Investigating the brain

What does fMRI stand for?

Functional magnetic resonance imaging

What does fMRI measure?

Blood oxygen level - when a brain area is more active, it consumes more oxygen to meet this increased demand

What type of images do FMRIs produce?

3D images showing which parts of the brain are involved in particular mental processes

What are some of the strengths of FMRI?

• does not rely on the use of radiation

• when used correctly it is risk-free, non-invasive and straightforward

• it produces images that have very high resolution, depicting detail to the milimeter

What are the weaknesses of FMRI?

• expensive compared to other neuroimaging techniques

• can only capture a clear image if the individual remains still

• it has a poor temporal resolution (5-second lag time behind the image and the initial firing of neural activity)

• it only measures blood flow in the brain making it difficult to tell exactly what kind of brain activity is happening

What does EEG measure?

Electrical activity in the brain

How is EEG recorded?

Electrodes placed on the scalp using a cap

What does the scan recording represent?

the brainwave patterns that are generated from the action of millions of neurons, producing an overall account of brain activity

What is EEG commonly used to diagnose?

Epilepsy and other unusual patterns of activity

What are the strengths of EEGs?

• invaluable in the diagnosis of conditions e.g epilepsy

• contributed much to our understanding of the stages involved in sleep

• unlike FMRI, EEG tech has extremely high temporal resolution meaning that it can accurately detect brain activity at a resolution of a single milisecond

What are the weaknesses of EEGs?

• poor spatial resolution - can’t accurately identify the exact brain area where activity is coming from

What does ERP stand for?

event-related potentials

What are ERPs?

Brain responses to specific stimuli

How are ERPs obtained?

By averaging EEG recordings. All extraneous brain activity is filtered out, leaving only responses that relate to the activity

Why is averaging useful?

Removes background noise

What are the strengths of ERPs?

• allow for much more specificity to the measurement of neural processes in comparison to EEG

• have excellent temporal resolutions compared to FMRIs

• researchers have been able to identify many diff types of ERP and describe the precise role of these in cognitive functioning

What are the weaknesses of ERPs?

• lack of standardisation in ERP methodologies, making it difficult to confirm findings

• difficult to achieve the elimination of background noise and extraneous material

What is a post-mortem examination?

Study of the brain after death. Involves examining the areas of damage within the brain as a means of establishing the likely cause of the illness the person suffered

What famous case supports post-mortems?

Broca’s patient “Tan”

What are the strengths of post-mortem?

• detailed examination of brain structure

• Broca and Wernicke both relied on post-mortems to establish links before neuroimaging was possible

• studies improve medical knowledge and help generate hypothesis for further study

What are the weaknesses of post-mortems?

• causation is an issue. Observed damage to the brain may not be linked to the conditions under investigation but to some other unrelated trauma

• can raise ethical issues of consent e.g HM was never able to provide consent