A Commentary of …

Navigation-Related Structural Change in the Hippocampi of Taxi

Drivers

Maguire, E.A., Gadian, D.G., Johnsrude, I.S., Good, C.D., Ashburner, J., Frackowiak, R.J.,

and Frith, C.D.

MARRY

Presented by Group B5:

Nidhi Bhusha, Marry Fernam, Amina Nawaz, Rachel Wallace and Rory Wasserman

Commentary Presentation…

Overview

MARRY

• Key Terms

• Positive Comments

• Criticisms

• Follow-up Studies

• Class Discussion

Summary of Study…

Key Terms

MARRY

•The KnowledgeExtensive taxi driver training of London streets, major routes and landmarks; it takes approximately 2 years to acquire

•Cohort effectSimilarities in a group due to common temporal experience or common life experiences

Maguire, E.A., et al. (2000). Navigation-related structural change in the hippocampi of taxi drivers [see comments]. Proc Natl Acad Sci USA, 97, 4398-4403.

Positive Critiques…

Specificity of Test Subjects

MARRY

Experimental: 16 right-handed male taxi drivers between the ages of 32 and 62 years old, in occupation for a minimum of 18 months

Control: 50 healthy, right-handed male non-taxi drivers

• Ensured to use subjects with healthy bodily and mental profiles• Prevented most size differentials due to sex, age, or physical illnesses from influencing results

Maguire, E.A., et al. (2000). Navigation-related structural change in the hippocampi of taxi drivers [see comments]. Proc Natl Acad Sci USA, 97, 4398-4403.

Positive Critiques…Utilization of Two Independent Imaging

Techniques to Observe Changes in Size

MARRY

Voxel Based Morphometry (VBM) with statistical parametric mapping: calculated volumetric differences in brain matter of subject MRI scans from a template control

Pixel counting: volume calculated by adding all cross-sectional areas and multiplying by the distance between adjacent MRI scans

• Results from VBM could be further verified with results from pixel counting• Further contributed to the reliability of results

Maguire, E.A., et al. (2000). Navigation-related structural change in the hippocampi of taxi drivers [see comments]. Proc Natl Acad Sci USA, 97, 4398-4403.

Critiques…

Possible Areas of Improvements

MARRY

• Assessing subjects’ psyches

• Non-taxi drivers: occupations?

• Role of stress

Critiques…

Vagueness of the Term “Mental Map”

RORY

• Maguire and others proposed that the larger hippocampus size in taxi drivers was due to their “spatial representation of London” or their “mental map””

• There is a potential problem with the vagueness of the term “mental map”

• Other Research has suggested the role of the hippocampus is more specific

Maguire, E.A., et al. (2000). Navigation-related structural change in the hippocampi of taxi drivers [see comments]. Proc Natl Acad Sci USA, 97, 4398-4403.

Critiques…

Side Road Memory

RORY

• The hippocampus may be involved specifically with SIDE ROAD memory

• A 2006 Maguire Study of Patient TT

Patient TT:• A retired London Taxi Driver with 37 years experience• Primarily bilateral hippocampus damage due to limbic encephalitis

Maguire, A., Nannery, R., and Spier, H. (2006). Navigation around London by a taxi driver with bilateral hippocampal lesions. Brain. 129, 2894-2907.

Critiques…

Side Road Memory

RORY

• TT retained a large amount of navigationally-relevant information

• Normal landmark recognition, and relational and orientation knowledge about central London

Used a video game simulation of London to test his ability to navigate London

‘The Getaway’ 2002 Sony Computer Entertainment Europe

Critiques…

Side Road Memory

RORY

• Was able to navigate virtual London surprisingly well

• However had considerable difficulty when the routes required Non-A Roads

• A-Roads are the major arteries of London

The Orange Roads are A-Roads

Maguire, A., Nannery, R., and Spier, H. (2006). Navigation around London by a taxi driver with bilateral hippocampal lesions. Brain. 129, 2894-2907.

Critiques…

Non A-Road Deficit

RORY

Clear Deficit on routes that could be navigated without A-Roads

Main Arteries of city become semantic knowledge non-A roads are episodic?

Maguire, A., Nannery, R., and Spier, H. (2006). Navigation around London by a taxi driver with bilateral hippocampal lesions. Brain. 129, 2894-2907.

Critiques…

Landmark Memory

RORY

A Toronto study: Possible role of hippocampus for landmark memory?

Patient SB• Taxi driver in downtown Toronto for 30 yrs and courier in downtown Toronto for 15 yrs• Hippocampus damage due to Alzheimer's disease• Impaired memory for recently learned items

Rosenbaum, R., Gao, F.,Richards, B., Black, S., and Moscovitch, M. (2005). ‘‘Where to?’’ Remote Memory for Spatial Relations and Landmark Identity in Former Taxi Drivers with Alzheimer’s Disease and Encephalitis. Journal of Cognitive Neuroscience.

Critiques…

Landmark Memory

RORY

• SB had intact navigational abilities based on remote spatial memory

• Was able to devise an alternate route to avoid a detour, and Complete vector-mapping tests for orientation and distance

Had an understanding of where landmarks were in the city, and How to get from one landmark to another

HOWEVER: Could not recognize Toronto or World Landmarks, and could not identify them

Rosenbaum, R., Gao, F.,Richards, B., Black, S., and Moscovitch, M. (2005). ‘‘Where to?’’ Remote Memory for Spatial Relations and Landmark Identity in Former Taxi Drivers with Alzheimer’s Disease and Encephalitis. Journal of Cognitive Neuroscience.

Critiques…

Landmark Memory

RORY

Rosenbaum, R., Gao, F.,Richards, B., Black, S., and Moscovitch, M. (2005). ‘‘Where to?’’ Remote Memory for Spatial Relations and Landmark Identity in Former Taxi Drivers with Alzheimer’s Disease and Encephalitis. Journal of Cognitive Neuroscience.

RORY

Google Earth

LONDON PROPERTY GROWTH

Created by “Barnabu”

http://www.barnabu.co.uk  

Timeline of the 60 tallest buildings to be created and demolished in London over the last 50 years

Critiques…

Changing London

AMINA

• Landmarks and side roads change much more rapidly than the main arteries of a city

• London has experienced rapid growth in the past few decades

Maguire, E.A., et al. (2000). Navigation-related structural change in the hippocampi of taxi drivers [see comments]. Proc Natl Acad Sci USA, 97, 4398-4403.

Critiques…

Possible Explanations of Maguire’s Results

RORY

Possible Causes:

•Cohort effect?

•More time as Taxi Driver = More changes in London

Maguire, E.A., et al. (2000). Navigation-related structural change in the hippocampi of taxi drivers [see comments]. Proc Natl Acad Sci USA, 97, 4398-4403.

Critiques…

The Knowledge

AMINA

• 25,000 streets

• Know all points of interest, such as theatres, hospitals, railway stations, police stations, courts, shopping centers, etc.

• Know the names and order of the side streets, and traffic signals and regulations passed on the route

"The Knowledge”, Public Carriage Office, Transport for Londonhttp://www.tfl.gov.uk/businessandpartners/taxisandprivatehire/1412.aspx

Critiques…

Maguire’s Approach

AMINA

•Instead of testing out the predisposition notion, Maguire makes the assumption that the hippocampi of London taxi drivers were of average size initially.

• A far better approach would be include subjects just starting their training, and subjects at month 0 on the job.

• Or a longitudinal study to more accurately eliminate any individual differences between subjects.

Maguire, E.A., et al. (2000). Navigation-related structural change in the hippocampi of taxi drivers [see comments]. Proc Natl Acad Sci USA, 97, 4398-4403.

Follow up Studies…

London Taxi Drivers & Bus Drivers: Structural MRI & Neuropsychological Analysis

RACHEL

Question

Gray matter differences…

Are they really a result of spatial representations over time or does driving experience and/or stress play a role?

Maguire, E.A., Woollett, K., Spiers, H.J. (2006). London Taxi Drivers and Bus Drivers: A Structural MRI and Neuropsychological Analysis. Hippocampus, 16, 1091-1101.

Follow up Studies…

London Taxi Drivers & Bus Drivers: Structural MRI & Neuropsychological Analysis

RACHEL

Results

•Bus drivers were not found to have a difference in gray matter volume related to years of driving experience

•Stress did not differ in bus drivers versus taxi drivers

•Taxi drivers were found to better at naming London landmarks and knowing their relative distances between compared to that of London bus drivers

Maguire, E.A., Woollett, K., Spiers, H.J. (2006). London Taxi Drivers and Bus Drivers: A Structural MRI and Neuropsychological Analysis. Hippocampus, 16, 1091-1101.

Follow up Studies…

London Taxi Drivers & Bus Drivers: Structural MRI & Neuropsychological Analysis

RACHEL

Conclusions

Large amount of spatial information and the variety of destinations and start sites requires reconfiguring of that information by taxi drivers could be responsible for the increased volume of the hippocampus

Maguire, E.A., Woollett, K., Spiers, H.J. (2006). London Taxi Drivers and Bus Drivers: A Structural MRI and Neuropsychological Analysis. Hippocampus, 16, 1091-1101.

Follow up Studies…

Non-Spatial Expertise and Hippocampal Gray Matter Volume in Humans

RACHEL

Question

Can this hippocampus volume size difference be attributed simply to the large gaining of knowledge or was it the specifically large amounts of spatially specific information?

Woollett, K., Glensman, J. & Maguire, E.A. (2008). Non-Spatial Expertise and Hippocampal Gray Matter Volume in Humans. Hippocampus, 18, 981-984.

Follow up Studies…

Non-Spatial Expertise and Hippocampal Gray Matter Volume in Humans

RACHEL

Results•Doctors learn a large amount of non-spatial information in a given time period •Doctors were found to have NO correlation between number years worked and gray matter volume

ConclusionsDiffering hippocampal volumes can be seen when the knowledge acquired is explicitlyspatial and requiring great detail andprecision retrieval

Woollett, K., Glensman, J. & Maguire, E.A. (2008). Non-Spatial Expertise and Hippocampal Gray Matter Volume in Humans. Hippocampus, 18, 981-984.

Class Discussion…

AMINA

GPS navigation systems are becoming increasingly common and there is recent talk in London, of fitting such systems into the taxi cabs.  

If this study was repeated 50 years from now, how might the reliance on GPS affect results?

same size?

References

Maguire, E.A., et al. (2000). Navigation-related structural change in the hippocampi of taxi drivers [see comments]. Proc Natl Acad Sci USA, 97, 4398-4403.

Maguire, A., Nannery, R., and Spier, H. (2006). Navigation around London by a taxi driver with bilateral hippocampal lesions. Brain. 129, 2894-2907.

Maguire, E.A., Woollett, K., Spiers, H.J. (2006). London Taxi Drivers and Bus Drivers: A Structural MRI and Neuropsychological Analysis. Hippocampus, 16, 1091-1101.

Rosenbaum, R., Gao, F.,Richards, B., Black, S., and Moscovitch, M. (2005). ‘‘Where to?’’ Remote Memory for Spatial Relations and Landmark Identity in Former Taxi Drivers with Alzheimer’s Disease and Encephalitis. Journal of Cognitive Neuroscience.

"The Knowledge”, Public Carriage Office, Transport for Londonhttp://www.tfl.gov.uk/businessandpartners/taxisandprivatehire/1412.aspx

Woollett, K., Glensman, J. & Maguire, E.A. (2008). Non-Spatial Expertise and Hippocampal Gray Matter Volume in Humans. Hippocampus, 18, 981-984.