Studying the brain

What are fMRIs used for

• establishing localisation of function

• Identifying parts of the brain involved in cognitive activities

How do fMRI scans measure brain activity

detect differences in blood flow as indicated by oxygen levels, which indicate which areas are more active

Do fMRIs have good spatial resolution?

• Yes, they can identify precisely where activity occurs

• So we are able to identify localisation of function to a precise degree and enhance our understanding of brain functioning

Do fMRIs have good temporal resolution

• No, they cant identify precisely when activity occurs

• Becomes a problem if researchers want to track brain activity over small time scales

Identify 2 reasons why fMRIs might not e used as often as researchers might want

• expensive and based in hospitals

• some people find them scary to be in (especially children)

• This limits the generalisability of the research

• Small sample sizes will reduce population validity

What are EEGs used for

To produce a record of the amount of brain activity in the form of brain waves

How do EEGs measure brain activity

• EEGs measure the electrical activity of neurons

• Electrodes placed on the skull

Do EEGs have good temporal resolution

• Yes, they record electrical activity without any delay

• So timings and changes can be clearly identified

Do EEGs have good spatial resolution

• No, they only record activity of the whole brain not its parts

• So you cannot identify where activity occurs, so you can’t identify localisation of function

What’s a limitation of EEGs

• Can’t identify specific shape of brain waves associated with specific mental activities when awake

  • since there’s so many activities, it’s impossible to isolate

• Which restricts the range of topics that can be studies

• So only really useful during sleep or when wave shape is very distinctive

What are ERPs used for

• ERPs used to identify shapes of brain waves that result from a stimuli

How do ERPs work

• Use standard EEG data but use a stimuli to produce a response and statistical techniques to isolate the response

Why are ERPs better at measuring the shape of brain waves associations with specific mental activities than EEGS

• ERPs give same task numerous times then average results

• So random brain activity noise is cancelled out

Why can ERPs be used for a much wider range of topics than EEGs

• can test reactions to stimuli when awake, unlike EEGs

• ERPs can use statistical averaging to isolate brain waves, so more topics apart from sleep can be researched

What are 2 limitation of using ERPs

• Lack of spatial resolution, as the electrodes record the whole brain, not specific parts

• Unable to identify specific shape of brain waves associated with specific cognitive functions, as there are too many variables it’s impossible to control

What do post-mortems do

• Suggest brain areas responsible for cognitive deficiencies and identify localisation of function

How do post-mortems work

• Natural experiment

• Examining brain of individuals who showed cognitive / behavioural deficits

• Identifying areas of damage, which suggest areas responsible for deficiency

• Compare to undamaged brains / ordinary functioning

What are some limitations of post-mortems

• Lots of time may have passed since the damage, so it’s hard to tell if the most obvious area of damage was responsible for that aspect of functioning

• Opportunities to test hypotheses is limited:

  • Hard to give consent if brain-damaged and impossible after death

  • Brain damage is relatively rare, especially localised damage

• Small samples reduce the generalisability of results