scanning techniques

• fMRI – Produces a 3d scan of the brain, which shows the movement of blood, which is linked to activity of certain brain areas, when performing a task. Non-invasive technique with no radiation.

  + High spatial resolution, down to a single mm

  -Have low temporal resolution, 1-4 seconds

  -Have to stay perfectly still during the scan
• ERP – Event related potentials, work similar to EEGs but a stimulus is presented to patient, and therefore there is greater specificity in brain regions seen. Those detected within 100ms are classified as sensory and those that are detected after 100ms are termed cognitive. Non-invasive technique

  + High temporal resolution, down to a single ms

  + More specific than EEGs in terms of temporal resolution

  • Still relatively poor temporal resolution, not as good as fMRIs

  -Any extraneous variables such as outside sounds need to be eliminated, which cannot always be possible in uses of diagnoses in hospitals, where people are always going by.
• Post mortem – individuals with unique or atypical behaviours during their life are examined after their death. This allows for any damage to the brain to be identified. Non-invasive and patient is already dead.

  + Spatial resolution allows for deep brain areas to be investigated

  + Can improve our understanding of certain brain areas, and overall brain structure

  + Can generate hypotheses about certain brain area function (e.g. Tan)

  • Cannot establish causation, don’t know if the behaviour is a result of the abnormal brain, or the abnormal behaviour is results in the abnormal brain
  • Could be considered unethical with individuals like HM not being able to properly consent to the post-mortem due to his memory loss.
• fMRI works by detecting the changes in blood oxygenation and flow that occur as a result of neural activity specific parts of the brain. When a brain area is more active it consumes more oxygen and to meet this demand blood flow is directed to the active area. fMRI produces 3D images (activation maps) showing which parts of the brain are involved in a particular mental process, aiding our understanding of localisation of function.
• A strength of fMRI is that it does not rely on the use of radiation (as seen in other techniques such as

  PET scanning). The process is virtually risk-free, non-invasive and straight forward to use and produces

  highly detailed images, with detail depicted by the millimetre. This means that fMRI can provide a clear

  insight into how brain activity is localised without any negative implications for the patient.
• However, a limitation of fMRI is that it only measures blood-flow in the brain. It cannot look at the activity of individual neurons and so it can be difficult to tell exactly what kind of brain activity is being represented on the screen. Furthermore, fMRI may overlook the interconnectivity of brain sites. By only focusing on brain sites receiving increased blood flow, it fails to account for the importance of brain sites connecting/communicating with each other. These limitations therefore mean that fMRI only provides a partial account of brain activity, and further approaches may be required to gain a more comprehensive account.
• EEGs measure electrical activity within the brain via electrodes that are fixed to an individual’s scalp

  using a skull cap. The scan recording represents the brainwave patterns that are generated from the

  actions of millions of neurons, providing an overall account of brain activity.
• A strength of EEG is that it has been valuable in the diagnosis of a number of conditions. EEG is often used as a diagnostic tool as unusual patterns of activity may indicate neurological abnormalities such as epilepsy or tumours. For example, epilepsy is characterised by random bursts of activity in the brain which can easily be detected on screen. This is therefore a strength of EEG as it can provide a useful diagnostic tool when investigating disorders.
• However, a limitation of EEG is that is that only provides generalised information regarding the brain’s activity. The information relates to the activity of thousands of neurons and does not provide an

  indication of the exact source of neural activity. Furthermore, it does not allow researchers to distinguish between activities originating in different but adjacent locations. These limitations therefore mean that

  EEG only provides a partial account of brain activity, and further approaches may be required to gain a more comprehensive account.
• Neuroscientists have developed a way of isolating the neurological responses to the sensory, cognitive and motor events that are captured via EEG. Using a statistical averaging technique, all extraneous brain activity from the EEG recording is filtered out leaving only the responses that relate to a specific task. What remains are Event-Related Potentials (ERPs) – types of brainwave that are triggered by particular events.
• The main strength of ERPs is that they provide a more specific measure of neural processes than could previously be achieved with raw EEG measurements. Researchers have been able to identify many

  different types of ERP and describe the precise role of these in cognitive functioning. For example, the P300 component is thought to be involved in the allocation of attentional resources and the maintenance of working memory. This is therefore a strength of ERPs as they provide a more detailed and insight into neural functioning than standard EEGs alone.
• However, a limitation of the EEG/ERP technique is that it is potentially uncomfortable for the patient as electrodes are attached to the scalp. This could result in unrepresentative readings as the patient’s

  discomfort may be affecting cognitive responses to situations. It could therefore be argued alternative approaches such as fMRI, which is less invasive and would not cause discomfort, might lead to more accurate recordings.
• Post-mortems involved the analysis of a person’s brain following their death. In psychology this often involves those who have a rare disorder and have experienced unusual mental deficits during their

  lifetime. Areas of damage are examined after death as a means of establishing the likely cause of the disorder. This may involve comparison with a neurotypical brain to identify the extent of the difference.
• A strength of post-mortem studies is that they have provided a key source of evidence in our early understanding of processes in the brain. For example, both Broca and Wernicke relied on post-mortem

  studies in establishing links between language, brain and behaviour decades before neuroimaging became possible. Post-mortem studies therefore played an important role in the development of scientific understanding and continue to provide a valuable means of investigating brain function
• However, a limitation of post-mortem studies is that they do not necessarily provide a clear cause for a disorder. Observed damage to the brain might not be lined to the cognitive deficits under investigation - it is possible that damage in the brain might be due to some other unrelated trauma or decay. A range of other factors can also act as confounding variables such as length of time between death and post-mortem, age at death and drugs given in the months prior to death. This therefore limits the extent to which conclusions can be drawn from post-mortem studies as multiple variables will be present that could contribute to the appearance of the brain.