Brain scans

Question 1

How does a PET scan work?

Answer 1

• A radioactive chemical dye is injected into the blood of a person (irradiate glucose).
• As the chemical breaks down it releases radioactivity which can be picked up on the scan.
• The more active the brain for a specific task the more radioactivity that will be picked up by the scan.
• The scan creates a colourful image. Darker/warmer (red/orange) areas show more activity and lighter/cooler (blue/green) areas show less activity.

Question 2

What does a PET scan show?

Answer 2

Activity of the brain - which areas are using more glucose (energy)

Question 3

Give two strengths of a PET scan

Answer 3

Process is standardised

Objective measure of brain activity

Question 4

Give two weaknesses of a PET scan

Answer 4

Lacks ecological validity as it takes place in an artificial setting

Invasive as requires participant to be injected with a radioactive tracer

Question 5

How does an fMRI scan work?

Answer 5

• The person lies in a large cylinder in which they must lie perfectly still.
• Magnet and radio waves are then sent through the body.
• As neural activity increases in the brain, blood flow increases in active areas and requires more oxygen.
• Oxygen is carried to the areas via haemoglobin in red blood cells.
• Haemoglobin when it is full of oxygen repels the magnetic field (diamagnetic) but follows the field when it is deoxygenated (paramagnetic) and it uses these changes to build up an image.

Question 6

Give two strengths of an fMRI scan

Answer 6

Process is standardised so can be repeated

Objective measure of brain activity

Question 7

Give two weaknesses of an fMRI scan

Answer 7

Lacks ecological validity

Can be claustrophobic so some may not want to take part

Not accessible for everyone e.g. those with pacemakers cannot take part

Question 8

How does a CAT scan work?

Answer 8

• CAT scans involve a focused X-Ray beam being beamed into the brain.
• This is done at many angles which can then be put together into a full picture.

Question 9

What does a CAT scan show?

Answer 9

The structure of the brain

Question 10

Give two strengths of a CAT scan

Answer 10

Process is standardised

Objective measure of brain activity

Question 11

Give two weaknesses of a CAT scan

Answer 11

May be considered invasive due to frequent exposure to radiation

Lacks ecological validity