Brains Scans and Quasi Experiments Flashcards
why has it historically been difficult to look at the brain
- Historically you could only look at the brain post mortem
this is bad because: - can’t observe brain activity
- can’t see how it effects the individual’s behaviour
- can’t observe a healthy normal brain, like ours
what are the 4 types of scans you need to know
- EEG
- CAT
- MRI
- PET
what does each of the scans (EEG, CAT…) scan for + what do they stand for
- EEG (electroencephalogram) = brain function
- PET (Positron emission tomography) = brain function
- CAT (computed axial tomography) = brain structure
- MRI (magnetic resonance imaging) = brain structure
what is temporal resolution
describes its ability to tell you exactly when the activation happened
what is spatial resolution
Refers to the capacity a technique has to tell you exactly which area of the brain is active
how does an EEG work
- in 1950s it was the only method for studying brain activity
- electrodes placed on scalp will record the electrical activity in regions of the brain
how does a CAT scan work
- series of x-rays –> combining them to form an image (image is 2D but can also be 3D
- injecting a dye is sometimes used (helps highlights regions of the brain) –> creates a map of the brain’s structure
how does an MRI scan work
- patient is placed inside a large circular magnet
- causes the hydrogen atoms in the body to move
- when the magnet is turned off = these revert to their original positions
- producing an electromagnetic signal that is translated by a computer into pictures of brain tissue
how does a PET scan work
- patient injected with a radioactive tracker called FDG (fluorodeoxyglucose)
- after a period of time, patient is placed in a computer scanner
- positrons smash into electrons –> releasing gamma rays (which is picked up by the computer scanner)
- the detected emissions are plotted on varying levels of activity in the brain
- sometimes producing a 3D plot
why is using an MRI scan better than a CAT
- gives more detailed image of soft tissue in the brain (because it involves passing an extremely strong magnetic field through the patient rather than using x-rays
- best suited for when patient undergoes several examinations consecutively because it won’t expose the patient to hazards of radiations
why is using an MRI better than PET scans
- PET scans are less precise than MRI scans
- good when patient needs to go under examination several times = no injection required and no radiation exposure
why is using a PET scan better than CAT scans
- reveals chemical information = can distinguish between malignant or benign tumours
- can also show the brain in action = useful for psychological research
why is using a PET scan better than MRI
- reveals chemical information = can distinguish between malignant or benign tumours
- can also show the brain in action = useful for psychological research
why is using CAT scans better than MRI scans
- cheaper = so is more readily available
- it also takes less time
why is using CAT scans better than PET scans
- they provide structural information = can show tumours and structural damage in brain
what is the main advantages/disadvantages of a CAT scan
:)
- reveal abnormal structures in brain (e.g. tumours) , or structural damage
- the quality is much higher than traditional x-rays
:(
- requires more radiation than traditional x-rays, and the more detailed and complex the CAT scan is = the more radiation exposure the patient receives
- only reveals structural info
what is the main advantages/disadvantages of a MRI scan
:)
- more detailed imagery of the soft tissue in the brain than CAT scans do (due to passing a strong magnetic field through patient rather than using x-rays)
- very good for when patients need to undergo several examinations successively because (unlike CAT) it doesn’t expose the patient to hazards of radiation
:(
- MRI scans take along time and can be uncomfortable for patients
what is the main advantages/disadvantages of a PET scan
:)
- PET scans reveal chemical info that isn’t available with other imaging techniques (therefore able to distinguish between benign or malignant tumours)
- can also show brain action (useful in psychological research)
:(
- extremely costly technique –> not easily available for research
- the patient has to be injected with a radioactive substance
- the technique can only be used a few times once injected
- PET scans are les precise than MRI scans
what is a quasi experiment
an experiment where there is an IV but it has not been manipulated by the researcher.
–> THIS IS SEPERATE TO FIELD/LAB BECAUSE IN THESE, THE RESEARCHER WILL MANIPULATE THE IV
what are the 2 types of quasi experiments
- natural experiment
- Difference studies
what is a natural experiment
- A natural experiment is when it isn’t possible, practical or ethical to manipulate the IV. Usually this is because the IV has already been manipulated
what is a difference studies
- The IV is also naturally occurring, that it hasn’t been manipulated to vary by anyone, it simply exists. For example, it isn’t possible to manipulate the variable
what is the strengths/weaknesses of quasi experiments
:)
- allows researcher to investigate ‘real’ problems such as the effects of a disaster on health
- allows research where IV can’t be manipulated for practical or ethical reasons so a range of behaviours can be investigated
:(
- can’t determine causal relationships because the IV isn’t directly manipulated so we cannot be sure the IV caused the DV
- Threat to internal validity as there is less control over extraneous variables which may affect the DV
