Maguire Flashcards
Describe the sample used in the study by Maguire and give one limitation of the sample. (6)
- London taxi drivers
- 16 participants all right-handed men
- Mean age 44, age range 32-62
- Healthy medical, neurological and psychiatric profiles
- Limitation: cab drivers are not representative of the general population they have specific set of knowledge and experience. They did not include any female cab drivers or left-handed cab drivers and therefore we cannot generalise the findings to the general population.
Aim of the maguire study
To demonstrate that the hippocampus is the region of the brain associated with spatial memory and navigation.
Describe how behaviour was measured in the study by Maguire.
- Behaviour was measured through using structural MRI scans and these were analysed using tow techniques.
- VBM: technique enables every point of the brain to be examined in an objective and unbiased way,
- VBM identifies differences in the density of grey matter in different parts of the brain. Grey matter describes some parts of the brain – there is grey and white matter.
- Pixel counting: hippocampus volume was counted using a well established pixel counting technique.
- The pixels were counted in the images produced by the MRI scans. Each scan was a photographic slice made through the hippocampal region of Ps brains.
- There were at least 26 contiguous slices. Each slice was 1.5mm thick, therefore covering a total length of approximately 4cm.
- Images were analysed by one person experienced in the technique who counted the pixel in each slice.
- This person was blind to whether the P was a taxi driver or control and also blind to the VGM findings.
- In the final analysis only 24 slices were used. Total hippocampal volume was calculated by adding up the pixels from each slice and multiplying this by the distance between adjacent slices.
- Finally a correction was made in relation to the total intracranial volume.
- This was done to account for the fact that some people have larger brains than others and therefore we would expect their hippocampi to be correspondingly bigger.
d) Explain how the reliability of these measurements could be assessed. (6)
- Inter-rater reliability - Comparing the analysis made by two experienced persons and calculating agreement
- Making sure that both persons are blind to whether the participant is taxi driver or control and blind to the VBM findings.
- Repeat the same scanning technique with the same group of participants and if the data gathered is the similar or the same as the previous, then results are reliable.
e) Outline the results of the study by Maguire. (8)
• VBM: Comparing the taxi-drivers to the controls there were only two brain regions with significantly increased grey matter – the right and left hippocampi.
• No differences were observed anywhere else in the brain.
• In the taxi-drivers the increase was limited to the posterior hippocampi.
• In the controls there was relatively more grey matter in the anterior hippocampi than there was in the brains of the taxi drivers.
• Pixel counting: there was no significant difference between the taxi-drivers and the control group in terms of 1) intracranial volume and 2) total hippocampal volume
• However there were differences in specific regions of the hippocampus:
Controls: - anterior right hippocampus larger on right than left than in taxi drivers
- Body of the hippocampus larger on the right than the left
Taxi driver: - posterior hippocampus larger than controls
• Results with regards to changes with navigation experience:
• Correlations were examined between the amount of time spent as a taci driver and volume of specific brain regions.
• Time spent as a taxi driver was positively correlated with the volume of the right posterior hippocampus
• Time spent as a taxi driver was negatively correlated with the volume of the anterior hippocampus.
f) Suggest two changes to the study by Maguire and outline how these changes might affect the results. (8)
- First change: (Sample) Use female right-handed cab drivers to see whether the data gathered from this sample support the results of Maguire’s study and in turn demonstrate that the hippocampus is the region of the brain associated with spatial memory and navigation.
- Imp on results: Results can be applied to women cab drivers
- Results are likely to show that in the female taxi drivers there is a significantly greater volume in the anterior hippocampus.
- Second change: (Different method) Snap shot study of male and female taxi drivers at beginning of their taxi training, half-way, when they qualify and finally when they are experienced taxi drivers. This way researchers can track the gradual changes in the volume of the hippocampus.
- Imp on results: Results will support Maguire’s findings
- Results of scanning techniques at the start of training and after many years of experience will show a significant increase in the volume of the hippocampus.
- Results cannot be generalised to the general population but now can be applied to female taxi drivers.
- a) Explain why Maguire used taxi drivers in their study of spatial memory. (2)
b) Identify two criteria used to select the taxi-drivers as participants in this study. (2)
• London taxi drivers were used because their work involves spatial memory and navigation. Spatial memory and navigation are thought to be associated with the region of the brain called the Hippocampus, which the researchers aim to demonstrate a link between.
Two criteria used to select the taxi-drivers as participants for this study were…
Any two from the following:
Two criteria used to select the taxi-drivers as participants for this study were…
• Right-handed males
• Aged between 32-62
• Healthy medical, neurological and psychiatric profiles.
- a) Describe one finding from this study. (2)
b) Suggest how the findings from this study might be used. (2)
Any one of the following findings:
• The first main findings of the research were that the posterior hippocampi of taxi drivers were significantly larger relative to those of control subjects and that the anterior hippocampal region was larger in control subjects than in taxi drivers.
• The second main finding was that hippocampal volume correlated with the amount of time spent as a taxi driver (positively in the right posterior and negatively in the right anterior hippocampus).
• The posterior hippocampus seems to be related to the previously learned spatial information.
• The anterior hippocampus may be more involved in encoding new information.
• The findings can be used fro rehabilitating people who have suffered brain damage. This can be done by making demands on the brain so that it may respond by enlisting the use of grey matter from other regions.
- Outline two major ideas of the biological approach to psychology that are in the study by Maguire. (4)
- One idea is that behaviour and experience can be explained by physiological changes.
- Another idea is that to use sophisticated equipment such as MRI scanners to provide an objective and precise way of measuring brain structure.
- Outline one control that was used in the study on brain scanning by Maguire and explain why it was important to use this control. (2)
• Researchers did not include any women taxi-drivers in their sample. This is a possible confounding variable which can affect the results of the study, as previous research demonstrates that men have a larger hippocampal volume than men.
- The study by Maguire used the biological technique of brain scanning.
a) Describe one commonly used brain scanning technique. (2)
b) Suggest one reason why results gained from such biological scanning techniques should be treated with caution. (2)
- CAT (Computerised axial tomography): Cat scans are built up from taking series of x-rays 180 degrees around the head. Images show areas of damage and will highlight for example where a person has experienced a cerebral haemorrhage (a type of stroke).
- MRI (Magnetic Resonance imaging): people slid into a machine, subjected to a strong magnetic filed which is turned of and off rapidly in the presence of a radio wave. Atoms of the brain change their alignment because of the magnetic filed when it is on and produce characteristic radio signals when it is off. A detector reads those signals and can map the structure of tissue.
- fMRI (Functional magnetic resonance imaging): fMRI scans use MRI technology to measure the changes in the blood oxygen levels that are connected to neural activity in the brain or spinal cord.
- PET (Positron emission tomography): Patients injected with slightly radioactive glucose. The most active brain tissue uses the glucose and so attracts the radioactive substance. Radiation sensors detect where radiation is greatest and so build up a picture of activity in the brain.
• Results should be treated with caution because there is the issue with being able to interpret what the scans tell us and recognise what they cannot tell us.
- a) In the study by Maguire describe one method used to analyse the brain scans. (2)
b) Describe one result obtained using this method. (2)
- VBM (Voxel-based morphology): identifies differences in the density of grey matter in different parts of the brain. Grey matter describes some parts of the brain, it lies on the surface of the brain also deep inside the structures such as the hypothalamus and hippocampus.
- Pixel counting: a pixel is a single point on a graphic image. The pixels were counted in the images produced by the MRI scans. Each scan was of a photographic slice made through the hippocampal region of participants’ brain.
VBM result:
- Comparing the taxi-drivers to the controls there were only two brain regions with significantly increased grey matter – the right and left hippocampi. No difference observed anywhere else in the brain.
- In the taxi-drivers the increase was limited to the posterior hippocampi. In the controls there was relatively more grey matter in the anterior hippocampi than there was in the brains of the taxi-drivers.
Pixel counting:
1. There was no significant difference between the taxi-drivers and the control group in terms of 1) intracranial volume and 2) total hippocampal volume.
2. however there were differences in specific regions of the hippocampus:
Controls
• anterior right hippocampus larger on right than left
• body of the hippocampus larger on the right than the left
Taxi drivers
• posterior hippocampus larger than controls
- Maguire found a positive correlation in their study of taxi-drivers’ brains.
a) Explain the term ‘positive correlation’, using examples from this study. (2)
b) State one conclusion that can be drawn from this result. (2)
• Positive correlation means both that both variables increase together. For example time spent as a taxi-driver was positively correlated with the volume of the right posterior hippocampus.
)
• It can be concluded from this result that the hippocampus is associated with spatial memory and navigation. OR
• It can be concluded that the length of time spent as a taxi-driver determines the volume of the right posterior hippocampus.
