PHYSIOLOGICAL PSYCHOLOGY

Maguire et al (2000)

Navigation- related structural change in the hippocampi of taxi drivers

Read pages 2 and 3 in your new Physiological Psychology

booklet while everyone getting settled

LESSON OUTCOMES

Recall the aims, method and results of the study

Identify the 4 lobes of the brain and their functions

Recognise the purpose and function of the hippocampus

WHAT IS PHYSIOLOGICAL PSYCHOLOGY? Physiological psychology focuses on the relationship

between our biological makeup and our behaviour and experiences.

How much do you think our biology affects us?

Reductionist argument – behaviour and experiences can be explained in terms of brain structure and chemicals

Opposing argument – Human behaviour and experience is too complex to simply explain in terms of brain structure and chemicals – what about other psychological variables…

A LITTLE BACKGROUND…

Physiological Psychology is:

The most scientific approach in psychology Mostly uses laboratory experiments Interested in the brain and nervous system Uses high tech equipment May use laboratory observations and

correlations

THE BRAINWhat do we know about the brain?

THE 10% MYTH

It has been suggested that we only use 10% of our brains

This is a belief held commonly amongst the general public, but few scientists

If 90% of our brain is not used then it shouldn’t matter too much if we get brain damage in that 90%

We know what a number of different parts of the brain are used for (Sperry) and there are few areas that appear inactiveThe idea that we only use 10% suggests that if we could somehow harness the other 90% we could almost make ourselves superhuman!

MAGUIRE ET AL (2000)

Maguire et al. were attempting to demonstrate the plasticity of the brain. Plasticity (or neuro-plasticity) refers to changes

that occur in the organization of the brain as a result of experience.

The researchers studied the hippocampus of London taxi drivers because they were interested to see if the hippocampus would change because of the taxi drivers high dependence on navigational skills

WHERE IN THE BRAIN IS THE HIPPOCAMPUS?

The hippocampus is located in the mid temporal lobe

The role of the hippocampus is to facilitate spatial memory (navigation)

Each hemisphere of the brain has a hippocampus

Hippocampus means seahorse and that’s what its named after!!!

Research Question: Can changes in the brain be detected in those with extensive navigation experience ?

The hypothesis: That the hippocampi in London Taxi drivers

will be structurally different to the hippocampi in non-taxi drivers

‘THE KNOWLEDGE’

What is the ‘The Knowledge’?

http://www.psychexchange.co.uk/videos/view/20331/

What is it? How long does it take? How is it assessed?

METHOD

Experimental Independent measures design Data collection through MRI (magnetic

resonance imaging) scan of brains

INDEPENDENT VARIABLES

Whether subject was a London Black cab taxi driver or not

For correlation, time spent as a taxi driver and size of hippocampus

DEPENDENT VARIABLES

VBM (voxel-based morphometry) identifies grey matter density in MRI scans

Pixel count independent (blind) count of pixels within three

regions of the hippocampus; posterior, body and anterior

PARTICIPANTS

Experimental group16 right-handed, male, licensed London

taxi driversaged range 32–62 years (mean age 44

years)all had licence for at least 1.5 years (range

1.5–42 years, mean 14.3 years)all had healthy medical profiles

control group50 non-taxi drivers, male, right-handed,

controlled for age range and mean age, spread throughout range

PROCEDURE

Structural MRI scans were obtained.

Data measured using two different techniques – voxel-based morphemetry (VBM) and pixel counting.

Voxel-based morphology (VBM) used to measure density (amount) of grey matter in brain. VBM provides 3D measurement of volume of an area.

Pixel counting consists of counting pixels in images provided by the MRI scans. A pixel is simply a 2D measurement of an area. Areas were calculated by taking images of slices of the whole length of the hippocampus. Scan=24 slices of hippocampus area (6=posterior, 12=body & 6=anterior)

The pixel counting was carried out by a researcher who was experienced in this technique and importantly was not aware of the previous VBM results and whether the slices being counted were scans of taxi drivers or controls.

RESULTS

There was significantly more grey matter volume found in the brains of taxi drivers than in the brains of the control group in the right and left hippocampus only (not anywhere else in brain).

This was found only in the posterior hippocampus.

There were no overall differences in pixel count.

Taxi drivers had larger posterior hippocampus but smaller anterior hippocampus – showing no overall differences

CORRELATION

Data was correlated between time as taxi driver and volume of hippocampus.

Positive correlation was found only in right posterior hippocampus.

Negative correlation was found between anterior hippocampus and time spent as a taxi driver.

CONCLUSIONS Taxi drivers had larger posterior hippocampi and

smaller anterior hippocampi.

Correlation suggests this is a result of being a taxi driver, not pre-existing structure which predisposes a person to become a taxi driver.

Nurture rather than nature. So it grew because of being a taxi driver?

CONCLUSION The posterior hippocampus deals with previously

learned information e.g. taxi drivers’ ‘knowledge’ or test they take to become licensed. As this is fine-tuned, the posterior hippocampus becomes larger.

The left hippocampus size does not correlate with the length of time as a taxi driver but the posterior is still higher in taxi drivers, so probably stores memories which don’t require spatial elements e.g. names, faces, and so on.

Brain structures can change depending on input/function.

This plasticity (ability to change and adapt) is useful for rehabilitation of brain-injured patients as it suggests that brain structures can be altered

http://www.youtube.com/watch?v=snO68aJTOpM