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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