brain scans

• what is structural imaging

  produces a static image of the brain & deals with structure of nervous system e.g: CT scan
• what is functional imaging

  produces images of what the brain is doing or which areas are active during tasks e.g: PET scan, fMRI scan
• compare structural and functional brain imaging (3)

  structural produces static image of brain (CAT), functional produces images of active areas (PET) a similarity is both can provide insight into aggression when looking at murderes
• mechanism and measurement of CAT scan

  1. uses x-rays that pass through the brain in multiple angles - computer compiles images together creating cross-sectional images of brain showing structure
  2. shows what areas of the brain are damaged or positioning of tumours
• risks, usefulness and limitations of CAT scan

  • advantage: records images of bone, soft tissue and blood vessels simultaneously making exploratory surgery unnecessary
  • quick to conduct showing accurate details of brain structure
  • disadvantage: only tells you structural not functional information so limited use in research - which areas of brain are actively processing info unlike PET, fMRI scans
• mechanisms and measurements of PET scan

  1. patients are injected with FDG (radioactive tracer) that is absorbed into the bloodstream and binds to glucose molecules in the blood
  2. measures glucose usage in the brain and the more glucose in one area means area is more active
  3. produces images on a computer
• risks, usefulness and limitations of PET

  • advantage: can be used for diagnosis of brain diseases e.g: alzheimers which causes changes in brain metabolism, shows which parts of brain are active
  • disadvantage: FDG is radioactive so damages cells and tissues - scan can only be done once every 6 months, worse spatial resolution than fMRI
• mechanisms and measurements of fMRI scan

  1. uses radiofrequency energy & magnetic field to measure blood oxygen levels - most active areas will use the most oxygen
  2. blood cells with oxygen will repel magnetic field and blood cells without oxygen will follow the magnetic field
  3. changes to field measured by a computer as radio waves
  4. produces high resolution images
• risks, usefulness and limitations of fMRI

  • advantage: have better spatial resolution than PET scans when measuring brain activity. PET scans measure changes in blood flow in brain in an area of 5-10 cubic mm but fMRI can resolve down to 3 cubic mm
  • disadvantage: only measures oxygen consumption which is not a direct measure of brain activity, whereas PET scans directly measure parts of the brain which are active as it focuses on glucose consumption
• overall benefits

  • reliable and objective way to measure brain activity (O2 use or glucose usage) or structure
  • by comparing these measurements against observed behaviours, we can establish connections between brain areas and behaviours
• overall issues with using brain scans

  • tasks in brain scans have low mundane realism so may not trigger or activate the brain in the same way where a real behaviour would (e.g: tracking tasks on a computer vs actually being aggressive in real life such as being in a physical fight)