Specification
- Brain-scanning techniques (CAT, PET, and fMRI). The use of brain-scanning techniques to investigate human behaviour, including aggression.
CAT Scans
A CAT scan (computed tomography) scan can be used to scan the brain and produce detailed images of its structure and function. A CT scan of the brain is also known as a head CT scan.
During the procedure, the patient lies on a table that is slid into the CT scanner. The patient is typically asked to hold still and keep the head in a specific position, as the X-ray source and detector rotate around the head. The scanner captures multiple images of the brain from different angles, which are then sent to a computer.
The computer uses the information to create detailed cross-sectional images of the brain. These images can reveal the presence of tumors, blood clots, and other abnormalities. CT scans can also be used to identify damage from head injuries, strokes, and other conditions.
A CT scan of the brain can also be done with contrast, which is a special dye that is injected into the patient’s bloodstream before the scan. The dye helps to highlight certain structures in the brain, such as blood vessels, tumors, or infection.
Evaluation
- CAT scans are widely available and do not require specialised equipment, which makes it a convenient method of imaging the brain.
- CAT scans give objective data as the computer forms an image from the scan, so increasing the reliability of the results from the CAT scan as the results are not subjective.
- CAT scans emit radiation which means they can be harmful to some people, therefore they may cause harm to some people such as the foetus if a woman does not know she is pregnant.
PET Scans
A PET scan can be used to scan the brain and produce detailed images of its function and activity. During the procedure, the patient is injected with a small amount of a radioactive substance, called a tracer, which is typically a form of glucose (FDG). This tracer will emit positrons that will collide with electrons in the brain tissue, and when the collision occur, gamma rays are emitted. These gamma rays are detected by the PET scanner, which creates detailed images of the brain’s activity and function.
The tracer is taken up by cells that are active and consuming glucose, and the PET scanner will detect the gamma rays and create an image of the active brain areas. This allows the doctors to identify areas of the brain that are not functioning properly, such as in cases of Alzheimer’s disease, brain tumours, and other neurological disorders.
PET scans can also be combined with a CT scan, which provides detailed images of the brain’s structure, to create a more detailed picture of the brain and its function.
Evaluation
- PET scans are not widely available and it can be expensive.
- PET scans are not used on children or pregnant women and are therefore unable to measure the relationship between biological factors and behaviour in these groups which is a slight limitation of this technique.
- PET scans can not be used on everyone, and some people are allergic to the radioactive tracer.
fMRI Scan
An fMRI (functional magnetic resonance imaging) scan is a type of medical imaging that is used to produce detailed images of the brain’s activity and function. It works by measuring changes in blood flow and oxygenation in the brain, which can indicate which areas of the brain are active and working.
During an fMRI scan, the patient lies on a table that is slid into a large cylindrical machine, called a scanner. The scanner uses a strong magnetic field and radio waves to produce detailed images of the brain’s structure. As the patient lies in the scanner, they will be asked to perform a specific task, such as looking at pictures or solving math problems, while the scanner captures images of the brain.
The scanner detects changes in blood flow and oxygenation, which occur when an area of the brain is active. The scanner then creates detailed images of the brain’s activity, which can be used to identify areas of the brain that are not functioning properly, such as in cases of stroke, brain injury, or neurological disorders like Alzheimer’s disease or PTSD.
Evaluation
- An advantage of fMRI is that is non-invasive. Unlike other scanning techniques, for example Positron Emission Tomography (PET), fMRI does not use radiation or involve inserting instruments directly into the brain, and is therefore virtually risk-free. Consequently, this should allow more patients/participants to undertake fMRI scans which could help psychologists to gather further data on the functioning human brain and therefore develop our understanding of localisation of function.
- fMRI scans have good spatial resolution. Spatial resolution refers to the smallest feature (or measurement) that a scanner can detect, and is an important feature of brain scanning techniques. Greater spatial resolution allows psychologists to discriminate between different brain regions with greater accuracy.
- fMRI scans do not provide a direct measure of neural activity. fMRI scans simply measure changes in blood flow and therefore it is impossible to infer causation (at a neural level). While any change in blood flow may indicate activity within a certain brain area, psychologists are unable to conclude whether this brain region is associated with a particular function.
- fMRI scans are safer than PET scans as they do not use radiation, so maybe more useful for researching human behaviour.
- However, it is relatively expensive and the results can be influenced by factors such as head movement, susceptibility artefacts and the presence of metal in the body.
Past Paper Questions
2 Markers
- Explain one strength of Jayla using a PET scan in her research. (2) June 2017
- Describe how a CAT scan is used in biological psychology. (2) October 2018
4 Markers
- Explain two ways Jayla could have improved her study. (4) June 2017
- Explain one strength and one weakness of the use of CAT scans in biological psychology. (4) October 2018
8 Marker
- Evaluate the use of brain-scanning techniques in biological psychology. (8) January 2022
16 Marker
- Evaluate the use of fMRI scans and the observational research method to research human behaviour. (16) October 2019