Studying the brain

• fMRI - Functional Magnetic Resonance Imaging


  Uses magnetic field and radio waves to detect changes in blood oxygenation and flow that occurs due to neural activity

  
  

  When an area of the brain is more active it consumes more oxygen - it also has more blood flow which is directed to the active area (haemodynamic response)

  
  

  Produces a 3D image of the brain, highlighting the active parts that are involved in a particular mental process
• fMRI - Strengths

  • It doesn't rely on radiation, so it is non-invasive and risk-free
  • Images are in high resolution - high accuracy
• fMRIs - Weaknesses

  • Expensive
  • Poor temporal resolution - 5-second lag between neural activity and image. So, it may not represent moment-to-moment brain activity accurately
  • Can only capture a clear image if the person stays still
• EEG - electroencephalogram


  • Measures electrical impulses produced by the brain through electrodes that are fixed to the persons scalp - skull cap
  • The scans that are recording shows the brainwave patterns generated from millions of neurons
  • Used as diagnostic tool - for example, any unusual arrhythmic patterns may indicate abnormalities like epilepsy or tumours
• EEG - Strengths

  • Invaluable in indicating neurological abnormalities - to diagnose conditions such as epilepsy or sleep disorders. This is a safe way of measuring brain activity, there is surgery or invasive process involved.
  • Contributes to our understanding of the stages of sleep
  • Extremely high temporal resolution - can detect brain activity at a resolution of a millisecond
• EEG - Weaknesses

  • Receives information from thousands of neurons - produces a generalised signal
  • This signal is not useful for pinpointing exact source of neural activity
  • Does not allow researchers to distinguish between activities originating in different but adjacent locations
• ERP - Event-related potentials


  A statistical analysis of EEG's

  
  

  Can filter out extraneous brain activities and isolate the responses that are relevant to a specific performance/task

  
  

  ERPs = types of brainwaves that are triggered by certain events
• ERP - Strengths

  • Excellent temporal resolution
  • More specific than using raw EEG data
  • Very specific measurements of neural processes
  • Has allowed researchers to identify many ERPs and state their exact role
• ERPs - Weaknesses

  • ERPs are small and difficult to pick out from other electrical activity in the brain - requires large amount of trials to gain meaningful data
  • Background noise and extraneous material must be completely eliminated to produce a 'pure' ERP reading
• Post-mortem


  A technique to analyse a person's physical brain following their death - to establish the underlying neurobiology of a particular behaviour

  
  

  Identifying areas of damage/abnormalities can help establish a cause to their condition
• Molaison


  An epileptic patient who suffered unexpected amnesia following surgery to the temporal lobes

  
  

  A post-mortem confirmed that his inability to store new memories was linked to lesions in the hippocampus
• 1840 - Tan


  A wordless patient is admitted to a hospital in Paris for aphasia - could understand spoken words but couldn't produce language expect for 'Tan'

  
  

  Broca meets him, and after his death, he performs an autopsy on Tan's brain.

  
  

  During the autopsy, Broca found a lesion of the brain up behind the eyes - he concluded Tan's aphasia was caused by damage to this area

  
  

  This area became known as 'Broca's area
• Post-mortems - Strengths

  • Provide foundation for understanding the brain
  • Broca and Wernicke relied on post-mortem studies
  • Improved medical knowledge and help to generate hypotheses for future study
• Post-mortem - Weaknesses

  • Causation - observed damage in the brain may not be linked to deficits under review, but instead the cause being some other related trauma or decay
  • Ethical issues as cannot give informed consent