Ways of studying the brain

• What are the 4 ways of studying the brain?

  • fMRIs
  • ERPs
  • EEGs
  • Post-mortem examinations
• What are the 3 ways of scanning the brain?

  • fMRIs
  • ERPs
  • EEGs
• What is an fMRI?

  • Functional magnetic resonance imaging
  • Large magnet
  • Scanning method = BOLD contrast -> Blood Oxygen Level Dependent
• How do fMRIs work?

  • Based on principle of active neurons requiring more energy = glucose + oxygen = more blood flow directed to active areas (haemodynamic response)
  • fMRI applies powerful magnetic field to subject -> radio waves 'bounce back' from brain tissue
  • Oxygenated + deoxygenated haemoglobin = diff. magnetic fields = diff. radio waves produced -> active/less active areas of brain can be mapped
  • Radio waves collected to generate 3D image of brain reflecting active/less active areas
• What do fMRIs tell us?

  • Show which parts of brain = active during specific tasks
  • Allows correlation between functioning areas of brain + tasks undertaken during scan
  • Latency of c.5 seconds
  • Spatial resolution = c.1 millimetre
• What are the strengths of fMRIs?

  • Much better spatial resolution than EEGs/ERPs -> narrow brain function to c.1mm
  • Able to show functioning no matter what area of the brain it is in, e.g. limbic system = superior to EEGs/ERPs -> more conclusions can be reached about which parts of brain are responsible for behaviour
  • fMRIs superior to other scanning + non-scanning techniques too, e.g. MRIs can show brain with same level of detail but don't show same level of functioning = no way of showing how activity impacts behaviour
• What are the weaknesses of fMRIs?

  • fMRIs measure blood flow in the brain, not activity itself = we must infer neuronal info = no conclusions can be drawn about neuronal activity's nature
  • Inferior to EEGs/ERPs for temporal resolution -> other scanning methods = near real time, while fMRIs are up to 5 seconds behind = brain activity shown occurs 5 seconds after task performed
  • fMRIs can only provide correlational conclusions about brain functioning -> we can see behaviour performed + blood flow in brain but we cannot ensure a causal connection
• What is an EEG?

  • Electroencephalogram
  • Electrodes placed on scalp to measure general brain activity
• How do EEGs work?

  • Electrodes placed on scalp
  • Measure electrical activity (action potentials) of neurons directly below electrodes
  • Detect + record activity of millions of neurons = general picture of overall activity
  • More electrodes = fuller picture
• What do EEGs tell us?

  • General brain activity in real time
  • Synchronised patterns in brain waves
  • Desynchronised patterns in brain waves
  • Latency only up to 1 millisecond
  • Can reveal certain neurological disorders, e.g. epilepsy = spikes of electrical activity, brain injury = slower patterns
• What are the strengths of EEGs?

  • EEGs better at showing dynamic brain activity than fMRIs -> temporal resolution of less than 1 ms = show brain activity in nearly real time
  • EEGs much cheaper than fMRIs (thousands rather than millions of £) = more easily accessible for research -> more research can be undertaken + verified
• What are the weaknesses of EEGs?

  • EEGs can only provide psychologists with a limited range of understanding -> measure general brain activity rather than specific neuronal activity = terrible spatial resolution = impossible to find where brain waves originate
  • EEGs can't give insight into activity below neural cortex -> only measure faint electrical pulses of action potentials being generated directly below electrodes = can't see activity deeper in the brain, e.g. regulation of emotions in limbic system
  • EEGs only give correlational conclusions between behaviour + brain activity
• Name the types of brain waves:

  A) Gamma

  B) Beta

  C) Alpha

  D) Theta

  E) Delta

  
• What is an ERP?

  • Event-related potential
  • Statistical analysis of hundreds of readings of EEG raw data
• How do ERPs work?

  • Statistical analysis of ERP raw data
  • Stimulus presented 100s of times
  • Each time stimulus is presented -> it's 'time-locked' = precise time of presentation noted
  • Meanwhile, brain activity measured with EEG
  • Recordings of time-locked periods superimposed on top of each other
  • Computer adds them together + cancels out background electrical activity = 'statistical averaging'
  • ERPs emerge
• What do ERPs tell us?

  • Specific brain waves responsible for specific functions
  • Latency = fraction of a millisecond = reveal early stages of cognitive processing
  • e.g. Sensory ERPs = within first 100 ms, cognitive ERPs = post-100 ms
  • General area of cortex involved
• What are the strengths of ERPs?

  • Based on EEG data = share strengths of EEGs -> much better at showing dynamic brain activity than other scanning methods + temporal resolution of less than 1 ms = brain activity shown in nearly real time compared to lag of fMRIs -> AND, ERPs = cheaper than fMRIs, too
  • ERPs = only way of studying brain that enable causal relationships to be drawn between brain activity + behaviour -> researchers can create IV by repeatedly presenting stimulus + using averaging to identify direct effect on brain activity (DV)
• What are the weaknesses of ERPs?

  • Based on EEG technology = only provide psychologists with limited understanding -> measure general brain activity rather than specific functioning due to terrible spatial resolution -> impossible to find out from where brain waves originate
  • ERPs give no insight into activity below neural cortex -> only measure faint electrical impulses of action potentials generated directly below electrodes = unable to tell us anything about neural activity controlling important functions deeper in brain, e.g. regulation of emotions in limbic system
• What are post-mortem examinations?

  • Visual examination of a chemically treated brain after death to find connections between abnormality in the brain and abnormal behaviour during life
• How do post-mortem examinations work?

  • Observable atypical behaviours studied while subject is alive
  • Neurobiology studied after death
  • Brain surgically removed + systematically dissected to investigate differences between brains
  • Brain investigated for anomalies (damage or difference from other brains, e.g. schizophrenia often = enlarged ventricles)
  • Anomalies/characteristics of deceased brain correlated with unusual living behaviours
• What do post-mortem examinations tell us?

  • Location of damage in brain
  • Brain structure correlated with specific behaviours, e.g. Broca (1861) or Annese et al. (2014)
• What are the strengths of post-mortem examinations?

  • Responsible for much biopsychological knowledge in Psychology -> without post-mortem examinations we would struggle to make such breakthroughs that enable our understanding of brain processes like language + memory = huge contribution to Psychology!
  • Post-mortems have improved as technology has advanced + are more advanced than scanning techniques in many ways -> enable detailed examinations of neuroanatomy + neurochemistry, e.g. staining can give more insight into functioning areas of brain than fMRIs + all areas of brain can be studied
• What are the weaknesses of post-mortem examinations?

  • Can never be conducted on functioning brain -> any conclusions drawn can only be correlational + retrospective because subject is no longer alive = no follow-up studies can be done -> no way to conduct further exam of functioning brain to test conclusions
  • Can't be sure that condition of deceased brain is similar to how it was in life, e.g. cause of death may have affected brain (e.g. stroke) + any treatments given at end of life/time delay could affect brain, too
  • Only correlational conclusions can be drawn because the person has died!