Ways of studying the brain Flashcards
why is brain imaging done
Techniques for scanning the brain are often used for diagnosing illness and in psychological research it is often used to investigate localisation.
Functional magnetic resonance imaging (fMRI)
FMRI works by 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, blood flow is directed to the active area. FMRI produces 3D images showing which parts of the brain are involved in a particular mental process. This has important implications for our understanding of localisation of function.
Strengths of fMRI
FMRI doesn’t rely on the use of radiation unlike PET. It is virtually risk free, non-invasive and straightforward to use. It produces images that have very high spatial resolution, depicting detail by the millimetre, and providing a clear picture of how brain activity is localised.
Limitations of fMRI
FMRI is expensive compared to other neuroimaging techniques. Poor temporal resolution as there is around a 5 second time lag behind the image on the screen and the initial finding of neuronal activity. FMRI imaging may not represent moment to moment brain activity.
Electroencephalogram (EEG)
EEG’s measure electrical activity within the brain via electrodes fixed to an individual’s scalp using a skull cap. The scan recording represents the brainwave patterns that are generated from the action of thousands of neurons, providing an overall account of brain activity. EEG’s are often used by clinicians to indicate neurological abnormalities such as epilepsy, tumours and sleep disorders.
Strengths of EEG
EEG’s are useful in studying the stages of sleep and in the diagnosis of epilepsy. Unlike fMRI, EEG has extremely high temporal resolution. They can accurately detect brain activity at a resolution of a single millisecond providing EEG’s with real world usefulness.
Limitations of EEG
With EEG’s there is a generalised nature of the information received. EEG signal isn’t useful for pinpointing the exact source of neural activity. They don’t allow researchers to distinguish between activities originating in different but adjacent locations.
Event-related potentials (ERPs)
A method of measuring brain activity in response to a stimulus. All extraneous brain activity from the original EEG recording is filtered out leaving only those responses that relate to the performance of a specific task. What remains are event-related potentials. ERPs are types of brainwave triggered by particular events. Research has revealed many different forms of ERP and how, for example, these are linked to cognitive processes such as attention and perception.
Strengths of ERPs
As ERPs are derived from EEG’s they have excellent temporal resolution, especially when compared to fMRIs. This means ERPs are frequently used to measure cognitive functions and deficits such as the maintenance of working memory.
Limitations of ERPs
There is a lack of standardisation in ERP methodology between different research studies. To establish pure data in ERP studies, background noise and extraneous material must be completely eliminated, which may not always be easy to achieve.
Post-mortem examinations
Post-mortem examinations are an analysis of a persons brain following their death. Areas of damage within the brain are examined after death as means of establishing the likely cause. They may involve comparison with a neurotypical brain to ascertain the extent of the difference.
Strengths of post-mortem examinations
Post-mortem examinations were vital in providing a foundation for early understanding of key processes in the brain. Post-mortem examinations were used to study HM’s brain to identify the areas of damage which could then be associated with his memory deficits.
Limitations of post-mortem examinations
Causation is an issue within these studies. Observed damage to the brain may not be linked to the deficits under review but to some other unrelated trauma. A further problem is that PME raise ethical issues of consent from the individual before death. Participants may not be able to provide informed consent, for example in the case of HM who lost his ability to form memories and was not able to provide such consent – nevertheless post-mortem research has been conducted on his brain. This challenges the usefulness of post-mortem examinations in psychological research.
