Maguire - Taxi Drivers

Question 1

Effect of IV on DV

Answer 1

Taxi drivers has greater volume of grey posterior hippocampus than non-taxi drivers.
Less volume in anterior.

Question 2

Controls

Answer 2

1: TD & NTD = age matched
2: all male
3: pixel counter as blind to VBM results
4: all from same area, London.
5: all RIGHT handed

Question 3

Why is it important to use controls?

Answer 3

• prevent extraneous variables eg. Environmental differences/age/gender becoming confounding variables which might influence results eg. Differences in distribution of grey matter in hippocampus being due to a variable other than TD or NTD

Question 4

VBM

Answer 4

Pixel with 3 dimensions
Measure volume of specific brain areas by comparing each brain area to a template
MRI scans of 50 health male brains to produce template
VBM identifies differences in density of grey matter

Question 5

Pixel counting

Answer 5

Single point on graphical image
MRI scans made of slices through the hippocampi
2 dimensional
Analysed by one person who counted the pixels in each slice to produce a measure of hippocampal volume.
Blind to taxi driver or non taxi driver and VBM findings.

Question 6

Results VBM

Answer 6

Significantly more grey matter in both left and right hippocampi of taxi drivers than controls
Difference was only in posterior portion
Controls had relatively more in anterior
No difference observed elsewhere in the brain.

Question 7

Results pixel counting

Answer 7

Total hippocampal and intercranial volume did not differ significantly between taxi drivers and non-taxi drivers.
In the control the anterior RH and body of RH were larger than taxi drivers

Question 8

Changes with navigational experience

Answer 8

Positive correlation between time spent taxi driving and volume of posterior RH.
Negative correlation between time and volume of the anterior RH & LH.

Question 9

Sample

Answer 9

16 London male taxi drivers
Mean age 44
All licensed for more than 1.5 years
All healthy medical and neurological profiles

Control 50- not taxi drivers
Age matched… Control reduced to 16 after precise age matching.

Question 10

Sample

Answer 10

16 London male taxi drivers
Mean age 44
All licensed for more than 1.5 years
All healthy medical and neurological profiles

Control 50- not taxi drivers
Age matched… Control reduced to 16 after precise age matching.