Ways of investigating the brain Flashcards
What does fMRI stand for?
Functional magnetic resonance imaging.
How do fMRI’s work?
Detecting the changes in blood oxygenation and flow that occur as a result of neural activity in specific parts of the brain. When a brain area is more active it consumes more oxygen and to meet this increased demand, more blood flow is directed to the area (the haemodynamic response). fMRI produces 3-dimensional images (activation maps) showing which parts of the brain are involved in particular mental process- indicated by colour.
Strengths of fMRI’s.
fMRI’s, unlike other scanning techniques such as PET, do not rely on the use of radiation and if administered currently, are virtually risk free, non-invasive and straightforward to use. They also have very high spatial resolution, depicting detail by the millimetre so providing a clear picture of localised brain activity.
Limitations of fMRI’s.
fMRI’s are expensive compared to other neuroimaging techniques and can only capture a clear image if the person stays perfectly still.
Has poor temproral validity because there is around a 5-second time lag behind the image on screen and the initial firing of neuronal activity.
The technique can only measure blood flow in the brain not the activity of individual neurons so it does not tell us exactly what kind of brain activity is being represented on the screen.
What does EEG stand for?
Electroencephalogram.
How do EEG’s work?
EEG’s measure electrical activity within the brain via electrodes that are fixed to an individuals scalp using a skull cap. The scan recording represents the brainwave patterns that are generated from the action of millions of neurons, providing an overall account of brain activity. EEG’s are often used as a diagnostic tool as unusual patterns may indicate epilepsy, tumours or sleep disorders.
Strengths of EEG’s.
EEG’s have proved valuable in the diagnosis of conditions such as epilepsy, a disorder caused by random bursts of brain activity. They have contributed much to our understanding of the stages involved in sleep.
Unlike fMRI, EEG technology has extremely high temporal resolution. E.g of a single millisecond.
Limitations of EEG’s.
EEG’s have a generalised nature. The EEG signal is not useful for pinpointing the exact source of neural activity and it does not allow researchers to distinguish between activities originating in different but adjacent locations.
What does ERP stand for?
Event-related potentials.
What are ERP’s?
EEG’s are a development of EEG’s which filter out all extraneous brain activity and leave only the responses that relate to e.g the presentation of a specific stimulus or performance of a specific task. Event-related potentials are types of brainwaves triggered by particular events.
Strengths of ERP’s.
The limitations of EEG’s are addressed through the use of ERP’s.
They bring much more specificity to the measurement of neural processes. ERP’s are derived from EEG’s so they have excellent temporal resolution which has led to their widespread use in the measurement of cognitive functions.
Researchers have been able to identify many different types of ERP and describe their precise role in cognitive functioning.
Limitations of ERP’s.
In order to publish pure data in ERP studies, background noise an extraneous material must be completely eliminated, and this may not always be easy to achieve.
What is a post-mortem examination?
A technique involving the analysis of a persons brain following their death. In psychological research, individuals whose brains are subject to a post-mortem are likely to be those who have a rare disorder and have experienced unusual behaviour in their lifetime. Areas of damage within the brain are examined after death as a means of establishing the likely cause of the affliction the person experienced.
When would a post-mortem be used?
After death
Strength of post-mortem examinations.
post-morterm evidence has been vital in providing a foundation for early understanding of key processes in the brain. Paul Broca and Karl Wernicke both relied on post-mortem studies in establishing links between language, brain and behaviour decades before neuroimaging.
