methods: brain-scanning techniques Flashcards
1
Q
what does CAT stand for?
A
- Comouterised Axial Tomography
2
Q
what can CAT scans be used for?
A
- to take images of any part of the body including the brain
3
Q
what do CAT scans of the brain involve?
A
- it involves x-rays into the **head*
- unlike a standard x-ray where the beam is focus on one specific area, multiple beams are passed around the head from different angles to gather more info
4
Q
what can standard CAT scans be used for?
A
- to investigate whether a bone is broken so a single beam focus on one area would be useful
- when scanning something as complex as the brain, more info will be needed
5
Q
how is info from multiple x-ray beams interpreted? (CAT)
A
- by a computer
- detailed image of structure of brain can be seen
6
Q
what are the advantages of cat scans? (CA)
A
- having detailed image of the brain by computer is useful for detecting areas of brain damage following accident or positioning of tumours in brain. however, it doesn’t give any info about how brain functions
- if scan removes need for exploratory surgery then this would be preferable, especially as unnecessarily having brain surgery could be more risky for patient
- very quick to conduct and can give accurate details of brain structure, which helps guide clinicians in decision making regarding treatment or surgery
- may help surgeon to better plan a procedure before surgery takes place by being able to accurately see layout of brain structures before physically entering the skull
- may make procedure faster and more efficient, reducing risks associated with longer duration under anaesthetic for patients
7
Q
what are the disadvantages of CAT scans?
A
- use of x-rays can pose risk to patients as they involve exposure to radiation
- it’s advised that x-rays are only used whether the possible benefits in relation to diagnosis outweighs the potential risks
- pregnant women are advised to not have CAT scans wherever possible as there’s some evidence that exposure to x-rays can cause damage to unborn baby
8
Q
what does PET scans stand for?
A
- Positron Emission Tomography
9
Q
what are PET scans?
A
- form of nuclear medicine procedure as they involve injecting patient with small amount of radioactive material in order to conduct scan
10
Q
what are people having PET scans of the brain injected with?
A
- they’ll be injected with a substance known as ’fluorodeoxyglucose’ (FDG)
- this is a tracer substance where the radioactive atom is attached to glucose because brain will use up the glucose as a form of energy
11
Q
what happens after the tracer is injected? (PET)
A
- tracer will be absorbed into bloodstream
- after that, a task may be given to stimulate the brain (eg task used in Raine et al. study) and encourage activity
12
Q
what happens when activities stimulate the brain? (PET)
A
- brain starts working
- glucose will be used up and as this happens, radioactive atoms start to break down emitting positrons
13
Q
what happens in the process of breaking down emitting positrons? (PET)
A
- gamma rays are produced and it’s these that scanner picks up
- high concentration of gamma rays will be found in areas of high activity as a lot of glucose will have been up there, while areas of low activity will have fewer gamma rays present
14
Q
what are the images produced with the amount of gamma rays? (PET)
A
- in colour
- areas of high activity shown by warmer colours such as red
- areas of low activity shown by cooler colours such as **blue
15
Q
what are the advantages of PET scans?
A
- can be usefuk for investigating areas of the brain that are not functioning normally, which could indicate damage or tumours
- can detect areas of damage by indicating which parts of brain are showing abnormal levels of activity, which helps researchers to not only see where problems exist, but also predict what kind of issues patients might face in relation to brain activity being shown
16
Q
what are the disadvantages of PET scans?
A
- more invasive than other techniques eg CAT scans because they require patient to be injected with radioactive substance
- although this carries low risk due to very low levels of substance involved, it’s not advisable for patients to have too many of this type of scan unless absolutely necessary because it’s unclear whether there may be long term effects
17
Q
what does fMRI stand for?
A
- Functional Magnetic Resonance Imaging
18
Q
what are fMRI scans?
A
- relatively new procedure designed in 1990s
- to **enable images of brain activity* to be gathered without use of radiation
19
Q
what is the idea behind fMRI scanning?
A
- brain activity is associated with blood flow in the brain
- this activity is used to gather info by the scanner to produce a picture
20
Q
what is said about fMRI scanning due to its safety?
A
- because of its **comparative safety&* in relation to other forms of functional scans eg PET scans (which use radiation), fMRI scans are often procedure of choice for psychologists researching brain activity
21
Q
what does a fMRI scan involve? (1)
A
- having your head placed inside a very large and powerful electromagnet
- inside the magnetic field, the nuclei within hydrogen molecules in water align themselves with the direction of the magnetic field
22
Q
what happens when the neural activity increases in the brain? (fMRI 2)
A
- blood flow increases in the active areas to keep up with the demand for oxygen
- oxygen is carried to the neurons in haemoglobim within red blood cells
- haemoglobin, when carrying oxygen, repels a magnetic field (diamagnetic), but when it’s been deoxygenated it will follow direction of the magnetic field (paramagnetic)
- it’s these changes that the scanner with detect to create an image
23
Q
where does the scanner send info to? what happens next? (fMRI)
A
- scanner sends info to computer that’s then able to create a map of activation to show changing levels of neural activity in different brain areas as tasks are being completed
24
Q
what are the advantages of fMRI scans?
A
- scans are non-invasive and don’t involve any injections of radioactive substances so they don’t have any of the potential risks associated with PET scanning
25
Q
what are the disadvantages of fMRI scans?
A
- because of high-powered magnetic fields in scanning, some people are unable to have these kind of brain scans. eg anyone with cardiac pacemaker or who’s had recent metal surgical implants wouldn’t be able to have one of these scans
- anyone’s who’s claustrophobic or unnerved by confined places or loud noises may become quite stressed during scan procedures as they have to lie flat and still in a large tube for duration of scan. this can upset some people and therefore may not be suitable for all patients
26
Q
what have psychologists been doing in recent years?
A
- using brain scanning methods to make links between brain structures and activity, and variety of human behaviours
27
Q
what is an element of human behaviour that psychologists are interested in?
A
- aggression
- researchers have been using different scanning techniques to exp,win aggressive behaviour
28
Q
research conducted by Raine et al
A
- researchers used PET scans to look at brain activity of prisoners convicted of murder and then compared this to matched control group of non-murderers
- using PET scans they were able to map abnormal brain activity in murderers’ group in areas of brain associated with impulsivity and risk-taking behaviour, which may explain increased aggressive behaviour
29
Q
research conducted by Montag et al
A
- research into violent video games has investigated how brains of gamers process emotions to see if playing these games may change brain activity, making people more likely to become aggressive
- used fMRI scans and found that gamers showed lower levels of activity in reaction to pictures of negative emotion than control group
- this dampening of brain’s response to negative emotional stimuli may explain why there’s a suggested link between playing a lot of games and becoming more aggressive, as gamers may not find aggressive actions as ‘serious’ because their brains don’t process them in that way
