6. Brain Scans

• fMRI Scans

  • Detects changes in both blood oxygenation and flow that occur as a result of neural activity in specific parts of the brain
  • More oxygen is consumed when a brain area is more active, so to meet this demand, blood flow is directed to the active area - haemodynamic response
  • Produces 3D images showing which parts of the brain are involved in a particular mental process
• EEGs

  • Measures electrical activity in the brain via electrodes that are fixed to an individual's scalp using a skull cap
  • Scan recording represents the brainwave patterns that are generated from the action of thousands of neurons, providing an overall count of brain activity
  • Used by clinicians as a diagnostic tool as unusual arrhythmic patterns of activity may indicate neurological abnormalities such as epilepsy, traumas or some sleep disorders
• ERPs

  • General measure of brain activity (graphs and charts)
  • Using a statistical averaging technique, all extraneous brain activity from the original EEG recording is filtered out only leaving responses that relate to a specific stimulus or task performance
  • ERPs are the only things left - types of brainwaves that are triggered by particular events
• Post-mortem exams

  • Analysis of a person's brain after death
  • Brains subject to this in psychological research are likely to have a rare disorder and have unusual deficits in cognitive processes
  • Compared with a neurotypical brain
• Strengths of fMRI scans

  • Does not use radiation or involve inserting instruments directly into the brain unlike PET scans - ethics protection from harm, risk-free
  • Good spatial resolution of 1-2mm - allows psychologists to discriminate between different brain regions with greater accuracy, significantly greater than the other techniques such as EEG and ERPs
• Limitations of fMRI scans

  • Costly for the NHS to fund and maintain - EEGs and ERPs are significantly cheaper. Small sample sizes will negatively impact validity of research
  • Do not provide a direct measure of neural activity, instead they simply measure changes in blood flow. While any change in blood flow may indicate activity within a certain brain area psychologists unable to conclude whether this brain region is associated with a particular function
  • Poor temporal resolution of approx 1-4 seconds. For instance, EEG and ERPs have a temporal resolution of 1-10 milliseconds
• Strengths of EEGs

  • Non-invasive - EEG does not use radiation or involve inserting instruments directly into the brain, and is therefore virtually risk-free
  • HOWEVER - could be argued that EEG is uncomfortable for the participant, as electrodes are attached to the scalp. Could lead to unrepresentative readings as the patient’s discomfort may be affecting cognitive responses to situations
  • Cheaper techniques in comparison with fMRI scanning and are therefore more readily available so this should allow more patients/participants to undertake it
• Limitations of EEGs

  • Poor spatial resolution as EEGs only detect the activity in superficial regions of the brain and is unable to provide information on what is happening in the deeper regions of the brain (such as the hypothalamus)
  • HOWEVER - good temporal resolution. They take readings every millisecond, a temporal resolution of 1-10 ms. It can record the brain’s activity in real time as opposed to looking at a passive brain. This leads to an accurate measurement of electrical activity when undertaking a specific task
• Strengths of ERPs

  • Non-invasive - ERP does not use radiation or involve inserting instruments directly into the brain, and is therefore virtually risk-free. Could be argued that ERP is uncomfortable for the participant, as electrodes are attached to the scalp. Unrepresentative readings as the patient’s discomfort may be affecting cognitive responses to situations
  • Cheaper techniques in comparison with fMRI scanning and are therefore more readily available - this should allow more people to undertake EEG/ERPs, which could help psychologists to gather further data on the functioning human brain
• Limitations of ERPs

  • Poor spatial resolution - ERPs only detect the activity in superficial regions of the brain. Unable to provide information on what is happening in the deeper regions of the brain (such as the hypothalamus)
  • Good temporal resolution - take readings every millisecond, a temporal resolution of 1-10 ms. It can record the brain’s activity in real time as opposed to looking at a passive brain. This leads to an accurate measurement of electrical activity when undertaking a specific task
  • More experimentally robust method as it can eliminate extraneous neutral activity
• Strengths of post-mortem exams

  • Broca and Wernicke both relied on post-mortem studies in establishing links between language, brain and behaviour decades before neuroimaging ever became a possibility