Both Ao1 and Ao3 content for hemispheric lateralisation and split-brain research, including Sperry (1968). Part of AQA A-Level Psychology, Biopsychology topic.
Hemispheric lateralisation:
Ao1:
The idea that the two hemispheres of the brain are functionally different and that certain
functions (e.g. language) are the responsibility of one hemisphere but not the other.
The 2 hemispheres are connected by a set of nerve fibres called the corpus callosum.
- These fibres facilitate the communication between the left and right hemispheres of
the brain.
Ao3:
+ Evidence to support: Sperry + Gazzaniga (1967) split brain research
- Studied patients who had undergone surgical procedure to treat epilepsy in
which the corpus callosum connecting the 2 hemispheres was severed.
- When patients were presented with an image to their right visual field the
patients could describe what they saw in words.
- This is because information from the right visual field is processed by the left
hemisphere, which can comprehend language.
- When the image was presented to the left visual field, patients would say they
saw nothing.
- This is because information from the left visual field is processed by the right
hemisphere, which cannot comprehend language.
- Supports concept of hemispheric lateralisation as shows that certain functions
like language are dominant to the left hemisphere.
- Contradictory evidence: Turk et al. (2002)
- Found evidence of the right hemisphere’s ability to process and produce
speech.
- Patient (JW) suffered damage to the left hemisphere but developed the
capacity to speak from the right hemisphere
- eventually leading to the ability to speak about the information presented to
either side of the brain.
- Shows the brain has the ability to adapt significantly following brain damage
(neuroplasticity).
- Contradicts idea that certain functions such as language can only be
performed by 1 hemisphere, in this case the left hemisphere.
- Lateralisation of function changes with age: Szflarski et al. (2006)
- Found that language becomes more lateralised to the left hemisphere until
the age of 25, at which point lateralisation starts to decrease.
- As we age, the brain may allocate tasks to different regions to compensate for
declining functional abilities.
- Contradicts idea that certain functions are performed by 1 hemisphere and
not the other.
- Gender differences in lateralisation: Shaywitz et al. (1995)
- Found that the male brain may be more lateralised for language than females
- Both of these pieces of research show we must also consider the extent to
which the brain is lateralised in different individuals.
Overall, concept of hemispheric lateralisation may be more complex than initially
thought.
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