Maguire

• Background: What did previous research show?

  • Previous research showed that small mammals and birds have an increased volume of hippocampus who show spatial memory behaviour (store food), and is especially large where lots of spatial memory behaviour occurs
  • There is differences between healthy structures of human brains e.g. between males and females
• Background: What has research not shown?

  • Whether differences in brain structure is because of environmental situation
  • The role of the hippocampus in humans
  • Whether humans respond to situations needing spatial memory in the same way as small mammals and birds
  • Maguire aimed to show that the hippocampus is linked to spatial memory and navigation
• What was the method?

  • Quasi experiment (taxi driver or not naturally occurring)

  IV - Taxi driver or non-taxi driver

  DV - Volume of hippocampi measured by analysing MRI scans using VBM and pixel counting

  • Independent measures
  • Matched pairs design
• What was the sample?

  • 16 healthy right handed male London taxi drivers
  • Mean age of 44
  • Been licensed London taxi driver for averagely 14.3 years

  Control group:

  • 50 participants who were matched for health, right handedness, sex, age range and mean age
  • Used as a control for individual differences
• Background: What is the role of the hippocampus?

  • Spatial memory and navigation
  • Role in helping London taxi drivers navigate the city
• Background: What were the taxi drivers required to do to be licenced?

  • Black cabs required to have detailed knowledge of 25,000 streets within 6 mile radius of Charing Cross and a general knowledge of London
  • Given written test on the first 80 routes and interviewed on the other 240
• What were the aims?

  • To investigate the role of the hippocampus in navigational and spatial skills and the extent the brain shows changes when exposed to navigational experience
  • To see if there is a correlation between the length of taxi driving experience and measure of grey matter volume
• What was the procedure?

  • Used structural MRI scanner

  Analysed with:

  1. Voxel - based Morphometry (VBM) - identifies differences in the density of grey matter in different parts of the brain
  2. Pixel counting - to calculate the hippocampus volume, pixels were counted on photographic slices made through the brain using MRI

  • The person counting pixels was blind to whether the brain belonged to the taxi driver condition or control group (method of control)
  • Pixels were counted for the anterior, posterior and body of the hippocampus
• What were the controls?

  • All scanned using the same scanner
  • Calculated hippocampus volume for each participant to include an adjustment for the size of each person's brain - ensures data is comparable
• Results: Volume

  • Taxi drivers have more grey matter volume in the posterior right hippocampus (measured by VBM) 
  • Control group had greater volume in anterior hippocampus 
  • Significant at p < 0.05 
• Results: Correlation

  • There is a positive correlation between grey matter volume in posterior right hippocampus and time as a taxi driver 
  • r = 0.6 , p < 0.05
• What were the conclusions?

  • Dependence on navigational skills is associated with movement of grey matter in the hippocampus 
  •  There are regionally specific structural differences between hippocampi of licensed London taxi drivers compared to those who do not drive London taxis 
  • Changes in the arrangement of hippocampal grey matter are acquired