IB Docs (2) Team
SAQ marking: Brain imaging
Below you will find four sample SAQs for the question: Explain the use of one technique for studying the role of the brain in behaviour.
For each of the samples, refer to the rubric to award marks 1 - 9. After each sample, there is a predicted grade as well as feedback on the strengths and limitations of the sample.
SAQ rubricSAQ Sample 1
Before the advent of modern technology, psychologists had to rely on studying human behaviour through case studies of patients with brain damage or autopsies to understand the brain. In modern times neuro-imaging technology has allowed psychologists to look at a living participant's brain in a non-invasive way. One such example is the MRI (magnetic resonance imaging), which allows psychologists to look at the structure of the brain. By applying a very strong magnetic field to the brain, the MRI causes the protein spins in hydrogen atoms to align to the magnetic field polarization. Hydrogen is present across the brain as so much of the brain is made of water. A static image is created through a compilation of many different snapshots of the brain. It is possible to create either a 2D slice or a 3D model of the brain. This image gives an indication of the structure of the brain, but it does not provide any indication of function.
Maguire did a study that used an MRI to look at neural plasticity and localization of function in the brain. To do this she looked at MRI scans of right-handed male taxi drivers who had been driving for at least 1.5 years. She then compared them to right-handed males who were not taxi drivers. She found that the taxi drivers had larger posterior hippocampi than non-taxi drivers, but that they also had smaller anterior hippocampi. The fact that only certain areas of the brain were impacted by being a taxi driver supported the theory of localization of function. She postulated that the posterior hippocampus must play role in spatial memory. She also found through voxel-based morphology which measures the volume of the brain from the MRI scans that more grey matter in the hippocampus correlated with the number of years as a taxi driver. This supported the theory of neuroplasticity, as the brain appeared to change as a response to external stimuli.
Maguire’s study shows how imaging techniques such as the MRI can be used to study the brain. One limitation of the study is that because no independent variable was manipulated, the findings are only correlational. We cannot assume causality. However, the MRI allowed Maguire to look at this structure of the participants’ brains in a noninvasive and ethical way.
364 words
SAQ Sample 2
One technique used to study the brain is case studies. Case studies are natural experiments in which some variable has naturally occurred – in this case, in the brain. This technique is very rare, as it requires that the participants have brain damage that is natural in order for the experiment to be ethical. One study that uses this technique is Milner’s study of HM.
HM suffered from a severe head injury in his childhood. At the age of 10, he began to have epileptic seizures. He underwent surgery at the age of 27 in order to cure his epilepsy. Tissue from his medial temporal lobe, as well as his hippocampus, was removed. It cured his epilepsy; however, he developed retrograde and anterograde amnesia. Milner studied his brain and concluded that due to the damage done to the hippocampus, he was unable to create a new episodic memory or semantic knowledge. She knew this by carrying out extensive testing - for example, IQ testing and memory tests, as well as an MRI. However, he was still able to learn procedural memories.
The experiment was conducted after the surgery meaning that all the variables were caused by the surgery and were not manipulated by the researcher. This means that HM did not experience any undue stress or harm. The experiment was also longitudinal which is how many case studies are done to study the brain.
220 words
SAQ Sample 3
One technique used to study the role of the brain in behaviour is an fMRI. The aim of Sharot's study was to study the role of the limbic system in flashbulb memories. In order to carry out her study, she had participants lie in an fMRI. The participants had all experienced 911 and felt that they had strong memories of the event. When they were in the fMRI, she flashed words in front of them. The words were matched either with the word "September" or with the word "Summer." The participants were told to think of a summer holiday or to think of 911. While they were in the fMRI, their brain activity was observed. The fMRI shows which parts of the brain are functioning at any one time. When the participants saw images linked to their summer holidays, the parahippocampus was activated. When 911 was flashed, the amygdala was activated. This study shows that the amygdala plays a key role in flashbulb memories.
164 words
SAQ Sample 4
One technique used in studying the brain is an autopsy. When psychology was still young, autopsies were used to study the brain because it was not possible to study the brain in a non-invasive way. For example, in the case of Broca's Tan. However, even with modern technology, autopsies are still used in order to get a better understanding of how the brain works. When a brain is obtained, it is frozen and then sliced so that powerful microscopes can be used to see more exact detail about the nature of the brain than can be detected on MRIs.
One study was done by LeVay on the brains of homosexual men. His goal was to see if there were any differences between "gay" and "straight" brains. He obtained the brains of 20 gay men who died of HIV in the US and 16 straight men who had died either of AIDS or something else. The brains were frozen, sliced and then stained in order to measure the size of the nuclei in the hypothalamus. The study was a blind study, so the researchers did not know which brain tissue samples belonged to gay vs straight men. The findings were that the INAH3 nucleus of the hypothalamus was larger in the gay men than in the straight men.
Autopsies are problematic because they are invasive. In addition, it is difficult to get consent in order to carry them out. However, in LeVay's study, there would have been no other way to do the research at that time in history.
260 words
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