3.2.3 - Brain Scanning

Question 1

CAT/CT - AO1

Answer 1

• CAT scans take slices of the brain using x-ray computed tomography and produces images in sections
• the pp lies on a platform for a few mins to 30 mins as a scanner moves around them as multiple beams are passed around the head from different angles.
• a dye can be used for highlighting purposes eg iodine to make the picture clearer for analysis
• slices can be looked at individually or put together to give a 3D view of the whole area
• the pictures are formed and pick up how the area being scanned reacts to the Xray passing through it showing how far areas block the x-ray; showing and used to understand brain damage and diff between individuals

Question 2

CAT/CT - AO3

Answer 2

• (-) A CT scan detects changes in physical structures accurately, especially as a 3D image can be used for diagnosis. However, fMRI and PET scans give better images and show the brain’s functioning, CAT scans are used more for medical purposes to check brain damage. → usefulness in biological psychology is very limited especially as x-rays expose the pp to more damaging radiation than traditional x-rays + so the more detailed and complex the scan is, the more radiation = only can be used infrequently
• (+) A CT scan is not painful or invasive (as long as no dye is used), its also quick to conduct and so may be more ethical than other scanning techniques → it may be more useful for pp who may suffer psychological harm or refuse to participate in other scans but who would be useful for research eg particular type of brain injury that would add insight into behaviours eg agg
• (-) CAT scans only provide structural information + unlike other types of scans eg PET, they don’t give detail on the activity of the ‘live’ brain and instead just produce images → they have limited use in linking brain areas to behaviours eg agg

Question 3

PET - AO1

Answer 3

• used to measure metabolic activity in the brain to see the areas that are most active
• a radioactive tracer is added to a chemical eg glucose that the body uses and is injected into a vein, usually in the arm
• tracer emits small positrons which give signals that are recorded. once the tracer is absorbed, into the bloodstream, a task may be given to stimulate the brain eg Raine
• as the glucose is used up in the brain, this shows up as an area of activity, more active the brain = more radioactivity picked up by scan
• recordings are displayed as images that can be interpreted = dark/warm - more activity

Question 4

PET - AO3

Answer 4

• (+) useful in biological research as they show us detailed images of the brain in action eg Volkow et al used PET scans to correlate the activity of dopamine transporters during a cocaine induced ‘high’ to a pps subjective experience of taking the drug → this is useful as it means that biological activity can be linked to behaviour to give a greater understanding of the topic
• (+) can indicate the specific areas of the brain that are involved in a particular behaviour eg Raine et al found that in the brain of murderers pleading NGRI, their agg behaviour did seem to come from diff in brain structures such as the amygdala which is associated with impulsivity, risk-taking and a lack of self-control.→ this is useful as it provides valid, visible results that are measurable and objective in providing a more detailed explanation of behaviours such as agg
• (-) However, although the activity shows up quite clearly on the image, it is difficult to isolate different brain functioning precisely e.g. Raine show that aggression uses many different parts of the brain and so it is difficult to claim which part of the brain is performing which function. Equally Raine suggested that a limitation was that the PET scan images were not particularly clear. Therefore results may not be measured clearly. They also fail to show the interrelationship between the brain and other factors causing particular behavior which limits their usefulness
• (-) there are also ethical issues to do with the injection of a radioactive tracer. This is invasive and also radioactive substances can cause damage to body tissue. Therefore, this limits the usefulness of this method as some participants may refuse to participate and for those who do, scans can’t be repeated regularly due to the potential of causing both psychological and physical harm

Question 5

fMRI - AO1

Answer 5

• fMRI builds on MRI scanning to look at functioning of the brain.
• the pps head is placed in a ver large, very powerful electromagnet
• inside the magnetic field the nuclei within hydrogen molecules in water aline themselves with the direction of the magnetic field
• as neutral activity increases in the brain, blood flow increases in the active areas to keep up with the demand for oxygen (oxygen is carried to the neurons in haemoglobin within RBC)
• haemoglobin, when carried in oxygen, repels a magnetic field but when deoxygenated it follows the direction of the magnetic field and its these changes that the scanner will detect to create an image eg Pardini et al measuring vol of pp amygdala and related this to lvls of agg

Question 6

fMRI - AO3

Answer 6

• (+) fMRI scans have validity because what is found in the scan is that often found in reality. E.g. Montag et al used fMRI scanning and found that gamers showed lower levels of activity in relation to pictures of negative emotion than the control group. Therefore this is useful in biological psychology as it gives us a greater understanding of behaviors. E.g. Montag et al were able to say that the dampening of the brain‘s response to negative emotional stimuli may explain why there is a suggested link between playing a lot of games And becoming more aggressive
• (+) can be more useful than other types of scans, such as pet scans, as they are relatively non-invasive and do not involve radiation and so are more ethical way to study the brain and the biological causes of behavior. Therefore they can be repeated more regularly and participants may be more willing to take part in research.
• (-)However fMRI scans can be unethical as they can be stressful as can require an injection of dye, are extremely noisy and can make people feel claustrophobic. Therefore invasive and could cause psych harm and unique pps who could help us understand behavior by looking at their brains may not want to participate
• (-) fMRI scans can’t measure the brain in a resting state so it has no baseline measures to set activity against, such as when someone is aggressive. Therefore they can’t establish cause and effect. E.g. it is unclear whether the differences in the brains of those that display high levels of aggression have been there from birth and also causing the aggression, or have developed in response to that aggressive behavior