A03 - Ways of Investigating the Brain

• ✓Strength of fMRI


  • One of the strengths of fMRI is that it has high spatial resolution. This refers to the number of pixels in the digital output of the brain activation maps that are produced.
  • As fMRI has a greater number of pixels than some of the other techniques (showing detail by millimetre), the image/data that is produced is clear, detailed and gives a very good picture of brain localisation (produces images with high spatial resolution).
  • Making it much more useful when diagnosing illnesses such as stroke which can’t be detected from other techniques.
• ✓Another Strength of fMRI


  • Another  Strength of fMRI is that it is risk-free. Unlike other scanning techniques (e.g. PET), fMRI does not rely on the use of radiation and is safe. This means fMRI can safely provide a clear picture of how brain activity is localised.
• メWeakness of fMRI


  • fMRI are less successful when it comes to temporal resolution (low temporal resolution).
  • This is the difference between the neural activity occurring and the image appearing on the screen. As there is around a 5 second time lag between a neuron firing and the output being displayed (initial neural activity and image).
  • This means fMRI may not truly represent moment-to-moment brain activity. Meaning with fMRI it is more difficult to be certain whether the activity being viewed is a direct response of the stimulus. Creating an issue of validity.
• メ Another weakness of fMRI


  • Limitations of fMRI are that it is expensive. fMRI is expensive compared to other techniques. 
• ✓ Strength of EEG


  • EEG has practical uses and is particularly useful for diagnosing illnesses where there is abnormal brain activity.
  • For example, epilepsy can easily be detected using this method and stages of sleep are easy to analyse and EEGs has contributed to our understanding of the stages of sleep.
  • This shows the real-world usefulness of the techniques.
• ✓ 2 Strengths of EEG


  • As EEG equipment is much cheaper than fMRI this makes it a much more accessible technique when illnesses such as epilepsy or sleep disorders are suspected.
  • ALSO it also has high temporal resolution. This is the difference between the neural activity occurring and the image appearing on the screen - EGGs show brain activity in one millisecond.
• メWeakness of EEGs

  • EEG has low spatial resolution.
  • This refers to the number of pixels in the digital output of the brain activation maps that are produced.
  • The output from an EEG examination is a series of brainwave patterns holding little information about the location of such activity and is generally considered quite crude.
  • So although it is useful for specific illnesses such as epilepsy, it has limited use when trying to investigate more complex brain behaviour.
• メ Weakness of EEGs


  • Limitations of EEG is that information is generalised and the source of the information is not pinpointed.
  • The EEG produces a generalised signal from thousands of neurons and it is difficult to know the exact source of neural activity.
  • Therefore EEG can not distinguish the activity of different but adjacent neurons.
• ✓ Strengths of ERPs


  • An advantage of ERPs (and EEGs) is that it is non-invasive.
  • Unlike other scanning techniques, such as PET it does not use radiation or involve inserting instruments directly into the brain.
  • This means it is virtually risk-free and consequently, more patients will be open to it.
  • This will in turn allow more dysfunctional brains to be studied and understanding of the causes of such dysfunction to be improved.
• ✓ Strengths of ERPs

  • Strengths of ERP are specificity and good temporal resolution.
  • Measures of neural processes are more specific with ERPs than EEGs. ERPs also have excellent temporal resolution, better than fMRI.
  • This means that ERPs are frequently used in cognitive research due to them having higher validity.
• メWeakness of ERPs

  • Lack of standardisation in ERP methodology & there background ‘noise’.
  • 10-20 electrode placements commonly used but it been suggested use more electrodes = help improve spatial resolution. Lack of standardisation makes it difficult to confirm findings in studies involving ERPs.
  • Drawback of using larger numbers of electrodes to measure entire scalp is increase of interference & noise, which must be appropriately dealt with - tricky to eliminate.
  • Background ‘noise’ & extraneous material must be eliminated. These issues problem coz they not always easy to eliminate.
• ✓ Strengths of Post Mortems

  • Post mortems had large part to play in development of neuroscience, in medical research (they allow localisation - see where things are)
  • E.G. Broca & Wernicke relied on post mortems to develop their understanding of the language centre. They used Post-Mortems to link HM’s memory deficits to damage in his brain
  • Wernicke observed that the brains of aphasic stroke sufferers showed lesions in the left hemisphere, allowing him to identify Wernicke’s area.
  • So despite limited usage of them today, they greatly contributed to our understanding of brain.
• メWeakness of Post-Mortems

  • One of biggest issues using post mortem to understand illness is that it's difficult to ascertain whether damage to brain was a cause of the illness or a symptom of the illness. Limitations is causation - the observed damage in brain may not be linked to the deficits under review.
  • E.g. Post mortems of sz sufferers illustrate how they had particularly enlarged ventricles.
  • However,  is this what caused their symptoms or did reduced brain tissue mean their ventricles were abnormally large?
  • Such issues of causality limit application of this technique today.
• メ Weakness of Post-Mortems


  • Ethics.
  • Post-mortem studies raise ethical issues of consent after death (e.g. HM).
  • This challenges their usefulness in psychological research.
• Evaluation Points for Ways of Investigating the Brain

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• Evaluation Points for Ways of Investigating the Brain

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• Evaluation Points for Ways of Investigating the Brain?

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