4. Ways of Investigating the Brain

• 1. Ways of Investigating the Brain

  Temporal Resolution:

  • accuracy of scanner in relation to time (i.e. how quickly scanner detects changes in brain activity).

  Spatial Resolution:

  • smallest feature that scanner can detect.
  • greater the spatial resolution allows discrimination between different brain regions w/ accuracy.
• 2. Ways of Investigating the Brain

  fMRI (Functional Magnetic Reasoning Imaging):

  • used measure activity while performing task.
  • does this by measuring changes in blood flow in areas of brain, using magnetic fields/radio waves.
  • they show increased neural activity in areas.
• 2a. Ways of Investigating the Brain

  fMRI:

  • when brain area more active, consume more oxygen.
  • to meet demand, blood flow directed to active area to deliver O2 in red blood cells.
  • amount of oxygenated blood changes + has magnetic signature - detected by fMRI.
  • speed they return to original position, measure amount of oxygenated haemoglobin = can produce maps showing which brain areas involved in certain mental activity.
• 2b. Ways of Investigating the Brain (Evaluation)


  fMRI - Strengths:

  • no radiation; risk-free + non-invasive.
  • accuracy produces images w/ high spatial resolution (1-2mm).
  • shows how brain activity localised.

  fMRI - Limitations:

  • expensive.
  • only captures clear image if person perfectly still.
  • poor temporal resolution (5-sec time lag).
  • only measure blood flow in brain, not neural activity, so can’t tell exactly what brain activity represented.
• 3. Ways of Investigating the Brain

  EEG (Electroencephalogram):

  • measures electrical activity in brain, via electrodes placed on scalp (skull cap).
  • detect small electrical charges from neural activity (i.e. measures neurons’ activity).
  • scan recording represents brainwave patterns, generated from action of millions of neurons = account of brain activity.
  • recording of general brain activity linked to states like sleep/arousal.
• 3a. Ways of Investigating the Brain

  EEG:

  • often used by clinicians as diagnostic tool.
  • unusual arrhythmic patterns indicate neurological abnormalities (e.g. epilepsy).
• 3b. Ways of Investigating the Brain (Evaluation)

  EEG - Strengths:

  • high temporal resolution (every millisecond).
  • invaluable in diagnosis of conditions like epilepsy.
  • contributed to understanding of sleeping stages (ultradian rhythms); real-life app.

  EEG - Limitations:

  • low spatial resolution; generalised info about areas of brain - difficult pinpoint certain areas of causation.
  • can’t distinguish between activities originating in diff but adjacent locations.
• 4. Ways of Investigating the Brain

  ERPs - Event-Related Potentials:

  • ERPs are types of brainwave triggered by particular events.
  • in its raw form, EEG overly general measure of activity.
  • statistical averaging technique, extraneous brain activity (from original EEG recording) filtered out, leaving responses relating to specific stimulus (ERPs).
• 4a. Ways of Investigating the Brain

  ERPs:

  • to filter extraneous activity, presentations of specific stimulus + the responses are averaged together.
  • extraneous neural activity won‘t occur consistently whereas activity linked to stimulus will.
• 4b. Ways of Investigating the Brain (Evaluation)

  ERPs - Strengths:

  • more specificity to measurements of neural processes than EEG can achieve alone.
  • high temporal resolution (derived from EEG measurements) = widespread use in measuring cognitive functions; identify diff types of ERP + role in cog functioning.

  ERPs - Limitations:

  • lack standardisation in ERP methodology between diff studies, difficult to confirm findings.
  • to establish pure data in studies, background noise + extraneous material MUST be removed completely, not always possible.
• 5. Ways of Investigating the Brain

  Post-Mortem Examination:

  • brain analysed after death to determine whether behaviours in patient’s life linked to abnormalities in brain.
  • used when person likely has disorder and experienced unusual deficits in mental process/behaviour.
  • areas of damage examined after death, establish case of affliction.
  • comparison to neurotypical brain.
• 5a. Ways of Investigating the Brain (Evaluation)

  PME - Strengths:

  • vital in providing foundation for early understanding of brain.
  • Paul Broca + Karl Wernicke relied on post-morterms in establishing links between language, brain + behaviours decades before neuro-imaging possible.
  • improve medical knowledge + generate hypotheses for new study.

  PME - Limitations:

  • causation issue; damage may not link to deficits but other unrelated trauma/decay.
  • ethical issues; informed consent (e.g. case of HM, no consent).