ways of studying the brain

Question 1

what are the different ways of studying the brain?

Answer 1

• post mortems
• fMRI + MRI
• PET scans (not on spec)
• EEG’s
  -ERPs

Question 2

how do post mortems work?

Answer 2

• investigate the brain after death
• if persons had an affliction in their lifetime= their brain may be acquired + investigated
• any damage found= we can link that part of brain to particular function –> may involve comparison to a healthy brain to see extent of difference

Question 3

strengths of post mortems?

Answer 3

• PM evidence= vital in providing foundation for early understanding of key processes in the brain
• Broca + Wernicke relied on PM studies in establishing links between language, brain + behaviour decades before neuroimaging
• PM studies= involve mental knowledge + help generate hypotheses
• can study brain without harming living person
  BUT to be ethical needs consent –> e.g. HM lost his ability to form memories + couldn’t provide consent but research was still carried out on his brain

Question 4

limitations of post mortems?

Answer 4

• causation= issue
• observed damage may not be linked to thing being reviewed –> may be due to other unrelated trauma + decay
• doesn’t reflect persons living brain + functioning

Question 5

how to PET scans work?

Answer 5

• allows us to see activity in brain
• person injected with radioactive glucose
• scan detects metabolism of substance and shows which parts of brain= most active in over a period of mins

Question 6

how to MRI’s work?

Answer 6

• allows us to investigate structure of brain
• strong magnetic waves sent through body= hydrogen atoms forced into different position + send out radio waves which scanner picks up an computer turns them into an image

Question 7

how do fMRI’s work (functional)?

Answer 7

• allows us to observe and measure brain function
• can see areas that are active (not only structure)
• works by detecting blood oxygenation to each area of the brain (more active areas require more oxygen)
  –> called the BOLD signal
• computer transforms info to a a 3D image + active + non-active areas can be compared as indicated by colouring of the area

Question 8

fMRI + MRI strengths?

Answer 8

• produces images with very high spatial resolution (they’re very detailed + provide clear pic of how brain active areas are localised)
• doesn’t use radiation + non-invasive= has fewer risks

Question 9

fMRI + MRI limitations?

Answer 9

• low temporal resolution (5 sec time lag between initial firing of neuronal activity + image on screens –> some important info may not be detected due to delay
• requires patient to be completely still (limited range of simuli/responses e.g. hallucinations)
• expensive= limited countries can afford

Question 10

how to EEG’s work?

Answer 10

• electrodes place on surface of skull (more electrodes= the more detailed) + they measure changes in electrical activity when person performs a task
• records activity from groups of neurons in the brain + it’s a crude measurement shown in waves –> type of wave shown= indicates part of brain performing task

Question 11

EEG strengths?

Answer 11

• important in diagnosis of conditions like epilepsy which is a disorder where random burst of activity in the brain can be detected
• has helped our understanding on stages involved in sleep
• unlike fMRI, EEG has high temporal resolution (almost instantineous –> can accurately detect brain activity in one millisecond)

Question 12

EEG limitations?

Answer 12

• EEG’s provide generalised info –> not useful for prompting exact source of neural activity + doesn’t allow researchers to distinguish between activities originating in diff but adjacent locations
• low spatial resolution
• only detects surface activity within accessible regions in brain –> don’t get insight on deeper regions of brain e.g. amygdala

Question 13

how do ERP’s work?

Answer 13

(event related potentials)
- same apparatus + techniques as EEG’s
- ERP’s= record activity in response to a stimulus (can be sensory, cognitive or motor events)
–> ppts undergo EEG’s + one presented with specific stimulus multiple times
–> signals are averaged out so extraneous signals diminish + signal related to event remains
–> background noise of general brain activity is remved so researchers can see which electrical activity occurred in response to the event

Question 14

ERP’s strengths?

Answer 14

• address limitations of EEG’s –> bring much more specificity to measurement of neural processes
• temporal resolution as ERP’s are derived from EEG measurements –> better than fMRI’s –> this has led to widespread use in measurement of cognitive functions + deficits –> researchers have identified many diff types of ERP’s + describe precise role of these cognitive functioning (including parts of working memory)
• cheaper than fMRI’s= more widely used

Question 15

ERP’s limitations?

Answer 15

• lack of standardisation in ERP’s methodology between different research studies= difficult to confirm findings
• to ensure raw data is collected all background noise + extraneous material must be removed (not easy to do)
• electrode cap may be uncomfortable= ppts may drop out of sample= smaller sample size + less data –> and if cap is uncomfy ppts may move it= alter validity of findings