ways of studying the brain Flashcards
scanning techniques, including functional magnetic resonance imaging (fMRI); electroencephalogram (EEGs) and event-related potentials (ERPs); postmortem examinations.
spatial resolution
level of accuracy in identifying the exact location of a brain structure or brain activity in space
WHERE BRAIN ACTIVITY HAPPENED
temporal resolution
level of accuracy in identifying the exact location of a brain activity in time
WHEN BRAIN ACTIVITY HAPPENED
what the ways of studying the brain?
post-mortem dissection
fMRI
EEG
ERP
what is post-mortem dissection?
brains are precisely cut after treatment to give firmer texture
unusual brains are dissected e.g. brain suffered trauma, people with mental illness etc
these brains are compared with neurotypical brains
example of using post-mortem dissection
Broca used post-mortem dissection on Tan
found damage to area of the frontal lobe later known as Broca’s area
this dissection led to the discovery that Broca’s area is responsible for speech production
evaluations of post-mortem dissections
+ high spatial resolution allows the study of microscopic brain structures down to the neuronal level
- can only be conducted on dead brain so any damage found is correlational to unusual behaviour in life as it cannot be directly measured to find a causation
+ however, theories from post-mortems can be generated to be tested using more experimental techniques on living patients
+ these techniques have been significant in the historical development of psychology’s understanding of brain functioning such as the discovery of language centers e.g. Broca’s area
what is fMRI (functional magnetic resonance imaging)?
FMRI detects blood flow in the brain
more active areas in the brain need more blood which contains oxygenated haemoglobin with distinct magnetic properties so it appears on an FMRI image
active areas are compared to low activation areas with lower blood supply - this is what you can see on the fMRI image
evaluations of fMRI
+ high spatial resolution (~1mm) - precise in identifying active brain region and patterns of activation over time while participants complete experimental conditions
+ non-invasive and sage for experiments rather than PET scans which use radiation
- low temporal resolution as one image taken every few second and delay in blood flow after activity - some brain processes may be too fast to study
- fMRIs are expensive to build and operate
- PP must stay still so experiments involving body movements are not possible
what is the EEG (electroencephalogram)?
EEG device is a collection of 22-34 electrodes that attach to a cap fitted to the scalp with conductive gel
the read out from each electrode is the sum total of activation of the brain cortex under the electrode
this is displayed as a series of lines showing distinct patterns called brain waves
amplitude shows intensity of brain wave
frequency shows speed of activation
evaluations of EEG
+ non-invasive and non-surgical way to investigate living brain
+ historically important in understanding brain activity in sleep research and medical diagnosis
+ cheaper than FMRI
+ portable so can be used in situations which require participant to move
+ high temporal accuracy (~1 ms)
- poor spatial accuracy - cannot determine where brain activity is
- cannot detect activity deep within the brain only grey matter
- may be time-consuming process to attach electrodes
what is ERP?
ERP uses same technique and equipment as EEG but presents a stimulus many times, creating a smooth curve of activation by combing the data by statistical averaging to remove background electrical noise unrelated to stimulus
waveform’s peaks and dips show exactly when cognitive processes in the brain happen after the stimulus is presented
evaluations of ERP
+ allows researchers to isolate and study how individual cognitive processes take place in the brain (not general activity unlike EEG - more specific)
+ high temporal resolution
- low spatial resolution
- some processes cannot be studied by ERP as they cannot be presented a large number of times with the same response
way of combining brain studying techniques
some researchers have conducted studies combining the techniques of EEG and FMRI
comparing results of tasks performed with both in order to take advantage of the high temporal resolution of EEG and high spatial resolution of FMRI
