Studying the brain

• Spatial resolution is the level of accuracy in identifying the exact location of a brain structure or brain activity in space.
• Temporal resolution is the level of accuracy when identifying the exact location of where brain activity occurred in time.
• Post Mortem dissections:

  • Usually conducted on those who suffered trauma or had mental illness.
  • These are compared to a neurotypical healthy brain.

  Example case - Tan. Broca's area was discovered after a post-mortem dissection on Tan, who could only say Tan (expressive aphasia). Damage in an area of the frontal lobe was found after Tan's death.
• Strengths of post mortem dissections:

  • Practical application - This technique is useful in providing advancing medical knowledge. Broca and Wernicke both relied on post mortem examinations to create links between language and behaviour in the brain.
• Limitations of post mortem dissections:

  • Ethical concerns - Informed consent may not be given by the patient or the family. In HM's case, he suffered from deficits in his short-term memory, so he wouldn't remember signing for consent. This may mean that the consent given was not valid.
• fMRI (Functional magnetic resonance imaging):

  • Relies on haemodynamic responses.
  • Detects blood flow in the brain due to certain areas needing more blood when carrying our specific tasks.
  • These are compared to low activation areas with a lower blood supply.
• Strengths of fMRI scans:

  • Good spatial resolution - Approximately 1mm.
  • Non-invasive and safe because it does not rely on radiation (like PET scans) and so are safer.
  • Can be conducted when patients are carrying out tasks showing localisation in real time.
• Limitations of fMRI scans:

  • Poor temporal resolution - Resolution of 1-4 second difference from the activity being carried out and the picture being taken, resulting in psychologists being unable to predict with high accuracy.
  • Causation - fMRI measure changes in blood flow and so it is impossible to say what caused the change at a neural level.
• EEG (Electroencephalogram):

  • 22-34 electrodes that are attached to a cap and fitted to the scalp with conductive gel.
  • Displays brain waves from each individual electrode showing brain activity.
  • Amplitude (size of waves) show the brain wave intensity.
  • Frequency (distance between each wave) shows the speed of the activation.
• Strengths of EEG:

  • Practical application - Aids in diagnosis of epilepsy as the spontaneous bursts of brain activity can be easily detected.
  • High temporal resolution - Takes pictures every millisecond so accurate analysis can be conducted.
  • Non-invasive compared to other scans (eg PET scans). This reduces any risk of accidental damage to the brain and more patients agree to it.
• Limitations of EEG:

  • Poor spatial resolution - Only detect activity in superficial regions of the brain. So they are unable to provide information on what is happening in the deeper regions of the brain (such as the hypothalamus), making this technique limited in comparison to the fMRI.
  • False results - May be uncomfortable for patients leading to unrepresentative readings.
  • Difficult to accurately gather where the activity is coming from.
• ERP (Event related potentials):

  • Same technique as the EEG but presents a stimulus many times, creating a smooth curve of activation by combining data (through statistical averaging).
• Strengths of ERP:

  • Good temporal resolution - Researchers have identified different types of ERP and describe the precise role of these in cognitive functioning (eg - P300 component is involved in the allocation of attentional resources and the maintenance of working memory).
• Limitations of ERP:

  • Lack of standardisation - To establish pure data in ERP studies, background noise and extraneous material must be completely eliminated, and this may not always be easy to achieve.