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A Commentary of …

MARRY. 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. Presented by Group B5:

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A Commentary of …

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  1. MARRY 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. Presented by Group B5: Nidhi Bhusha, Marry Fernam, Amina Nawaz, Rachel Wallace and Rory Wasserman

  2. MARRY Commentary Presentation… Overview • Key Terms • Positive Comments • Criticisms • Follow-up Studies • Class Discussion

  3. MARRY Summary of Study… Key Terms • The Knowledge • Extensive taxi driver training of London streets, major routes and landmarks; it takes approximately 2 years to acquire • Cohort effect • Similarities 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.

  4. MARRY Positive Critiques… Specificity of Test Subjects • 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.

  5. MARRY Positive Critiques… Utilization of Two Independent Imaging Techniques to Observe Changes in Size • 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.

  6. MARRY Critiques… Possible Areas of Improvements • Assessing subjects’ psyches • Non-taxi drivers: occupations? • Role of stress

  7. RORY Critiques… Vagueness of the Term “Mental Map” • 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.

  8. RORY Critiques… Side Road Memory • 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.

  9. RORY Critiques… Side Road Memory • 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

  10. RORY Critiques… Side Road Memory • 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.

  11. RORY Critiques… Non A-Road Deficit 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.

  12. RORY Critiques… Landmark Memory • 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.

  13. RORY Critiques… Landmark Memory • 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.

  14. RORY Critiques… Landmark Memory 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.

  15. 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

  16. AMINA Critiques… Changing London • 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.

  17. RORY Critiques… Possible Explanations of Maguire’s Results • 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.

  18. AMINA Critiques… The Knowledge • 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 London http://www.tfl.gov.uk/businessandpartners/taxisandprivatehire/1412.aspx

  19. AMINA Critiques… Maguire’s Approach • 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.

  20. RACHEL Follow up Studies… London Taxi Drivers & Bus Drivers: Structural MRI & Neuropsychological Analysis 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.

  21. RACHEL Follow up Studies… London Taxi Drivers & Bus Drivers: Structural MRI & Neuropsychological Analysis 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.

  22. RACHEL Follow up Studies… London Taxi Drivers & Bus Drivers: Structural MRI & Neuropsychological Analysis 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.

  23. RACHEL Follow up Studies… Non-Spatial Expertise and Hippocampal Gray Matter Volume in Humans 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.

  24. RACHEL Follow up Studies… Non-Spatial Expertise and Hippocampal Gray Matter Volume in Humans 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 Conclusions Differing hippocampal volumes can be seen when the knowledge acquired is explicitly spatial and requiring great detail and precision retrieval Woollett, K., Glensman, J. & Maguire, E.A. (2008). Non-Spatial Expertise and Hippocampal Gray Matter Volume in Humans. Hippocampus, 18, 981-984.

  25. AMINA Class Discussion… 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?

  26. 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 London http://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.

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