1. Maguire Physiological Psychology The Core Studies

2. Background MRI Scanner – Shows the size and volume of the brain and produces a colour photo of the brain in action. MRI Scanner (in the study) - measured the volume of grey matter in the hippocampi of taxi and non taxi drivers. Hippocampus - The hippocampus is the region of the brain that deals with spatial memory and navigation. Neuroplasticity – The ability of the brain to change depending on how much we use certain areas of it The Knowledge – An exam for London taxi drivers. Takes 2 years to pass. Written & practical

3. Background Why Maguire chose London taxi drivers : London is considered to have difficult routes, she knew all had similar experiences and a basic level of knowledge for all of the routes VBM (voxel based morphometry) : Identifies differences in the density of grey matter in different parts of the brain Pixel Counting : Identifies hippocampal volume as a function of total brain size. It consists of counting the pixels in images provided by MRI scans. Grey matter – Part of the brain (deep in the hippocampus) that is the most dense in neural cells and is associated with higher order thinking

4. Aim To demonstrate that the hippocampus is the region of the brain associated with spatial memory and navigation.

5. Sample 16 right-handed, male, licensed London taxi drivers, aged between 32-62 years, mean age 44 years. All had been licensed London taxi drivers for more than 1.5 years (mean time as a taxi driver = 14.3 years) All of the taxi drivers had healthy general medical, neurological and psychiatric profiles. These were matched by health, mean age, age range, gender and right-handedness with 50 non-taxi drivers drawn from a structural MRI scan database at the same unit where the taxi drivers were scanned. Why both were used: Because taxi drivers have extensive experience of spatial navigation, scans of their brain were compared with scans of non-taxi drivers who do not have the same spatial navigation experience to see if there were any structural hippocampal differences

6. Method Lab experiment Snapshot study Matched Pairs IV = London taxi driver (brain) or non-taxi driver (brain). DV = Structure of hippocampi or volume/distribution/density of grey matter in hippocampus. Controls: Same expert always analysed the MRI scans, all were scanned using the same MRI scanner, all right handed WHY? To make it a fair test so the characteristics of the taxi drivers and non-taxi drivers are similar e.g. age/handedness etc.

7. Procedure Structural MRI scans were obtained with a 2.0 Tesla Vision system for all participants – both taxi and non-taxi drivers. Two image analysis methods were then used to analyse the data/scans: (i) VBM (voxel- based morphometry) was used to examine whether morphological changes associated with navigation experience were detectable in the healthy human brain of the 16 taxi drivers and 50 non-taxi drivers. It is an automatic procedure which, with Statistical Parametric Mapping, identifies differences in the density of grey matter in different parts of the brain; (ii) pixel counting was then used to analyse the data from the 16 taxi drivers and 16 precisely age-matched non-taxi drivers so the hippocampal volume could be calculated. The images produced by the MRI scans were analysed by one person who counted the pixels in each slice. This person was blind to whether a participant was a taxi driver or a non-taxi driver, and also blind to the VBM findings. Comparisons were then made between the findings from the scans of the taxi drivers and those of non-taxi drivers.

8. Results The length of time spent as a taxi driver correlated positively with the volume of the right posterior hippocampus. The length of time spent as a taxi driver correlated negatively with the volume of the anterior hippocampus. Taxi drivers had a greater posterior hippocampal volume than non-taxi drivers. Significantly increased grey matter volume was found in the brains of taxi drivers compared to those of non-taxi drivers in 2 brain regions, namely the right and left hippocampi.

9. Conclusions Scientific evidence that the hippocampus is involved in navigation Scientific evidence that neural plasticity is evident in humans The posterior hippocampus stores spatial information and grows larger with more usage The posterior is different (function wise) to the anterior

10. Strengths of the study Very reliable and replicable (standardised procedure, scientific equipment) Highly controlled so we can establish that no extraneous variable affected the DV. Cause and effect can be established. Precise scientific quantitative data – groups can be meaningfully compared and statistical analysis can be carried out Small sample – very precise

11. Weaknesses Not generalizable to women, left handed male taxi drivers, left handed non taxi drivers etc… We do not gather information about why the posterior hippocampus and anterior are different between people

12. Evaluation of sample All taxi drivers passed the knowledge which means when assessing the hippocampal volume, results will be valid Small sample = precise and detail However, not generalizable enough

13. Evaluation of method Lab based so very scientific and reliable High control = no extraneous variables, reliable However does not give us reasons as to why the hippocampus volume differs between people so the study has unanswered questions, perhaps too artificial

14. Changes to the study Compare the results to left handed people, women etc… Take a sample from taxi drivers in another city Make the sample larger so more representative See if the knowledge is responsible for the hippocampal changes – scan before and after