Split-Brain Research into Hemispheric Lateralisation

• What is lateralisation in the brain?

  Certain functions are governed by one side
• What is the primary role of the left hemisphere?

  It is considered the analyser
• What is the primary role of the right hemisphere?

  It is considered the synthesiser
• What does contralateral mean in relation to the brain?

  Controls opposite sides of the body
• Which hemisphere is connected to the left visual field?

  The right hemisphere
• Which hemisphere is connected to the right visual field?

  The left hemisphere
• What did Fink et al (1996) discover about visual processing in the brain?

  • Right hemisphere active for global elements
  • Left hemisphere active for finer details
• What does the research suggest about hemispheric lateralisation in the connected brain?

  It is a feature of both connected and split brains
• What does research suggest about brain dominance and personality?

  No evidence of a dominant side affecting personality
• What did Nielsen et al (2013) find regarding brain hemisphere usage?

  No evidence of a dominant side
• What happens during an epileptic seizure in the brain?

  Excessive electrical activity travels between hemispheres
• What is a corpus callosotomy?

  Cutting the corpus callosum to reduce seizures
• What is the outcome for split-brain patients after a corpus callosotomy?

  Few side effects and significant relief from epilepsy
• What was the aim of Sperry's (1968) study?

  • Investigate effects of hemisphere deconnection
  • Show different functions of each hemisphere
• What was the procedure in Sperry's (1968) study?

  • 11 split-brain participants
  • Control group with no disconnection
  • Images projected to right and left visual fields
• What were the findings when an image was shown to the right visual field?

  Participants could describe what they saw
• What were the findings when an image was shown to the left visual field?

  Participants could not describe it but could select a matching object
• What did Luck et al (1989) find about split-brain participants?

  • They perform better on certain tasks
  • Faster at identifying odd one out
  • Left hemisphere strategies are less effective in normal brains
• What is a major confounding variable in Sperry's study?

  Participants in control group had no epilepsy
• What does the confounding variable imply about the findings?

  Differences may be due to epilepsy, not split brain
• What is a strength for Lateralisation?

  • Lateralisation in the Connected Brain
  • Fink et al (1996) used PET scans to identify which brain areas were active during a visual processing task
  • When participants were asked to attend to global elements of an image, regions of the right hemisphere were much more active and when required to focus in on finer detail, specific areas of the left hemisphere tended to dominate
  • This suggests that, at least as far as visual processing is concerned, hemispheric lateralisation is a feature of the connected brain as well as the split brain
• What is a limitation for Lateralisation?

  • One Brain
  • There might be different functions in the right hemisphere and the left hemisphere, but research suggests people do not have a dominant side of their brain which creates a different personality
  • Nielsen et al (2013) analysed brain scans from over 1000 people aged 7 - 29 years old and did find that people used certain hemispheres for certain tasks, but there was no evidence of a dominant side
  • This suggests that the notion of right-brained or left-brained people is wrong
• What is a strength for Split-Brain research into Hemispheric Lateralisation?

  • Research Support
  • Luck et al (1989) showed that split-brain participants perform better than connected controls on certain tasks
  • For example, they were faster at identifying the odd one out in an array of similar objects than normal controls, while in the normal brain, the left hemisphere‘s better cognitive strategies are ‘watered down’ by the right hemisphere
  • This supports Sperry’s earlier findings that the ‘left brain’ and the ‘right brain’ are distinct
• What is a limitation for Split-Brain research into Hemispheric Lateralisation?

  • Generalisation Issues
  • The behaviour of Sperry’s split-brain participants was compared to a neurotypical control group, however none of the participants in the control group had epilepsy
  • This is a major confounding variable, as any differences that were observed between the 2 groups may be the result of the epilepsy rather than the split brain
  • This means that some of the unique features of split-brain participants’ cognitive abilities might have been due to their epilepsy