London Taxi Drivers and Bus Drivers: A Structural MRI and Neuropsychological

Analysis

E.A. Maguire, K. Wollett & H.J. Spiers

Taxi VS Bus

Background

• Taxi Drivers• “The Knowledge”–2-4 yr training –25,000 streets!

• Bus drivers•Approx. 6 weeks of training•Drive ~12 set routes

MRI taxi drivers (Maguire et. al. 2000)

• MRI shows– ↑ gray matter volume in p. hippocampus– ↓ gray matter volume in a. hippocampus

• ↑ yrs driving taxi ↑ p. hippocampus & ↓ a. hippocampus!

MRI of Hippocampus (Maguire et. al. 2000)

Current Study: Is hippocampal ∆ really from spatial learning?

• Driving around London requires:– Vigilance– Attention– Motor planning– Execution– Stress

• May have impact on hippocampal gray matter?!• Is “The Knowledge” acquired at some expense?

Enter the Bus drivers!

• Taxi vs. Bus drivers– To “control” for self-motivation, driving

experience & stress on gray matter volume• Taxi– Free movement

• Bus– Set route

Who?•18 Taxi drivers•17 Bus drivers

Neuropsychological Tests

• Assessed – Basic cognitive memory– Working memory– Attention– Digit span (7 +/- 2)

– Stress– Recognition • London land mark test• In London (yes/no) & which landmark closer

Perceived stress scale example• 1. In the last month, how often have you been upset because of something that

happened unexpectedly?• ___0=never ___1=almost never ___2=sometimes ___3=fairly often ___4=very often

2. In the last month, how often have you felt that you were unable to control the important things in your life?

• ___0=never ___1=almost never ___2=sometimes ___3=fairly often ___4=very often • 3. In the last month, how often have you felt nervous and "stressed"?• ___0=never ___1=almost never ___2=sometimes ___3=fairly often ___4=very often • 4. In the last month, how often have you felt confident about your ability to handle

your personal problems?• ___0=never ___1=almost never ___2=sometimes ___3=fairly often ___4=very often • 5. In the last month, how often have you felt that things were going your way?• ___0=never ___1=almost never ___2=sometimes ___3=fairly often ___4=very often

From: http://www.macses.ucsf.edu/Research/Psychosocial/notebook/PSS10.html

Procedure

• Tested individually – One 2hr session– MRI & neuropsychological assessment in random

order

– 2 taxi drivers quit (claustrophobia in MRI)

http://www.youtube.com/watch?v=7g5UVrOt2CI

Results

• Taxi drivers compared to Bus drivers–Greater gray matter volume in

right/left mid-posterior hippocampi–Less volume in anterior head of

right/left hippocampi • NO difference in Caudate Nucleus

(learning & memory)

mpHippocampus

Coronal

Sagittal

Axial

Neuropsychological Tests

Neuropsychological Tests cont.

No difference in Stress/Anxiety

Not the reason for ∆ in Hippocampal size!

Taxi driving exp. on volume

Discussion

• This study confirms 2000 study• “The Knowledge” comes with a price –↓acquiring/retrieving new visuo-

spatial info

• ∆’s not due to stress

Discussion cont.

• “The Knowledge” becomes sharper with time– ↑Yrs driving taxi, ↑ p. hippocampi volume– Similar with musicians, jugglers & bilinguals

• Costs/Benefits?• Evolutionarily?• Beyond London?

Thank you