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The Maguire Page

Maguire, E. A., Gadian, N. G., Johnsrude, I. S., Good, C. D., Ashburner, J., Frackowiak, R. S., & Fith, C. D. (2000) Navigation-related structural changes in the hippocampi of taxi drivers.

On this page you should find lots of useful stuff to help you in your learning of the Maguire core study.

Here is the most important page. Click here for a summary and evaluation of the Maguire study.

This page has some Core Studies Section A past questions that you might want to practice. Please don?t email me for the answers.

Here is a fill in the gaps quiz to test your knowledge of the study.

And here is a great page on Jamie?s psychblog where you can read the original study and more.

 

 

Below is a much briefer summary of the Maguire et al. study.

Maguire et al. were attempting to demonstrate the plasticity of the brain. Plasticity (or neuro-plasticity) refers to changes that occur in the organization of the brain as a result of experience.

The researchers studied the hippocampus of London taxi drivers because they were interested to see if the hippocampus would change because of the taxi drivers? high dependence on navigational skills.

The hippocampus is a brain structure and humans and other mammals have two hippocampi, a left and right one. The hippocampus is located in the medial temporal lobe and belongs to the limbic system. The limbic system is the set of brain structures that forms the inner border of the cortex.

There is evidence to suggest that the hippocampus plays major roles in short term memory and spatial navigation.

Maguire et al. set out to discover whether morphological (changes in form and shape) changes could be detected in the healthy human brain associated with extensive experience of spatial navigation. Their prediction was that the hippocampus would be the most likely brain region to show changes.

To test this prediction the researchers decided to study London taxi drivers because they rely heavily on spatial navigation skills in their working lives. London taxi drivers have to undertake extensive training known as ?The Knowledge? and during this time they have to acquire a vast spatial memory of the roads of central London.

Aim

The aim of the study was to investigate whether changes could be detected in the brains of London taxi drivers and to further investigate the functions of the hippocampus in spatial memory.

Method/Procedure

The participants for this study were 16 healthy, right-handed male licensed London taxi drivers. The taxi drivers were compared with the scans of 50 healthy right-handed males who did not drive taxis

All of the participants had been licensed London taxi drivers for more than one and a half years

The average time spent training to be a taxi driver before passing the licensing tests fully (i.e., time on ?The Knowledge?) was 2 years

All of the taxi drivers were described as having healthy general medical, neurological, and psychiatric profiles.

The scans of the 50 control participants were selected from the structural MRI scan database at the same unit where the taxi drivers were scanned. Participants below 32 and above 62 years of age were excluded as were females, left-handed males, and those with any health problems.

The study is an example of a quasi or natural experiment because the researchers are comparing the data of taxi drivers and non-taxi drivers. The researchers have no control of this variable as it is naturally occurring.

The researchers also make use of correlation analysis as they are investigating a relationship between the brain scans and length of time the taxi drivers have been licensed.

The data were collected using structural magnetic resonance imaging (MRI) which collects data about the structure or anatomy of the brain. The MRI scanner works by exposing a participant?s brain to a strong magnetic field and radio waves to produce detailed pictures of the brain.

Computer software converts the information into a 3D image of the brain and in this study the analysis can calculate the amount of grey matter in the hippocampus.

Unlike white matter, Grey matter contains neural cell bodies. To use a computer analogy, the gray matter can be thought of as the actual computers themselves, whereas the white matter represents the network cables connecting the computers together The data were measured using two different techniques ? voxel-based morphemetry (VBM) and pixel counting.

Voxel-based morphology (VBM) was used in this study to measure the density of grey matter in the brain. VBM provides a three dimensional measurement of volume of an area.

Pixel counting was carried out on the scans of the 16 taxi drivers and 16 age-matched controls taken from the 50 control participants.

Pixel counting consists of counting the pixels in the images provided by the MRI scans. A pixel is simply a two dimensional measurement of an area. Areas were calculated by taking images of slices of the whole length of the hippocampus.

Results

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).

Explanations

Maguire et al. argue that this study demonstrates the plasticity of the hippocampus in response to environmental demands.

They argue that the posterior hippocampus stores a spatial representation of the environment and that in the London taxi drivers the volume of the posterior hippocampus expanded because of their dependence on navigation skills.

The authors believe that this study suggest that the changes in hippocampal gray matter?at least on the right?are acquired. This finding indicates the possibility of local plasticity in the structure of the healthy adult human brain as a function of increasing exposure to an environmental stimulus.

Maguire et al. argue that the anterior and posterior hippocampus have different roles. The posterior hippocampus is involved when previously learned spatial information is used, whereas the anterior hippocampal region may be more involved (in combination with the posterior hippocampus) during the encoding of new environmental layouts.

They also suggest that the left and right sides of hippocampus have different functions. They speculate that the right holds mental maps whereas the left hippocampus complements its partner by storing memories of people and events.

The authors note that this study has implications for the rehabilitation of those who have suffered brain injury or disease. If similar environment related plasticity is possible in other regions of the human brain outside of the hippocampus then such people may be helped in the future.