ways of studying the brain Flashcards
post mortem
used to establish underlying neurobiology of particular behaviour
when individual dies, researchers examine their brains to look for abnormalities that might explain behaviour not found in control individuals
e.g broca’s work with patient Tan who displayed speech problems when alive and was subsequently found to have a lesion in broca’s area
scanning techniques - functional magnetic resonance imaging (fMRI)
technique for measuring changes in brain activity while person performs a task by measuring blood flow in particular areas of the brain which indicates increased neural activity in those areas.
if particular area of brain becomes more active, there’s increased demand for oxygen in that area and brain responds to this demand by increasing blood flow, delivering oxygen in red blood cells. as a result of changes in blood flow, researchers are able to produce maps showing which areas of the brain are involved in a particular mental activity
scanning techniques - electroencephalogram (EEG)
measures electrical activity in the brain. electrodes placed on scalp detect small electrical charges resulting from the activity of brain cells.
EEG data can be used to detect various types of brain disorder or to diagnose other disorders that influence brain activity.
EEG readings of patients with epilepsy show spikes of electrical activity. EEG patterns in patients with brain disease and brain injury show overall slowing of electrical activity
scanning techniques - event-related potentials (ERPs)
very small voltage changes in the brain triggered by specific events or stimuli, such as cognitive processing of a specific stimulus
to establish a specific response to a target stimulus requires many presentations of the stimulus and these responses are then averaged together.
waves occurring within first 100 milliseconds after presentation of stimulus are ‘sensory’ ERPs - reflect initial response to physical characteristics of the stimulus
ERPs generated after first 100 milliseconds reflect how the subject evaluates the stimulus and are ‘cognitive’ ERPs as they demonstrate info processing
fMRI strengths
non invasive, nor does it expose brain to potentially harmful radiation
offers more objective and reliable measure of psychological processes than possible with verbal reports - useful as a way of investigating psychological phenomena that people wouldn’t be capable of providing in verbal reports
fMRI limitations
measures changes in blood flow in brain so isn’t direct measure of neural activity in particular areas of brain - not truly quantitative measure of mental activity in these areas
overlooks networked nature of brain activity as it focuses only on localised activity in brain - communication among different regions is more critical to mental function
EEG strengths
provides recording of brain’s activity in real time rather than a still image of the passive brain - researcher can accurately measure particular task or activity with brain activity associated with it
useful in clinical diagnosis, e.g by recording abnormal neural activity associated with epilepsy. epileptic seizures are caused by disturbed brain activity meaning the normal EEG reading suddenly changes - helps diagnose whether someone experiencing seizures has epilepsy
EEG limitations
EEG only detects activity in superficial regions of brain so cannot reveal what’s going on in deeper regions such as hypothalamus or hippocampus. electrodes can be implanted in non humans to achieve this, but it’s not ethically permissible to do this with humans as it’s too invasive
electrical activity can be picked up by several neighbouring electrodes so EEG signal isn’t useful for pinpointing exact source of activity - doesn’t allow researchers to distinguish between activities originating in different but closely adjacent locations in brain
ERP strengths
ERPs provide continuous measure of processing in response to particular stimulus, making it possible to determine how processing is affected by specific experimental manipulation
ERP can measure processing of stimuli even in absence of behaviour response. ERP recordings making it possible to monitor ‘covertly’ the processing of a particular stimulus without requiring person to respond to them
ERP limitations
ERPs are so small and difficult to pick out from other electrical activity in brain so it requires large number of trials to gain meaningful data - places limitations on types of question ERP readings can realistically answer
only sufficiently strong voltage changes generated across scalp are recordable. important electrical activities occurring deep in brain aren’t recorded, meaning the generation of ERPs tends to be restricted to the neocortex
post-mortem examinations strengths
post-mortem studies allow for more detailed examination of anatomical and neurochemical aspects of brain than would be possible with sole use of non-invasive scanning techniques like fMRI and EEG
harrison - post-mortem studies have played central part in understanding origins of schizophrenia. suggests that as direct result of post-mortem examinations, researchers discovered structural abnormalities of brain and found evidence of changes in neurotransmitter systems, both of which are associated with SZ
post-mortem examinations limitations
people die in variety of circumstances and at varying stages of disease which can influence post-mortem brain. similarly length of time between death and post-mortem, drug treatments and age of death are possible confounding influences of any difference between cases and controls
limited as it’s retrospective as person is already dead, as a result researcher is unable to follow up on anything that arises from post-mortem concerning possible relationship between brain abnormalities and cognitive functioning
