Other biological research methods

Question 1

What is a CAT (Computer tomography) scan?

Answer 1

Uses X-rays and a computer to create detailed struvtural images of the inside of the body, including the brain.
The person lies inside a large doughnut shaped scanner and the scanner is slowly rotated around them. Images of the brain (or body) are taken from different angles
Each image is cross section of the person’s brain (or body). When all the “slices” are put together this can build up a very detailed picture

Question 2

What are some positives about CAT scans?

Answer 2

• Are useful in revealing abnormal structures in the brain such as tumours or structural damage. The quanlity of the images provided by the CAT scan is much higher than that of traditional X- rays.

Question 3

What are some negatives of CAT scans?

Answer 3

• More radiation than traditional X- rays, and the more detailed and complex the CAT scan is, the more radiation exposure the patient receives. This means that CAT scans cannot be used often
• CAT scans only provide structural information. Unlike other scans, such as PET scans, they do not give information about activity of the “live” brain, they just produce still images. This means they have limied use in research linking brain areas to particular behaviours.

Question 4

What is a PET (positron emission tomogprahy) scan?

Answer 4

Measures the metabolic activity in the brain, i.e. the areas that are most actice.
A person is injected with a small about of radioactive substance such as glucose (the radiotracer). Brain areas that are most active will use more of it and this can be betected by the scanner.
This information is sent to a computer. The most actice areas are coloured red or yellow and the least active areas are represented as blue

Question 5

What are some positives of PET scans?

Answer 5

• PET scans show the brain in action, which is useful for psychological research. For example, Volkow used PET scans to correlate the activity of dopamine transporters during a cocaine induced “high” to a ppt subjective experience of the drug. This means that biological activity could be linked to behaviour (the ppts experience).
• PET scans indicate the specific areas of the brain that are involved in experience i.e they provide evidence of localisation of function. For example, the person can be asked to look at a picture, solve a jigsaw puzzle, or think about a memory in childhood and the linked brain area can be identified

Question 6

What are some negatives of PET scans?

Answer 6

• Sometimes the results are not easy to interpret. For example, PET scans on people doing the same task have shown different brain activity in different people. This makes it difficult to draw conclusions about which brain areas are linked to which behaviours
• The precise location of active areas in relation to brain structure is difficult to pinpoint
• There are ethical issues to do with the injection of radioactive glucose as used in PET scans. Radioactive substances cause damage to the tissues of the body, they may kill cells or cause mutations in the DNA cods in cells. This means the technique can only be carried out once every 6 months with any one individual and some people may refuse to participate. This further limits the use of PET scans for psychological research

Question 7

What is a fMRI (funnctional magnetic resonance imaging) scan?

Answer 7

Uses radio waves to measure blood oxygen levels in the brain
Those areas of the brain that are most active use most oxygen and therefore blood is directed to the active area. This is a haemodynamic response.
This activity/ response us picked up through radio signals and these signals produce a series of images of successive “slices” which are then turned into a 3D image by a computer

Question 8

What are some positives of an fMRI scan?

Answer 8

• As with PET scans, fMRI shows important information about which areas of the brain are being used at any one time. For example, Pardini used fMRI brain scans to measure the volume of ppts’ amygdalas and relate this to observed levels of aggression
• Unlike PET and CAT scanning, fMRI does not use radiation and so it is very safe method of studying the brain
• The images produced by fMRI are extremely clear and can show brain activity to the millimetre.

Question 9

What are some negatives of fMRI scans?

Answer 9

• Liek PET scans, fMRI is expensive to use
• The technique is only effective if the person whose brain is being investigated stays perfectly still and this may be a problem for some people, such as children. This limits the use of FMRI with some kinds of research
• There is around a 5 second time lag between the brain activity and the image appearing on the screen. This can cause probelms when trying to interpret the information received

Question 10

How did Lit et al us fMRI scans?

Answer 10

Used to investigate how heroin effects different parts of the brain. They found in the cue indured task activation of the PCF and other brain regions in the heroin group comparted to the control.

Question 11

How did Betts use CAT scans?

Answer 11

Discussed the case of Herbert Weinstein, CAT scan showed that he had damage to the brain which might have caused his aggression (strangled his wife). NGRI