How to Answer a Discuss ERQ (DP IB Psychology)

Discuss the use of techniques used to study the brain in research into brain and behaviour [22 marks] 

Commentary

Techniques used to study the brain enable researchers to pinpoint with varying degrees of accuracy the structure, function or activity of the brain. Techniques include PET and MRI. Brain imaging technology is used in psychological research to provide biological correlates of behaviour (e.g., the prefrontal cortex and impulse control). Once a biological correlate for behaviour has been established then it is arguably easier for researchers to understand the reasons behind specific behaviours. Such research, however, does not provide a full explanation of all possible influences on the behaviour in question.

Raine (1997) investigated the role of the prefrontal cortex (PFC) in impulsive behaviour. The PFC is thought to regulate executive functioning, as seen in activities such as planning, reasoning, impulse control. Raine was interested in trying to establish a link between impulsive murder and a lack of PFC activity. Using a PET scan to investigate this possible relationship enabled Raine to establish which areas of the brain were active during a cognitive task. PET scanning involves the injection of a radioactive tracer into the participant; which appears as a bright colour on the brain scan, indicating which areas of the brain are most active in metabolising glucose during the task. The brighter the colour, the more active that part of the brain is during that particular task.

The sample Raine obtained consisted of 41 murderers who had pleaded NGRI (not guilty by reason of insanity) and 41 age and sex-matched controls. NGRI participants were used to attempt to find a relationship between their type of impulsive crime and a lack of ‘normal’ brain functioning. One issue that could, however, compromise the results was the fact that the control group were not murderers which might compromise the results as Raine did not compare impulsive murderers with premeditated murderers which might have yielded more useful data in terms of the types of crimes committed with links to brain function.

What Raine found after conducting the PET scan (during which the participants completed a continuous performance cognitive task) was that the NGRI participants had lower glucose metabolism in their PFC than the controls, plus asymmetry in the activity of the amygdala (linked to emotional responses). Raine concluded that NGRI murderers do not use their PFC to interpret and respond to non-emotional stimuli; they may use their amygdala instead. The NGRI participants are likely to have exercised low impulse control when they committed their crimes. The external validity of such a finding is, however, debatable; it is not a straightforward path from a PET scan image to behaviour enacted in real settings. Other explanations for their crime could be non-biological e.g., alcohol abuse, situational pressure, upbringing in a violent home etc. In this way, a PET scan is limited as it can only tell one part of a complex story.

Another brain-imaging technique is MRI, in which a powerful magnetic field is placed around the brain. It temporarily holds the nuclei of the brain's atoms in one direction. When released, the atoms "wobble" back to their original positions and emit a weak radio frequency signal that can be picked up by a sensitive receiving device. One advantage of MRI compared to PET is its non-invasive character: the MRI does not involve an injection. A drawback with using MRI, however, is that the image can take several minutes to form, so patients have to remain completely still which may cause problems if the patient is a child or suffers from claustrophobia.

Maguire et al. (2000) used MRI scans to compare the volume of grey matter in the brain of London taxi drivers compared to a pre-existing sample of matched controls (matched for gender, age and handedness). Maguire was interested in examining the hippocampi of both samples as she had hypothesised that taxi drivers would show significantly higher volumes of grey matter in their hippocampi: a structure in the brain associated with navigational skills. By using an MRI scan Maguire was able to ascertain specific differences in the taxi drivers compared to the controls. She applied two methods of analysing the scans: voxel-based morphometry (VBM) and pixel counting. VBM involves scanning the whole brain and then normalising the image using a template which sorts the information into either grey or white matter.

The pixel counting analysis of the MRI scans was achieved via a blind observer counting the pixels (a two-dimensional area measurement) in the scan images. Using a blind observer could be said to increase the reliability of the measure as there is a degree of objectivity in such a system, plus the use of the clinical data makes comparison between samples relatively straightforward. Analysis of MRI scans however is, to some extent, open to interpretation which would affect the validity of the findings. 

To conclude, the use of brain imaging technologies can shed light on phenomena that could otherwise remain a mystery: the correlates of PFC and impulse control and posterior hippocampus and spatial navigation. What these technologies lack in explaining why specific activity/changes occur is more than made up for in the glimpses they provide as to the structure and activity of the brain; insight that can enable researchers to point with increasing certainty to the relationship between the brain and behaviour.

Two techniques are identified and some justification of techniques generally is provided. Critical thinking is shown in the final sentence.

Relevant research is linked to a specific technique. Some relevant study detail is used. The aim of the study is explained; the technique (PET scan) is explained.

The sample is explained and linked to the behaviour and PFC.

‘Discuss’ command term addressed via critical thinking.

Findings presented along with conclusion - both of these are analysed with respect to the ‘Discuss’ command term.

Alternative explanations considered.

A second technique (MRI) is described and discussed: strengths and limitations are given

A relevant study is used to further demonstrate the use of MRI. Expansion of points in line with the ‘Discuss’ command term.

Detail as to the analysis of MRI scans shows good technical knowledge with critical thinking embedded.

The conclusion pulls together what the essay has covered and ends with a critique which links back to the question.

An ERQ should be around 800 words long.

Word count: 872

[22 marks]