Brain scans - Research method

Question 1

What are the 3 types of scans?

Answer 1

CAT, PET, fMRI

Question 2

How does a CAT scan work?

Answer 2

• Multiple beams of x-rays are passed around brain from different angles
• Gives a grey-scale image
• Sometimes inject a dye to make certain features stand out

Question 3

Give an example of how CAT scans were used in bio psych:

Answer 3

Betts (2009) - Case of Herbert Weinstein

Defence was CAT scanning showed he had brain damage, which may have led to his aggression (strangling his wife)

Question 4

What are the strengths of CAT scanning?

Answer 4

• Faster + cheaper than PET or fMRI
• Non-invasive (usually)
• Can image bone, soft-tissue, blood vessels, unlike PET or fMRI

Question 5

What are the weaknesses of CAT scans?

Answer 5

• Doesnt show info about brain function/activity
• Potentially harmful due to radiation exposure

Question 6

How does a PET scan work? (explain injecting part - 1st bit)

Answer 6

• Inject patient with small amount of radioactive material (FDG)
• Tracer substance is attached to glucose
• Once absorbed, task to encourage brain activity may be given. Glucose used up in active parts of brain
• Brain uses glucose up (glucose metabolism) + radioactive atoms start to break down, emitting positrons
• High glucose metabolism = High brain activity

Question 7

How does a PET scan work? (Explain gamma rays - 2nd part)

Answer 7

• This produces gamma rays which scanner picks up
• High concs of gamma rays means high area of brain activity + vice versa
• High activity shown by warmer colours + low activity shown by cooler colours

Question 8

Give an example from bio psych where PET scans were used:

Answer 8

Raine et al (1997) - Used PET scans to investigate differences in the brains of murderers + non murderers

Question 9

What are the strengths of PET scans?

Answer 9

Has ability to investigate brain activity - Useful as brain activity can be compared between ppl doing diff types of tasks

Indicates which areas of brain are responsible for diff functions

Question 10

What are the weaknesses of PET scans?

Answer 10

• Pics are less detailed
• Most invasive

Question 11

How does an fMRI scan work? (1st part - magnets)

Answer 11

• Head placed in very large, powerful electromagnet + patient engages in task
• Inside magnetic field, nuclei within hydrogen molecules in water align with magnetic field - this is passed around head

Question 12

How does an fMRI scan work? (2nd part - brain activity)

Answer 12

• As brain activity increases, blood flow increases to ensure supply of O2
• Haemoglobin carries O2 to neurons in brain (oxygenated haemoglobin repels mag field)
• O2 then supplied to neurons in brain + so haemoglobin becomes deoxygenated (this follows mag field)
• This is how image is generated

Question 13

Give an example where fMRI scans were used in bio psych:

Answer 13

Weber et al (2006) - Used magnets to scan brain + 13 male ppts played violent game to show whether violent games impact aggression

Question 14

What are the strengths of fMRI scans?

Answer 14

• Cheaper than PET scans but more expensive than CAT scans
• Non-invasive, doesnt involve injection
• Clear images

Question 15

What are the weaknesses of fMRI scans?

Answer 15

• Slower than CAT scans
• Lower temporal resolution than PET scans
• People with pacemakers or metal implants cant have these scans
• Sensitive to movement - voxel size low