brain scans

Question 1

what are the two types of brain scan

Answer 1

• functional

- structural

Question 2

what are CAT scans

Answer 2

• use a series of x ray beams passed through the head to from cross sectional images of the brain - shows the structure but not the function
• produces slices through the head which can be looked at individually or put together into a 3D image
• formed by how areas of the brain react to the x rays being passed through them
• iodine or barium dye can be used

Question 3

process of CAT scans

Answer 3

• remove all jewellery
• lie on a scanner table
• keep still for 20-30 minutes
• staff leave room and continue to talk to you
• table moves through the scanner and rotates in small movement to take further pictures

Question 4

advantages of CAT scans

Answer 4

• quick and detailed results
• can accurately see brain layout
• reduces risk to patient
• can detect physical changes to brain
• used for academic research to treat patients
• not painful and non invasive

Question 5

disadvantages of CAT scans

Answer 5

• x rays can pose risk to individuals as exposure to radiation can be harmful
• MRI gives a clearer picture - better for looking for infection whereas CAT scans are better for looking at fractures
• can’t be routinely used as radiation could cause cancer

Question 6

what are PET scans

Answer 6

• scanner detects radioactive material that is injected or inhaled to produce an image of the brain
• once in the blood stream it flows through the brain and oxygen and glucose accumulates in the brain areas that are active
• as the glucose is used in the active parts of the brain, the radioactive material breaks down and gives off positrons
• positrons collide with electrons and form gamma rays that are picked up by the scanner
• provides a functional view of the brain
  carried out for medical purposes or in research
  can be compared with a ‘normal’ individual
  epilepsy and other conditions can be studied

Question 7

advantages of PET scans

Answer 7

• reasonably non invasive and no surgery
• valid as measures what it says it measures
• reliable as can be repeated and same results can be found

Question 8

disadvantages of PET scans

Answer 8

• use of radioactive tracer is invasive so there are ethical issues
• scan can be claustrophobic - must be carefully explained
• difficult to isolate different brain function precisely

Question 9

what is an fMRI scan

Answer 9

• head is placed inside a very powerful large electromagnet
• nuclei within hydrogen molecules in water align themselves with the direction of the field
• as neural activity increases in the brain, blood flow increases to keep up with the demand for O2
• the o2 is carried to the neurones in Hb within red blood cells
• Hb when carrying o2 repels magnetic fields
• when it is deoxygenated it will follow the magnetic field
  the machine detects these changes
  can be used to produce activation maps showing which parts of the brain are involved in a particular mental process
• head is placed in a brace and may have a mask over your face

Question 10

advantages of fMRI scans

Answer 10

• no danger from radiation, main type of scan chosen as there is no invasion, surgery or radiation
• detection of change in blood flow is very precise so even slight changes can be detected
• good for medical use

Question 11

disadvantages of fMRI scans

Answer 11

• fMRI cannot look at actual receptors of neurotransmitters but a PET scam can
• too much head movement can distort the image
• measures the brain activity at rest but brain is never fully at rest so not easy to get a baseline to measure
• risks such as those with pace makers and claustrophobia

Question 12

what did Dimoka find

Answer 12

the finings of the behavioural study about trust and distrust did relate to fMRI findings (prefrontal cortex) giving some validity

Question 13

how are brain scans used to investigate aggression

Answer 13

• RAINE = used PET scans to look at brain activity of prisoners convicted of murder and compared to a control group of non murderers
• MONTAG = used fMRI scans and found that games showed lower levels of activity in reaction to pictures of negative emotional stimuli and may explain why there is a suggested link between playing a lot of violent games and becoming more aggressive
• BETTS used CAT scanning to show he had damage to the brain that might have led to his aggression. scan showed some damage including widened sulci. used to show his actions weren’t thought through. 60-77% of pleading NGRI have a psychosis and 10% have a psychosis that is neurological based.
• MATTHIES = used MRI scanning to measure the volume of the amygdala and took an aggression score. they were tested for a relationship and significance correlation was found. the smaller the amygdala the higher the aggression.

Question 14

evaluation of using brain scans to explain aggression

Answer 14

• strong research has been done using meta-analysis (support one another)
• brain scanning is valid as it is measuring brain activity and structural issues
• cannot establish a baseline measurement
• Brunnlieb research