Brain scan essay

• A01 CAT scan pt 1

  Uses x-rays and a computer to create detailed  structural 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 a cross-section of the person’s brain or body. When all the ‘slices’ are put together this can build up a very detailed picture. Sometimes a dye is used to make the picture clearer, such as barium or iodine.
• A01 CAT scan pt 2

  The scan takes from a few minutes to 30 minutes. Pictures show how the area being scanned reacts to the x-ray, showing how far the x-ray is blocked, which could indicate a tumour or brain damage.In Psychology  CT scanning can be used to examine damage to the brain
• Cat strength A03 general

  • CAT Valuable in medicine to detect changes in physical structures to diagnose patients (i.e. good application) Is not painful and is non-invasive
• CAT scan strength in aggression A03

  • This is a strength because CAT scans can detect physical structures in the brain which might be damaged or such as tumours which might affect a person's behaviour such as aggression.
  • It is useful because using a CAT scan can help explain how brain damage of physical structures in the brain can affect aggression, can be used to screen people to see if they have underlying damage to their brain which could help decide on effective treatment programmes eg inmates in prisons.
• Cat weakness A03

  • CAT scans require 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  very often as receiving large amounts of radiation is harmful for the human body
  • CAT scans only provide structural information about bone, soft tissue and blood vessels but, unlike other scans, such as PET scans, it does not give information about activity of the ‘live’ brain, they just produce still images.
• CAT scan weakness relating to aggression A03

  • means CAT scans have a limited use in psychological research linking function of brain areas to particular behaviours compared to PET and fMRI, which both record brain activity, they cannot be used to determine the effect of activities on the brain in live tasks and can only to see physical structures.
  • CAT scans are useful for identifying areas of brain damage which could relate to aggression but cant be used to clarify function of brain areas in active tasks, less useful in understanding causes of aggression, which happen in real situations.
• PET A01

  Measures metabolic activity in brain through blood flow. Small amount of radioactive substance is injected in vein in arm. Brain areas which are most active will use more of it so be detected by the scanner. Info on the brain is sent to computer. Most active areas are coloured red/yellow, least are represented as blue. Allows researchers to work out what parts of the brain are working at what time. Tracer contains positrons; small positively charged particles. Can be used to measure blood flow in the brain. Can be used to map different types of neurotransmitter receptor in brain.
• PET strengths A03

  his is a strength because PET scans can indicate which specific areas of the brain are actively involved in behaviour, i.e. is useful for establishing which areas are localised for which functions. PET scans are useful because it can help researchers understand which parts of the brain are responsible for which functions in the brain.  It’s also useful because we can look at neurotransmitter receptors in the brain which other scans cannot detect.
• PET strength in aggression A03

  This is a strength, as it can enable researchers to study the action of neurotransmitters and how brain regions may be responsible for specific behaviours such as detecting threat, or responding aggressively.
• PET weakness A03

  The PET scan could be weaker due to the fact that it requires interpretations which could cause bias in the results of the scans

  Injecting the radioactive tracer is an invasive procedure and radiation can be harmful so there are ethical implications. It is difficult to isolate different brain functions specifically so we can’t be certain which part of the brain is performing which function (low validity)
• PET weakness in aggression A03

  This could effect the usefulness in investigating aggression as a false interpretation could be made and it could be difficult to determine aggression could actually be viewed in a pet scan 
• Fmri A01

  fMRI (Functional Magnetic Resonance Imaging) uses radio waves measuring blood oxygen levels in brain. When a certain area of brain is active, oxygenated blood is pulled to area which is associated with increases in neuronal activity (haemodynamic response).  Deoxygenated blood has magnetic properties (because oxygen neutralizes effect of iron in blood), ratio of oxygenated blood to deoxygenated blood is picked up as a signal by magnetic field of fMRI producing series of image slices, then converted into 3D image by computer, has high spatial resolution so scan is detailed
• Fmri strength A03

  There is no danger from radiation, and it is non-invasive, so it is the main type of scan chosen to use since the 1990’s. This is a strength because it will reduce the chance of mutations, e.g those that cause cancer, caused by radiation .

   

  Another strength is that detection of changes in blood flow is very precise so the scanning technique is very accurate which is excellent when used in medicine (or research). This is an advantage because it means that fMRI has finer spatial resolution than images from PET scans.
• fmri weakness A03

  If the patient moves it can distort the image and there is a time lag between the brain activity and the image appearing, which can cause problems when interpreting the scan. This is a weakness as it limits the use of fMRI with some kinds of research.

   

  Is unable to look at receptors of neurotransmitters, whereas a PET scan can do this, so it is not suitable for everything.

   

  There is around a 5 second time lag between the brain activity and the image appearing on screen. This can cause problems when trying to interpret the information received.
• CAT/CT scans give a grey-scale image showing a high level of detail of the structures of the brain. Unlike other types of scan, CAT/CT can image bone, soft tissue and blood vessels simultaneously. CAT/CT does not convey any information about brain activity or function. This limits its usefulness in psychology compared to PET and fMRI, both of which record brain activity.
• CAT/CT’s very detailed images can be useful to psychologists when trying to relate brain damage to changes in psychological functioning. CAT/CT is also faster and somewhat cheaper than PET and fMRI. Unlike PET it is non-invasive: usually, nothing enters the body, although sometimes a radiographer will inject a dye to make certain features stand out better. The X-rays used in CAT/CT are potentially harmful, but usually not in the dosage involved, although children should have their exposure limited.
• Its ability to investigate brain activity makes PET potentially very useful to psychologists as brain activity can be compared between people doing different types of mental task e.g. thinking of words versus doing mental arithmetic. This might indicate which brain areas are responsible for different mental processes.
• The pictures of brain structure produced by PET are less detailed than CAT or fMRI, and it is an invasive procedure. A higher dose of radiation is given than with CT/CAT, and the tracer remains in the body, although it decays quickly.
• fMRI measures blood flow to different parts of the brain and uses this to generate images of which brain areas are more active than others. This gives it many of the applications and strengths of PET scanning, particularly where it comes to understanding the role of different brain areas in different mental processes.
• fMRI has a finer spatial resolution than PET, so the images it produces are more detailed. fMRI is now the favoured technique by many researchers because it is non-invasive and there is no exposure to radiation. It is also cheaper and more practical in many cases because there is no requirement to prepare the radioactive tracers needed for a PET scan.
•  the blood flow response takes about two seconds, but a thought can happen in milliseconds. So it’s difficult to say that a rush of blood is associated with a specific activity in the brain. In addition, small movements by the participant can badly affect fMRI scans whereas PET scans are not so affected. Additionally, PET can be used to map different types of neurotransmitter receptor in the brain, whereas fMRI cannot so PET can be used to investigate a wider range of brain functions and behaviours than Fmri