, especially when compared to fMRIs.
- widespread use in the measurement of cognitive functions and deficits
- Researchers have been able to identify many different types of ERP and describe the precise role of these cognitive functioning, including parts of working memory
limitations of ERPs
→ Critics have pointed to a lack of standardisation in the ERP methodology between different research studies, making it difficult to confirm findings
→ A further issue is that in order to establish pure data in ERP studies, background noise and extraneous material must be completely eliminated, which is not always easy to do
