L10- ways of studying brain Flashcards
brain studying techniques
- fMRI
-EEG
-ERP
-Post-mortems
fMRIs
- developed MRI
- neurons most active during an activity use more energy= requires glucose and oxygen carried in bloodstream= blood flow to active areas should increase over control levels= oxygen carried in bloodstream, attached to haemoglobin= released for active neurons, then haemoglobin deoxygenated
- fMRI indirectly measures blood flow through conc of oxygen in blood stream- BOLD contrast
- recent application- lie detector - hard to fake blood flow
- important for understanding brain localisation
strengths of fMRI
+ NON- INVASIVE -unlike PET, no radiation use, non-invasive= virtually risk free= allow more to undertake fMRI scans= further data on brain and localisation of function
+ GOOD SPATIAL RESOLUTION (1-2mm) (smallest feature scanner can detect)= discriminate between brain regions with greater accuracy then EEG/ERP
EEG
- Hans Berger 1929= overall view of brain activity
- lots of small recording electrodes (24-32) distributed over surface of skull= pick up electrical activity of millions of neurons
- has properties that can be used to characterise particular brain states through: - amplitude (intensity of electrical activity) + frequency (rapidity of electrical activity
-2 disticntive states of EEG - EEG data used to detect types of brain disorder or diagnose others that influence brain disease e.g eplilepsy, Alzheimers + different stages of sleep
2 distinctive states of EEG
- synchronised pattern- recognizable waveform can be identified
- desynchronised pattern- no recognizable waveform
different types of waves shown in EEG
- alpha ( awake)
-beta,
-delta (asleep) - thelta (asleep)
strength and weaknesses of EEG
+ recording of brain in REAL TIME rather than still image= accurately measure task
+ high temporal resolution,non-invasive
- only detect activity in superficial regions, cannot reveal activity in DEEPER regions
- low spatial resolution
disadvantages of fMRI
- CAUSATION= do not provide a direct measure of neural activity- only measure changes in blood flow= impossible to infer causation + fMRI scans only show localization of function in particular area of brain, limited in showing communication between areas- critical to neural functioning
- POOR TEMPORAL RESOLUTION (1-4s) ( accuracy of scanner in relation to time)= worse than EEG and ERP= unable to predict with high degree of accuracy the onset of brain activity
-COSTLY
ERPs
- very small voltage changes in brain triggered by specific events or stimuli
- similar array of recording electrodes like EEG, but stimulus is presented to participant and look for specific electrical response to that stimulus
- may be difficult to separate response to overall activity of brain = stimulus presented many times
- regular specific electrical responses to stimulus gradually add together while background electrical noise cancels itself out
eval of ERPs
+ SHORT LATENCY (interval between stimulus presentation and beginning of ERP) = can reflect vert early stages of cog. processing e.g. face processing and WM
+ high temporal resolution
- low spatial resolution, uncomfotable
- lack of standardisation in ERP methodolgy between diff research studies= findings cannot be confirmed= questions generalisability + EV must be minimised, not always posisble
Post- Mortem examinsation
- researcher may study brain while alive and suggest possible underlying brain damage- when dead researcher can compare brain to controls who don’t have abnormality, to look for abnormalities
- E.g- broca discovered lesion in Broca’s area
- Iverson examined brains of deceased schizos- higher conc of dopamine
- more detailed examination of anatomical and neurochemical aspects of brain + examine deeper regions of brain
eval of post- mortem
+ detailed examination of anatomical and neurochemical aspects, not possible through fMRIs and EEGs + deeper examination of hypothalamus, hippocampus
+ played central part in understanding origins of schizo- Iverson - high dopamine in limbic system
- individual differences= diff stages of disease and circumstances- confounding variables= length of time between death and autopsy, drugs, age of death = cannot make generalisations
- INVASIVE= but, not issue as dead= ethical issues= informed consent esp as most carried out on patients with psychological defects, unable to provide consent
