Lateralisation

• What is lateralisation?


  The idea that certain mental processes are controlled by a specific hemisphere
• What part of the brain allows communication between hemispheres?

  Corpus callosum
• How do we research lateralisation?

  Split brain research
• What are split brain patients?

  Those with their corpus callosum cut
• What did Sperry do?

  Presented information to either the right visual field or left visual field of patients, who had to respond with either their right or left hand, or verbally
• What did Sperry find?


  When a picture was presented to the right visual field the patient could describe it but not draw it

  When a picture was presented to the left visual field, the patient could draw it but not describe it
• Which hemisphere is language localised to?

  Left
• What is the right hemisphere involved in?

  Visuospatial processing
• What is some contrasting evidence for lateralisation?

  Turk et al (2002) - patient JW could speak information presented to both hemispheres
• What is good about Sperry’s research?

  Highly controlled and specific
• What are some issues with lateralisation research?

  • Research based on patients with atypical brains, so it is unrepresentative
  • Limited samples, not may have split brains as they are only when all other treatments for epilepsy have failed
• What are the factors affecting lateralisation?

  Gender

  Age

  Handedness
• How does gender affect lateralisation?

  Women are more bilateral so recover faster from brain damage
• How does age affect lateralisation?

  Szafalski et al (2006) - found language became more lateralised to left hemisphere with age
• How does handedness affect lateralisation?

  More bilateral if left handed (75% in left hemisphere compard to 95% in right handed people)