Ways of studying the brain

What are the main ways of studying the brain?

• fMRI (functional magnetic resonance imaging) → blood flow

• EEG (electroencephalogram) → electrical activity

• ERP (event-related potentials) → response to stimuli

• Post-mortem examinations → structural analysis after death

Each method differs in temporal resolution, spatial resolution, and application

What does fMRI measure?

• Measures blood flow (oxygenation levels) in the brain

• Increased blood flow = increased neural activity

• Produces 3D images showing brain localisation

• Used during cognitive or physical tasks

What are the strengths of fMRI?

• Produces high-resolution (up to 1mm) images

• Provides a dynamic picture of brain activity

• Non-invasive and does not use radiation

• Useful for identifying localised brain functions

What are the limitations of fMRI?

• Measures blood flow, not direct neural activity → indirect measure

• Poor temporal resolution (delay of ~5 seconds)

• Expensive and requires large, complex machinery

• Participants must remain completely still

• May ignore connectivity between brain regions

How does Lashley challenge localisation?

• Removed portions of rats’ cortex (10–50%)

• Found no specific area responsible for learning

• Suggested higher functions are distributed (equipotentiality)
  → Challenges strict localisation seen in fMRI studies

What does an EEG measure?

• Measures electrical activity of the brain via electrodes on the scalp

• Records brain waves over time

• Measures:

  • Amplitude: intensity

  • Frequency: speed of activity

What are the main brain wave patterns?

• Alpha: relaxed, awake

• Beta: alert, active, REM sleep

• Delta: deep sleep

• Theta: light sleep

What are the strengths of EEGs?

• Excellent temporal resolution (real-time activity)

• Tracks changes in brain activity over time

• Useful in diagnosing disorders (e.g. epilepsy, Alzheimer’s)

• Non-invasive and relatively cost-effective

What are the limitations of EEGs?

• Poor spatial resolution (cannot pinpoint exact location)

• Only measures activity in outer brain layers

• Cannot detect deep brain activity

• Difficult to distinguish between closely adjacent areas

What are ERPs and how do they work?

• Derived from EEG recordings

• Measure brain response to specific stimuli

• Use averaging across repeated trials to remove noise

• Identify consistent responses to stimuli

What are the two types of ERPs?

• Sensory ERPs: occur within 100 ms → initial detection of stimulus

• Cognitive ERPs: occur after 100 ms → processing and evaluation

What are the strengths of ERPs?

• Provide precise timing of brain responses (milliseconds)

• Allow direct measurement of processing of stimuli

• Useful for studying attention and perception

What are the limitations of ERPs?

• Same issues as EEG:

  • Poor spatial resolution

  • Cannot measure deep brain activity

• Requires many repeated trials → time-consuming

What are post-mortem examinations?

• Study of the brain after death

• Often used when individuals had abnormal behaviour or disorders

• Compared with neurotypical brains to identify differences

What are the strengths of post-mortem studies?

• Allow detailed study of deep brain structures

• Provide insights into rare disorders

• Not limited by scanning technology

What are the limitations of post-mortem studies?

• Cannot measure brain activity (only structure)

• Findings may be affected by confounding variables:

  • Time since death

  • Drug use before death

  • Brain damage unrelated to disorder

• Small, unrepresentative samples → low generalisability

• Largely replaced by modern brain imaging techniques

How do these methods compare in resolution?

• fMRI: high spatial, low temporal resolution

• EEG/ERP: high temporal, low spatial resolution

• Post-mortem: high structural detail, no functional data