ways of investigating the brain

• Function Magnetic Resonance Imaging (fMRI)

  - uses large magnets to detect the oxygenated blood

  - produces 3D images showing which part of the brain is active

  - works by detecting changes in blood oxygenation and flow occurring

  - more active an area is , more oxygen is used

  - to meet the demand blood flow is directed to the active area (haemodynamic response)
• What does an fMRI aid our understanding of?

  localisation of function
• strengths of fMRI's


  - risk free

  - non-invasive

  - easy to use

  - images have high spatial resolution (depicts detail by the mm)

  provides clear image of brain localisation

  - doesn't use radiation
• weaknesses of fMRI's


  - expensive compared to others

  
  

  - patients have to be completely still

  
  

  - poor temporal resolution

  - there's a 5 second lag time between image taken and the firing of a neuron

  
  

  - only measures blood flow in the brain

  - not individual neurons which means its difficult to tell what kind of brain activity is being represented
• electroencephalogram (EEG)


  - measures electrical activity in the brain using electrodes that are on the scalp

  - scan recordings shows brainwave patterns from actions of millions of neurons

  - provides an overall account of brain activity

  - used to diagnose neurological abnormalities ( epilepsy , tumours , sleep disorders etc)

  - this is due to unusual arrhythmic patterns of activity
• strengths of an EEG

  - good for diagnosing disorders (epilepsy)

  - which involves random bursts of activity that can be easily detected

  
  

  - contributed to our understanding of the stages of sleep

  
  

  - very high temporal resolution

  - can accurately detect brain activity at a resolution of a millisecond
• weaknesses of an EEG

  - information received is generalised as it relates to thousands of neurons so we cannot say which neuron

  - doesn't allow researcher's to distinguish between activities originating in different but adjacent locations
• Event-related Potentials (ERP's)


  - uses the same technique as an EEG but it records when there's an activity in reaction to a stimulus

  - stimulus is presented multiple times and provides data using statistical analysis

  - what is left = ERP's which is brainwaves triggered by particular events

  - many types such as attention perception
• strengths of an ERP


  - neural responses are measured a lot more than in an EEG due to excellent temporal resolution

  - widespread use in the measurement of cognitive functions and deficits

  
  

  - many types have been identified

  - for eg. - P300 component is thought to be involved in the allocation of attentional resources and maintenance of the working memory
• weaknesses of an ERP

  - lack of standardisation in ERP methodology makes it difficult to confirm findings

  - background noise and extraneous material need to be eliminated which is not always possible
• post-mortem examinations


  - analysis of the brain after death

  - those who have a rare disorder or experienced unusual deficits in mental processes or behaviour are likely to have a post-mortem examination

  - damaged areas are examined to try and establish a likely cause and it can involve the comparison of a typical brain
• strengths of post-mortem examinations

  - Broca and Wernicke both relied on post-mortem studies in establishing links between language , brain and behaviour before brain imaging which was key to our early understanding of how the brain works

  - improves medical knowledge

  - helps to generate hypothesis for future studies
• weaknesses of post-mortem examinations

  - damage observed may not be linked to the disorder they are reviewing but linked to unrelated trauma or decay

  - ethical issues of consent from patient before death

  - patients may not be able to provide informed consent due a condition