Maguire et al: Taxi Drivers

Brain Plasticity

The brain's ability to change and adapt due to experience

Hippocampus

Small, curved formation in the brian that plays an important role in the limbic system.

Limbic System

Part of the brain involved in our behavioural and emotional responses.

Spatial Navigation

A complex cognitive process, which draws upon almost all the fundamental elements in cognition including attention and perception, learning and memory, and reasoning and decision-making.

Natural Experiments

A study in which individuals are exposed to the experimental and control conditions that are determined by nature or by other factors outside the control of the investigators.

Voxel-based morphometry

An automated technique that transforms a brain scan from an individual to a standardized template, to find volumetric differences in small areas (voxels).

Pixel counting

2D measurement which counts pixels within three regions of the hippocampus; the posterior, the body and the anterior. It measures the grey matter volume. It identifies hippocampal volume.

Correlational analysis

a statistical method used to measure the strength of the linear relationship between two variables and compute their association. 

Henry Guastav Molaison case study

H.M. was a patient under Dr. William Scoville who believed that removing H.M.'s hippocampus would alleviate his epileptic seizures. While the surgery was successful, it led to H.M. suffering from anterograde amnesia, in which he could no longer form or keep new memories.

Lesion Studies:

Rats trained to run mazes are unable to navigate after having their hippocampi lesioned can’t remember the location of places or things.

Aims:

To examine whether structural changes could be detected in the brain of people with extensive experience of spatial navigation (taxi drivers)

To see if there is a correlation between length of taxi-driving experience and measure of grey matter volume. This will show the extent of brain plasticity

Samples: Group 1: Participants

• 16 participants in total

• All male

• All London taxi drivers (minimum 1.5 years experience)

• All right handed

• Aged between 32 and 62 (mean = 44)

• Healthy medical, neurological and psychiatric profiles

Samples: Group 2: The control

• 50 participants in total

• All male

• All do not drive taxis

• All right handed

• Aged between 32 and 62 (Mean age 44)

• Healthy medical, neurological and psychiatric profiles

RESEARCH METHOD:

Quasi field experiment; matched pairs design – matched on male, age and right handed.

PROCEDURE:

16 healthy, right-handed male London taxi drivers, age 32–62, licensed over 18 months. Control group: scans of 50

right-handed healthy males who don’t drive taxis from same MRI database.

● MRI scanners use radio waves and strong magnetic fields to produce detailed images of the structure of the body.

● Participants scanned separately in the same MRI unit. Once scans complete 2 procedures were used to check the

size of the grey matter in the hippocampus:

RESULTS QUANTITATIVE DATA (anterior = front; posterior = back):

● The posterior hippocampi of taxi drivers had a significantly larger volume compared to control subjects

● The anterior hippocampal region had a larger volume in control subjects than in taxi drivers.

● Posterior hippocampus volume correlated positively and anterior negatively with time as taxi driver.

● VBM analysis found no differences were observed elsewhere in the brain.

● Pixel counting found overall volume of whole hippocampus was same between groups.

CONCLUSIONS:

Maguire argued the study demonstrated plasticity of the hippocampus in response to environmental

demands (increased navigation needed as a taxi driver). The posterior stores a spatial memory of the environment and

so the volume increases in London taxi drivers because of their high use of navigational skills.