Ways of studying the brain

• Post-mortem examinations: used to establish underlying neurobiology of behaviour. Researchers can look for physical abnormalities or damage to the brain after death.
• Examples of post-mortem examinations & support: Broca’s patient Tan had a lesion in his left frontal lobe, where Broca’s area is located (issues with speech production when alive). Schizophrenic patients had lighter brains due to ventricular enlargement.
• Issues with post-mortem examinations - Ethics

  -HM (lost ability to form new long term memories) did not consent for his brain to be studied after death. Breach of ethical issues.
• Issues with post-mortem examinations - many confounding variables affect identification of localisations (drug treatments, the stage of disease, extent of damage or age). Low generalisability.
• Benefits of post-mortem examinations

  + Allows more thorough and detailed look on neurochemical aspects of the brain - hypothalamus and hippocampus can be studied (cut into).
• fMRIs: measures changes in the brain activity while performing a task. Measured by changes in blood flow indicating neural activity in a particular area as more oxygen is required (haemodynamic response). Researchers can produce 3D activation maps showing cortical specialisations.
• Benefits of fMRIs

  + Risk free procedure, non invasive as there is not exposure to radiation Like PET scans.
• Limitations of fMRIs

  -Not a direct measure of neural activity, but a measure of blood flow - poor temporal resolution as does not show activity at the time of behaviour.
• Limitations of fMRIs

  -overlooks the interconnected communication of the brain as it focuses of localised activity. High spatial resolution.
• EEGs: measures electrical activity in the brain. Electrodes on the scalp detect small charges from the activity of brain cells. The result is graphed as an EEG trace.
• EEGs have identified four basic patterns of activity: alpha waves, beta waves, delta waves and theta waves. Alpha and beta waves are present during consciousness, during deep sleep delta and theta waves occur, and during REM sleep beta waves are present (brain mimics consciousness).
• Benefits of EEGs

  + provides real time activity of the brain rather than just a still image - accurately measures activity and the location of the brain it is associated with.
• Benefits of EEGs

  + Useful in the diagnosis of epilepsy by recording abnormal electrical activity. Seizures explained by sudden changes in brain activity.
• Limitations of EEGs

  -Does not reveal activity of lower regions of the brain (hypothalamus and hippocampus). This can be achieved by implanting electrodes within the brain but is not ethically permissible in humans.
• Limitations of EEGs

  -EEG signals are not always able to pinpoint an exact area of activity as there is interference from other activity in the brain.

  Makes it hard to distinguish between different areas in the brain. Low spatial resolution.
• ERPs: small voltage changes in the brain that are triggered by events/stimuli. To find a specific response to a stimulus, it is presented multiple times then averaged together. Activity not related to a stimulus will not be consistent.
• ERPs are divided into two categories: waves within 100 milliseconds of a presented stimulus are ‘sensory’ ERPs, and after 100 milliseconds are ‘cognitive’ as the ppt mentally processes the stimulus.
• Benefits of ERPs

  + More likely to pinpoint exact source of activity, researchers identify precise roles in cognitive function from many ERPs. Provides continuous measure of processing (high control).
• Benefits of ERPs

  + Has excellent temporal resolution and is used widely in the measurements of cognitive function and deficits.
• Limitations of ERPs

  -Time consuming; often difficult to identify specific activity from other activity in the brain, may take longer to process and analyse data.
• Limitations of ERPs

  -Electrical activity is restricted to only the upper cortex of the brain and does not reach into lower levels of the brain.