Maguire

• Background

  • Brain plasticity is the capacity of the brain to modify the organization of its neural networks according to the particular experiences of the body.
  • It refers to the brain's ability to change throughout life.
• Background

  • The hippocampus is one of the major structures of the limbic system.
• Background

  • The hippocampus is the part of the brain linked to the conversion of information from short-term to more permanent memory.
  • It is found inside each hemisphere of the brain and is thought to play an important role in facilitating spatial memory and navigation.
  • This is clear evidence of localisation of function.
• Background

  • The anterior hippocampus (the front part) is involved in new learning about environmental layouts.
• Background

  • The posterior hippocampus (the back) is involved in using previously learned information about the environment.
• Background

  • The left side of the hippocampus holds memories for events. The right side holds our mental maps.
• Background

  • MRI scans involve the use of radio waves to obtain 3D images of the brain.
• Pixel Counting

  • This is a technology which analyses the MRI into 2D.
  • In Maguires study it was used to check the VBM.
  • It involves analysing the photographic slices of the hippocampus and counting the pixels from each slice.
  • This was then multiplied by the distance between each slice to find the hippocampal volume.
• Voxel Based Morphometry (VBM)

  • This is modern technology which analyses the MRI scan into 3D.
  • It identifies differences in density of the grey matter in the brain.
  • The denser the area, the more neural connections that exist.
  • This would suggest greater use of this area of the brain.
• The key theme is Brain Plasticity.
• Aim

  • To show that the hippocampus in the human brain is the structure associated with spatial memory and navigation.
• Sample

  The experimental group was made up of 16 taxi drivers. These were all:

  • Healthy
  • Male
  • London taxi drivers
  • Right-handed
• Sample

  • The mean age of the London taxi-drivers was 44.
  • the mean time as a licensed London taxi driver was 14.3 years.
• Sample

  • A control is that the taxi drivers had no medical, neurological, or psychological health problems.
• Sample

  • A control group was drawn from the MRI database at the University College London.
  • These controls did not drive taxis.
  • A matching process was done on the basis of health, right-handedness, sex, mean age and age range.
• Sample

  • There were 50 participants in the final matched control group who were used for the final VBM analysis to compare their brain activity with that of the taxi drivers.
  • A final cut of 16 of the 50 (who were precisely matched in age to the 16 taxi drivers) were used the compare the taxi drivers' pixel counting analysis.
• 'The Knowledge'

  • This is the training given to potential taxi drivers to allow them to have a detailed knowledge of the 25,000 streets within a 6 mile radius of Channing Cross in London.
• Research Method

  • This was a quasi experiment.
• Research Method

  • The IV was whether the participant was a London taxi driver or a person who did not drive taxis.
  • This was naturally occurring and could not be manipulated.
• Research Method

  • The DV was the volume of the hippocampi, including the anterior, body and posterior regions.
  • This was measured by analysing MRI scans of participants' brains using the two techniques VBM and pixel counting.
• Procedure

  • The taxi drivers were individually given an MRI scan at The Wellcome Department of Cognitive Neurology- University College London.
• Procedure

  • VBM (voxel based morphometry) is an automatic procedure which 'normalises' the scans to a template to eliminate overall brain size as a variable.
• Procedure

  • The images were analysed by one person experienced in the technique and blind to whether the scan was of a taxi driver or a control and the VBM findings.
  • The procedure allowed the total hippocampal volume to be calculated.
• Results

  • Overall there is no difference in the volume of the body of the hippocampus between taxi drivers and non-taxi drivers.
• Results

  • Both groups had significantly greater hippocampal body volume on the right than the left hemisphere.
  • Both groups had significantly greater anterior right hippocampal volume compared to their anterior left.
• Results

  • Taxi drivers have greater volume in their posterior hippocampus compared to the controls, showing more use of previously stored knowledge (eg using more mental maps).
• Results

  Taxi drivers also had slightly greater volume in their posterior hippocampus in the right side than the left side.
• Results

  • Control groups had greater volume in their anterior hippocampus compared to taxi drivers.
  • This is thought to be a 'trade-off' for taxi drivers having a large store of mental maps.
  • Taxi drivers may be less able to learn new information that controls because their brain capacity is tied up with 'The Knowledge'.
• Results

  • A correlational analysis was conducted to see if there is a relationship between size of the hippocampus and how long taxi drivers have been in the job.
  • This was to see if experience seems to lead to increase in volume- does the brain change?
• Results

  • There is a positive correlation between the volume of the posterior hippocampus and time served as a taxi driver.
  • This means that as time increases as a taxi driver, so does the volume of the posterior hippocampus.
• Results

  • There was a negative correlation between the volume of the anterior hippocampus and time as a taxi driver.
  • This means that as their time as a taxi driver increases, the volume of their anterior hippocampus decreases.
• Results

  • The results of the correlational analysis between time as a taxi driver and volume of the hippocampus supports the idea that the brain can adapt and change depending on environmental contexts (brain plasticity).
• Results

  • The results from the pixel counting support the results from the VBM.
  • This shows external reliability and concurrent validity.
• Result- Taxi drivers had significantly more grey matter in their posterior hippocampus than controls.


  Conclusion- There are regionally specific structural differences between the hippocampi of licensed taxi-drivers compared to those who do not drive taxis.
• Result- Controls had a significantly greater anterior right hippocampal volume than the taxi drivers.


  Conclusion- It can be suggested that changes in hippocampal grey matter are acquired i.e. due to nurture.