Maguire

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Background & Aim

  • Does the structure of your brain change in response to environmental demand?
  • The aim was to find out whether changes in the brain could be detected in those with extensive navigation experience.
  • Based on research suggesting that the role of the hippocampus is to facilitate spatial memory (navigation).
  • Maguire hypothesised that the hippocampi in London Taxi drivers will be structurally different to the hippocampi in non-taxi drivers.
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Method, Procedure & Controls

  • Natural/Quasi experiment: Independant Design/Matched Pairs Design.
  • Correlation: Between length of time taxi-driving and volume of grey matter.
  • Participants; Group 1:
  • 16 right handed
  • male taxi drivers
  • average age 44
  • all liscensed more than 18 months
  • average time as taxi driver 14.3 years.
  • Group 2:
  • 50 right handed
  • male
  • age matched
  • non taxi-drivers - chosen from a database at the same unit where the texi drivers were scanned.
  • IV: London Taxi driver (brain) or Non Taxi driver (brain)
  • DV: Structure and volume of hippocampi
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Method, Procedure and Controls (2)

  • Image acquisition: Structural MRI scans were obtained of the 50 non-taxi drivers to establish a comparison database of 'average hippocampi'.
  • The taxi drivers also scanned.
  • Analysis: Voxel-based morphology (VBM) used to measure the density of grey matter in the brain.
  • VBM provides 3D measurement of volume of an area.
  • Analysis: Pixel counting was carried out on 16 taxi-drivers and 16 age-matched non taxi drivers.
  • It is a 2D measurement of an area.
  • The scan was seperated into 26 slices.
  • Control: The expert conducting the analysis did not know whether MRI scan was of taxi driver brain or not.
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Results

  • The Voxel Based Morphology (VBM) found that taxi drivers have a greater volume of grey matter volume in their right posterior hippocampus.
  • Whereas, the control group had a greater volume of grey matter in their anterior hippocampus.
  • The pixel counting analysis supports these results.
  • Positive correlation: As the length of time a taxi driver had been driving increased, the volume of grey matter in the posterior hippocampus also increased.
  • As the length of time a taxi driver had been driving increased, the volume of grey matter in the anterior decreased.
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Conclusions & Implications

  • The structure of the brain changes in response to environmental demand.
  • The mental map of the city of London is stored in the posterior hippocampi in taxi drivers.
  • Normal activity can induce changes in the structure of the brain and that this has many implications for rehabilitation after brain injury.
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