Localisation of Brain Function (A2 only)

Q: Sperry (1968) — Effects of Split-Brain Surgery

**Sperry (1968)** investigated lateralisation of brain function in split-brain patients.

Q: Maguire et al (2000) - Evidence for Plasticity

**Maguire et al (2000)** studied London taxi drivers to discover whether changes in the brain could be detected as a result of their extensive navigational experience.

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Plasticity and Functional Recovery of the Brain After Trauma

The brain has the incredible feature of being able to alter both its structure and function. This is known as plasticity. Plasticity is important for learning and for recovery after trauma.

Plasticity

Plasticity works through four main principles:
- Impulses travel along neurons and travel to the next neuron via a synapse.
- Neural pathways are created as new information is passed from one neuron to another.
- The more these neural pathways are used, the stronger the pathway becomes.
- If the pathway is not used regularly, the connection weakens.

Plasticity and age

Plasticity happens not only in babies and children, but in adults as well.
Adults who have had brain damage have been able to recover the loss of function.

Functional recovery after trauma

The brain can be damaged in several ways: stroke, injuries, tumours and infections.
Because of plasticity, the brain can rewire and reorganise itself.
For example, if a stroke patient has damage to the area of the brain that controls the left hand, then healthy areas around the damaged part can take over that function.

Sperry (1968) — Effects of Split-Brain Surgery

Sperry (1968) investigated lateralisation of brain function in split-brain patients.

Research method

A natural experiment (participants had already had their corpus callosum severed due to severe epilepsy).
There were 11 participants (10 men and 1 woman).
Participants took a range of visual and tactile tests.
- In the visual tests, images were flashed into their left or right visual field for a 1/10 of a second and they were asked to name, describe or draw the objects.
- In the tactile test, objects were placed in either their left or right hand behind a screen.

Research findings

Information presented to the right visual field could be described in speech and writing. If the same information was presented to the left visual field, the participant could not remember seeing anything and could not describe it.
Objects placed in the right hand could be described in speech or writing. If the same objects were placed in the left-hand, participants guessed and sometimes seemed unaware they were holding anything.

Research conclusion

These findings support the theory that for right handed people, language is processed in the left hemisphere of the brain.

Evaluation of Sperry (1968)

Strengths
- Controlled and standardised - reliable.
Limitations
- Small sample.
- Individual differences.
- Lack ecological validity.

Maguire et al (2000) - Evidence for Plasticity

Maguire et al (2000) studied London taxi drivers to discover whether changes in the brain could be detected as a result of their extensive navigational experience.

Procedure

A natural experiment.
Using an MRI scanner, the researchers calculated the amount of grey matter in the brains of taxi drivers and a set of control participants.

Results & conclusions

Results
- The posterior hippocampi of taxi drivers were significantly larger relative to those of controls and posterior hippocampal volume was positively correlated with the amount of time they had spent taxi driving.
Conclusion
- This demonstrates brain plasticity. The structure of the brain can change in response to the demands placed upon it.