Methods in Biological and Cognitive Psychology Flashcards
how have psychologists made inferences about localisations of brain functions in living humans
Behavioural evidence
Lesion studies
high spatial resolution imaging techniques (PET or MRI)
high temporal resolution imaging techniques
High spatial AND temporal resolution imaging techniques
brain stimulation techniques
Pharmacological interventions
direct electrophysiological techniques
Lesion studies
disassociation
brain damage = impairments in a particular domain of cognitive functioning
= association with damaged area and its function
double disassociation
Person A impaired in Task 1 not 2
Person B impaired in Task 2 not 1
= stronger evidence for dissociable/separate brain mechanisms
problems with lesion studies
patients are rare
damage is often not very circumscribed
“plasticity”
High spatial resolution brain mapping
PET
PET = Positron Emission Tomography
subject infused with radioisotope
radioactive decay used to measure cerebral blood flow - shows where brain activity is
technique has good spatial resolution
High spatial resolution brain mapping
MRI
Magnetic resonance imaging
function MRI : Blood Oxygenation Level Dependent (BOLD) imaging
How does fMRI work?
Neural firing triggers a change in the oxygenated blood flow to activate brain area (the haemodynammic response)
different magnetic susceptibility allows monitoring change in blood oxygenation levels
Deoxyhaemoglobin = paramagnetic ( attracts magnetic field) Oxyhaemoglobin = diamagnetic (repels magnetic field)
pros of High spatial resolution techniques
allows us to identify brain areas who’s activation in CORRELATED with particular types of operation
high temporal techniques
EEG/MEG activity - recorded as voltage or magnetic fluctuations close or on the scalp
reflects the summed effects of ionic current flow within bunch
neurons
What is EEG
Electroencephalography
recoded as a time series at multiple channels across the scalp
real time resolution of brain activity
poor spatial resolution due to spatial smearing
sources of EEG signal
results from combined activity of a large number of similarity oriented pyramidal neurons
required synchronous activity across groups of cells
reflects summed post synaptic activity of large cells ensembles
what is ERP
Event Related Potential
time locked averaging of segments of EEG from particular channels
index of the generic/ average brain response to a particular type of stimulus
inter cranial EEG
electrodes are place directly on the brains surface
What is MEG
Magnetocepholography
real time resolution of brain activity
Better spatial resolution than EEG
MEG signal soures
generated by the same process as EEG signals
BUT magnetic signature is tangential to the direction of the electrical current
difference between MEG and EEG
MEG is not distorted by intervening tissue between the generator and the sensor
meaning - signal inversion techniques are more effective for MEG
allows identification of brain regions generating the signal
Brain stimulation techniques
TMS
transreanial magnetic stimulation
focal magnetic pulses are used to disrupt brain functions in localised brain areas
