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4 ways of investigating the brain
functional magnetic resonance imaging (fMRI)
electroencephalogram (EEG)
event-related potentials (ERPs)
post-mortem examinations
how does fMRI work?
it detects the changes in blood oxygenation and flow that occur as a result of neural activity in specific parts of the brain
what happens 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
what do fMRIs show us?
fMRI produces 3D images showing which parts of the brain are involved in important mental processes, this has important implications for our understanding of localisation
strengths of fMRI
virtually risk-free, non-invasive and straightforward to use. Unlike other scanning techniques it does not use radiation. It can be used to measure brain activity without causing harm
the images it produces have very high spatial resolution, showing detail by the mm. This provides a clear picture of how brain activity is localised.
weaknesses of fMRI
expensive compared to other neuroimaging techniques
can only provide an image if the person stays completely still
poor temporal resolution (doesn’t accurately show changes over time). The highlighted areas appear 4/5 seconds after the brain activity has occured- findings can be misinterpreted.
it can only measure blood flow in the brain, can’t tell us the exact activity of individual neurons. It can be difficult to tell what kind of brain activity is being represented
what do EEGs measure and how?
electrical activity in the brain via electrodes that are fixed to an individual’s scalp using a skull cap
what do the scan recordings represent?
brainwave patterns that are generated from the action of millions of neurons, providing an overall account of brain activity
what are the 4 types of EEG waves?
alpha, beta, theta, delta
amplitude
intensity or size of activity
frequency
speed or quantity of activity
why are EEGs used by clinicians?
as a diagnostic tool as unusual arrhythmic patterns of activity may indicate neurological abnormalities (e.g. epilepsy, tumours or sleep disorders)
strengths of EEG
valuable at helping diagnose conditions (e.g. schizophrenia and epilepsy) because the difference in brain activity can be detected on the screen- useful for clinicians
contributed to our understanding of the sleep stages and sleep problems - useful
extremely high temporal resolution (unlike fMRI), it records brain activity in real time. Researchers can monitor responses to tasks.
weaknesses of EEG
it cannot detect activity in deeper brain regions as it only represents brainwave patterns. Therefore, if there were issues to a patients hippocampus an EEG would not necessarily pick up on this.
not useful in pinpointing the exact source of neural activity so it is hard to work out which area ofthe brain the waves originate from
what is an ERP?
In an ERP a patient is presented with a stimulus (i.e. picture/sound) and researchers look for activity related to this stimulus and how an EEG wave pattern changes in response to the stimulus
what is the statistical averaging technique?
The stimulus is presented hundredes of the times and an average response is graphed. This reduces any extraneous brain activity, making the specific response to the stimulus stand out.
what has research revealed?
there are many different forms of ERPs and how these are linked to cognitive processes for example, such as attention or perception
strengths of ERPs
ERPs are much more specific to the meaurement of neural processes than EEGs, partly addressing the problem of EEGs being too general
they provide a continuous measure of processing in response to a stimulus, this provides quantitative experimental data
researchers have been able to identify ERPs of mental health issues, like phobias. People with phobias have ERPs of greater amplitude in response to images of objects they fear in comparison to non-phobic individuals. Gives researchers more of an understanding of complex mental processes
what is a post-mortem examination?
technique involving the analysis of a dead person’s brain
in psychology, whose brain might be used in a post-mortem?
those of individuals who have a rare disorder and have experienced unusual deficits in mental processes or behaviour during their lifetime
why do psychologists want to examine brains after death?
in order to establish the likely cause of the affliction the person wihh brain damage suffered. This may also include comparison with a typical brain in order to determine the extent of the difference between them.
strengths of post-mortem
post-mortem evidence was vital in providing a foundation for early understanding of key processes in the brain (e.g. Broca’s and Wernicke’s area)
post-mortem studies improve medical knowledge and help generate hypotheses for further studies
weaknesses of post-mortem
causation- observed damage in the brain may not be linked to the deficits under review but to some unrelated trauma or decay (e.g. age and drugs) Issues with establishing cause and effect
ethical issues of consent from the patient before death- a patient may have a significant brain abnormality when alive and are therefore too unwell to give consent for their brains to be investigated
spatial resolution
smallest feature/meaurement that a scanner can detect
temporal resolution
how quickly the scanner can detect changes in brain activity