Maguire et al. (2000)

Navigation-related structural change in the hippocampi of taxi drivers.

Background information: According to Maguire, the role of the hippocampus is to facilitate spatial memory, in the form of navigation. From previous studies (pre-Maguire) it was impossible to know whether differences in brain anatomy are predetermined, or whether the brain is susceptible to plastic changes, in response to environmental stimulation – in this case driving a taxi.

Taxi drivers undergo extensive training, known as ‘The Knowledge’ and therefore make an ideal group for the study of spatial navigation.

Aim: To examine whether structural changes could be detected in the brain of people with extensive experience of spatial navigation.

Method: Structural MRI scans were obtained. 16 right-handed male London taxi drivers participated; all had been driving for more than 1.5 years. Scans of 50 healthy right-handed males who did not drive taxis were included for comparison. The mean age did not differ between the two groups.

Results: 1) Increased grey matter was found in the brains of taxi drivers compared with controls in two brain regions, the right and left hippocampi. The increased volume was found in the posterior (rear) hippocampus.

2)Changes with navigation experience – A correlation was found between the amount of time spent as a taxi driver and volume in the right posterior hippocampus.

Conclusion: The results provide evidence for structural differences between the hippocampi of London taxi drivers and control participants, therefore suggesting that extensive practice with spatial navigation affects the hippocampus.

Evaluation:

Could this particular arrangement of hippocampal grey matter predispose individuals to professional dependence on navigational skills?This notion was tested directly, by examining a correlation between hippocampi volume and the amount of time spent as a taxi driver. Right posterior hippocampal volume positively correlated with the amount of time spent as a taxi driver and therefore suggests that changes in hippocampal volume are acquired.

As such, the finding indicates the possibility of local plasticity in the structure of the healthy adult human brain, as a function of increased exposure to an environmental stimulus. The results suggest that a mental map of London is stored in the posterior hippocampus and is accommodated by an increase in tissue volume.

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