The use of brain scanning techniques to investigate behaviour Flashcards
Examples of non invasive methods?
PET, CAT and fMRI scans
How do Computerised Axial Tomography scans work?
> uses x ray beams passed through the head from different angles, creating cross sectional images so showing brain structure but not function
if there is damage, observe behaviour
What is involved in the procedure of a CAT scan?
> all jewellery, glasses, metel removed, injection of dye to expose blood vessels
(20-30 mins) must keep still, painless
staff leave room, scanner table moves through scanner and takes pictures while rotating around your head
What does Positron Emission Tomography do?
Doughnut shaped scanner put around the head, shows activity of which parts are most/least active from different colours, warm = more activity, uses glucose and water
What is involved in the procedure of PET?
> Tracers injected into the bloodstream, brain takes up oxygen in the water/glucose and tracer decays
Tracer takes 10-15mins to decay, releases radioactivity, most active areas leave most radiation
What is a tracer in PET?
Radioactive versions of chemicals used up in brain activity - glucose/water, reaches brain after 1 min, helps PET as active brain areas use most glucose leaving radiation
What are positrons in PET?
Positively charged particles, they give signals that are picked up by recordings, radioactivity in the form of gamma rays which are produced when positrons collide with electrons
Example of how PET works?
If studying blood flow to brain, when someone is talking blood flow will be greater in areas that are most active in order to be able to talk
Which scans are ethical and why?
PET, fMRI and CAT because they are non invasive
Why could PET scans be slightly invasive?
Injection of glucose tracer, can be distressing
Why are PET scans valid?
They measure what they claim to do, validity can be different to check when measuring cognitive functions but PET scans have reconfirmed previous findings
What is a weakness of PET scans?
Hard to pinpoint exact areas of the brain so even if PET scans are clear, they are only valid up to a point as it is hard to claim from a scan whih area is performing each function
A strength of PET?
movement does not ruin the scan
How long does PET take?
2 hours
How long do fMRIs take?
2 hours
Strengths of CAT scans?
quick and accurate deails of brain structure, non invasive and not painful, may removed need for exploratory surgery
Weaknesses of CAT scans?
Doesn’t show function unlike PET and fMRI, involves x rays so should be used sparingly due to radiation
What did Maguire et al (1997) find as an example of PET?
The hippocampus was active when the taxi drivers described routes from one location to another, associatied with spatial memory
How does fMRI work?
Brain activity associated with blood flow in the brain and this activity is used to gather the info by the scanner to produce a picture
What is the process of fMRI?
> Place head in electrmagnet
Magnetic field: nuclei within hydrogen molecules will align themselves with the direction of the magnetic field
Scanner sends the info to the compueter to create the map of activation
What happens in the magnetic field of fMRI?
> neural activity increases in the brain, blood flow increases in active areas to meet demand for oxygen
oxygen carried to the neurons in haemoglobimn within red bood cells
What happens when haemoglobin carries oxygen in fMRI?
Repels a magnetic field and when deoxygenated it will follow the same direction of the magnetic field and the canner will detec changes to create an image
What does the map of activation show in fMRI?
Changing levels of neural activity in different brain areas as tasks are being completed
Why is fMRI a more ethical method of investigation?
Takes images from outside the body
