Brain Scans

• PET Scans


  1. Use radioactive isotopes with a long half-life

  2. Isotope decays, emitting positrons which interact and combine with glucose or water molecules, forming radiotracers

  3. Increased radiotracers accumulate in highly active brain areas due to haemodynamic response

  4. Emitted gamma rays detected by the scan
• PET scans are very useful for the diagnosis and monitoring of progressive, neurodegenerative diseases, such as Alzheimer's (characterised by a reduction in glucose metabolism rates in the brain)
• fMRI scans


  1. Rely on the haemodynamic response

  2. Areas with high activity have higher deoxyhaemoglobin which absorbs the signal, appearing brightly coloured

  
• fMRI scans have high temporal resolution as up to 4 images can be produced per second
• fMRI scans can be used whilst a patient is carrying out a task, and so data from fMRI scans can help us to make inferences about brain function and localisation

  
• fMRI scans do not use ionising radiation, unlike PET scans, and so are safer
• EEG scans


  Use electrodes attached to the scalp to measure and amplify the electric activity across the whole brain
• EEG scans are particularly useful in investigating the characteristics of the different stages of sleep, as demonstrated by Dement and Kleitman
• EEG scans have much higher temporal resolution than fMRI scans, and so are more appropriate for the monitoring of ongoing cerebral states and activity

  
• EEG scans are useful in the diagnosis of epilepsy, which is characterised by random bursts of activity
• Post-mortem examinations


  1. Compare the patient's brain with that of a healthy, neurotypical brain

  2. Identify any differences (e.g. lesions, damage, abnormally large or small areas)

  
• Post-mortem examinations are particularly useful for advancing medical knowledge, and being the basis of further research into certain areas of the brain