Brain Scanning Techniques


CAT scans (AO1)

  • Cat scans use multiple X rays to produce a cross sectional diagram of brain regions 
  • Stands for Computerised Axial Tomography 
  • The scans are interpreted by a computer and a detailed image of the structure of the brain can be seen 
  • Useful for detecting areas of brain damage following an accident or the positioning of tumors  in the brain
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Strengths of CAT scans (AO3)

  • They are quick to conduct and give accurate details of brains structures, which can help guide clinicians in descion making regarding treatment or surgery 
  • May help a surgeon better plan a procedure before surgery by being accurately to see the layout of brain structures before physically entering the skull. Makes the procedure faster and more efficient, reducing the risks associated with anaesthesia. 
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Weaknesses of CAT scans (AO3)

  • Can be considered unethical as exposure to radiation could cause physical harm
  • Brain scanning lacks ecological validity as it takes place in an artifical environment. 
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fMRI scans (AO1)

  • Picks up on changes in the brain depending on the task being carried out 
  • Blood flow and neuronal activity are linked, so changes in blood flow relate to neuronal activity, blood flow is used to show cell use of energy
  • Can look at differences in blood flow with accuracy and is useful for issues like strokes
  • Inside the magnetic field the nuclei in hydrogen molecules align themselves in terms of the magnetic field
  • As neural activity increases in the brain, blood flow increases in active areas to keep up the demand of oxygen
  • The haemoglobinn which carries oxygen repels the magnetic field (diamagnetic), when the blood is deoxygenated it follows the direction of the magnetic field (paramagnetic), both these changes are detcetd by the scanner and produces a computerised image
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Strengths of fMRI scans (AO3)

  • fMRI's are safer than other scans as there is no invasion, surgery or radiation needed, this is a strength becasue it means they are more ethical as no physical harm occurs
  • They are very precise in their data and with the brain being complex, precision is required when it comes to finding out about the brain structure/function. This is a strength beacuse it means there is reliability of the image and the data. 
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Weaknesses of fMRI scans (AO3)

  • It cannot measure the brain at rest so there is no baseline measure and its hard to pinpoint actual functioning for a specific activity-the brain is always active in more than one area. 
  • Cannot look at the actual receptors of neurotransmitters whereas PET scans can
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PET scans (AO1)

  • Stands for Positron Emission Tomography 
  • It investigates brain activity when a human is performing a task 
  • Involves injecting the patient with a small amount of radioactive material (tracer)
  • Once the tracer is absorbed a task may be given to stimulate the brain 
  • The radioactive atoms start breaking down emitting positrons which produces gamma rays which are picked up by the scanner 
  • Areas of low activity have fewer gamma rays which may show abnormal activity
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Strengths of PET scans (AO3)

  • Raine et al (1997) found differences in murderers brain activity using PET scans
  • Useful for investigating areas of the brain that are not functioning normally, which could indicate damage or tumours. 
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Weaknesses of PET scans (AO3)

  • Brain scanning lacks ecological validity as it takes place in an artifical setting 
  • Frequent exposure to radiation could mean brain scanning techniques could be unethical and it is unclear as to whether there are any long term affects 
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