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Biological Approach Methods Brain scanning techniques (CAT, PET, fMRI) The use of brain scanning to investigate aggression One twin study – Gottesman and Shields Homework check Research one brain scanning technique from CAT, PET or fMRI. Scanning techniques could be drawn out of a hat. Be ready to present to the class Learning objectives 1) To describe and evaluate three brain scanning techniques (CAT, PET and fMRI) and be able to teach the basics of these to others. 2) To investigate how brain scanning is used to investigate aggression. 3) To become aware of one twin study (G&S) and be able to learn the APRC and GRAVE the study. 4) To practice independent research and questioning skills. Links to Issues and Debates: • Practical issues in the design and implementation of research – e.g. issues in scanning and measuring the complexity of the brain. • Psychology as a science – e.g. synaptic transmission; brain scanning techniques. • An understanding of how psychological knowledge has developed over time – e.g. development of scanning techniques up to fMRI. • Issues of social control – e.g. using knowledge of brain function to control individuals. Computed Assisted Tomography Scan (CAT Scan) • CAT scans use a series of X-ray beams passed through the head, creating cross-sectional images of the brain showing the structure, but not the function. How it happens • • • • • • You need to remove all jewellery and glasses and all metal etc You will be asked to lie on a scanner table You must keep still during the procedure which takes about 20-30 minutes The staff leave the room and continue to talk to you through an intercom The scanner table then moves through the scanner to take the first picture and rotates in small movements around your head to take further pictures It is a painless procedure • You might need an injection or injections as part of the procedure. This will be discussed with you before your scan. • A dye is injected into the back of your hand or into the crook of your elbow and flows around your bloodstream to highlight the blood vessels in your brain or spine. • This helps to produce more detailed pictures. Positron Emission Tomography (PET) • A scanner detects radioactive material that is injected or inhaled to produce an image of the brain. • Once in the bloodstream, it flows through the brain and oxygen and glucose accumulate in brain areas that are metabolically active. • As the glucose is used in the active parts of the brain, the radioactive material breaks down and gives off a neutron and a positron. • When a positron hits an electron, both are destroyed and two gamma rays are released. • Gamma ray detectors record the brain area where the gamma rays are emitted. • This method provides a functional view of the brain. E.g. language involves a number of areas in the brain. By asking someone to think of words, read words, or speak words researchers can find out which part of the brain works for a particular language function. PET scans • They are mainly carried out for medical purposes, e.g. to check the damage made by a stroke • They can also be used to research how the brain works e.g. in individuals with schizophrenia • They can be compared with ‘normal’ individuals to learn more about the illness • Epilepsy and other conditions can be studied by looking at blood flow in the brain. Positron Emission Tomography (PET) Advantages • A reasonably non-invasive way of studding inside the brain (or body) – although the radioactive tracer is invasive • Ethical • Valid – the scan seems to measure what it claims to measure e.g. speech has been consistently found to be connected to Broca’s area • It is reliable – it can be repeated and the same results found – the same areas of the brain are consistently found for different activities Positron Emission Tomography (PET) Disadvantages • The use of the radioactive tracer is invasive so there are ethical issues – the researcher must follow ethical guidelines carefully (e.g. gained informed consent, having a good reason for doing the test. • The scan itself is claustrophobic – it must be carefully explained to the individual. • It is difficult to isolate different brain functioning precisely. E.g. people can read passages of text while being scanned but they would almost certainly be using other parts of their brain as well. It is valid to a point. • It is also expensive to use. Magnetic Resonance Imaging (MRI) • MRI uses detection of radio frequency signals produced by displaced radio waves in a magnetic field. It provides an anatomical view of the brain. • The whole body is placed inside a tube, which can be claustrophobic. • The process is noisy but not painful. MRI • MRI scans are affected by movement so the person has to keep very still. • MRI scans do not show activity to the same degree as PET scans, but they can measure blood flow. • Before an MRI scan, a dye called a contrast medium, is injected into the body to help show up body organs and relevant areas. Magnetic Resonance Imaging (MRI) Advantages • No X-rays or radioactive material is used. • Provides detailed view of the brain in different dimensions. • Safe, painless, non-invasive (apart from the injected dye). • No special preparation (except removal of all metal) is required from the patient. • It is valid because what is found in the scan is then often found in reality. They are accurate for checking abnormalities in the brain and the rest of the body. • More ethical – animals do not need to be used. • Replicable – it can be repeated and the same results found – the results can be checked by more than one person for objectivity. Magnetic Resonance Imaging (MRI) Disadvantages • MRI scans are stressful because an injection has to be given, they are extremely noisy and they can be claustrophobic. Stress should not be imposed on a patient without careful consideration of ethical guidelines and issues. • MRI scanning only measures particular things. There are for example clear images of soft tissue and body organs but brain activity is not measured. Knowledge from such scans is limited. Functional Magnetic Resonance Imaging (fMRI) • Functional magnetic resonance imaging, or FMRI, is a technique for measuring brain activity. • It works by detecting the changes in blood oxygenation and flow that occur in response to neural activity – when a brain area is more active it consumes more oxygen and to meet this increased demand blood flow increases to the active area. • FMRI can be used to produce activation maps showing which parts of the brain are involved in a particular mental process. • For fMRI, your head may be placed in a brace designed to help hold it still. This brace may include a mask that is created especially for you. You may be given special goggles and/or earphones to wear, so that audio-visual stimuli (for example, a projection from a computer screen or recorded sounds) may be administered during the scan. fMRI scans Advantages • • • • • It can noninvasively record brain signals without risks of radiation inherent in other scanning methods, such as CT or PET scans. It has high spatial resolution. 2– 3 mm is typical but resolution can be as good as 1mm. It can record signal from all regions of the brain, unlike EEG/MEG which are biased towards the cortical surface. fMRI is widely used and standard data-analysis approaches have been developed which allow researchers to compare results across labs. fMRI produces compelling images of brain "activation". Disadvantages • Dispute over whether or not it actual measures what it claims to measure – e.g. increased levels of oxygen could be in preparation for neural activity, not because of it. • Very noisy. (small signals and lots of ‘noise’ make it difficult to pick up changes in oxygenated blood flow. • The images produced must be interpreted carefully, since correlation does not imply causality, and brain processes are complex and often non-localized. • Statistical methods must be used carefully because they can produce false positives. Compare the three scanning techniques Issue Non-invasive Can scan brain activity Needs interpretation Scientific method Validity Reliability MRI scan PET scan fMRI scan Worksheet • Complete the work sheet to show you understand scanning techniques. • Answer the exam questions. How are brain scans used to investigate aggression? • What might brain scans show? • Which areas/structures of the brain are involved in aggression? • Which type/s of scans would this show on? Twin studies • What are twin studies? • How are they used in psychology? Stretch and challenge: Find about the TEDS study. Where is it taking place? Who are the participants? What do they hope to find? Using twin studies • One way of finding out whether a disorder has a genetic component is to see whether it runs in families. If relatives of sufferers have a higher than average risk of getting the disorder themselves, then it may be that the disorder has a genetic component. • However, family members typically share similar environments. Consequently, increased risk amongst close relative may simply indicate that that are exposed to the same set of environmental risks. • An alternative approach is to do a twin study. This looks at the concordance rate (degree of similarity) of twins with respect to the disorder being considered. Concordance rates means the probability of one twin having the disorder if the other already has it expressed as a percentage. • In a twin study, MZ (identical) and DZ (nonidentical) twins are compared. Whilst MZ twins have a greater degree of genetic similarity, both types of twin pair grow up in identical environments. • So if we discover that MZ twins have a higher concordance, this cannot be because their environments are more similar than those of DZ twins; it must therefore be because their genes are more similar. Gottesman and Shields • Read through the Gottesman and Shields twin study. • Make notes on the aim, procedure, results and conclusion of the study. • Complete the Sheet Describing and Evaluating the study. Gottesman and Shields (1966) 1) What was the aim of the study? 2) Who did they look at (who made up their sample)? 3) What types of twins did they study? 4) List two results. 5) List at least one conclusion they drew from their results. 6) What is a problem with this kind of research? 7) Why is this kind of research important? 8) How can it be applied today? Links to Issues and Debates: • Practical issues in the design and implementation of research – e.g. issues in scanning and measuring the complexity of the brain. • Psychology as a science – e.g. synaptic transmission; brain scanning techniques. • An understanding of how psychological knowledge has developed over time – e.g. development of scanning techniques up to fMRI. • Issues of social control – e.g. using knowledge of brain function to control individuals. Can you spot the links to Issues and Debates in today’s lesson? Homework ‘Flipped learning’ – • What are adoption studies? • Why are psychologists interested in them? • Pupils should also find and read the Adoption study by Ludeke et al (2012) • Pupils should come up with three positives about the study and three criticisms.