Lateralisation

• What is lateralisation?

  The idea that the two hemispheres of the brain are functionally different & that certain mental processes & behaviours are mainly controlled by one hemisphere rather than the other

  E.g. Language is lateralised- Broca & Wernicke’s area are only in the left hemisphere
• What is split brain research?

  A series of studies that began in the 1960s

  They involved epileptic patents who had a surgical separation of the hemispheres- an operation to cut the corpus callosuum (commissorotomy)

  It allows the researchers to investigate lateralisation
• What is the study that goes with Lateralisation?

  11 split brain patients studies

  • Ppts were asked to look at a dot in the middle of a screen
  • A word/ image was flashed o te screen to either the LVF or RVF for 0.1s

  Presenting the word/ image to one hemisphere meant that information could not be conveyed from that hemisphere to the other
• What was the findings from the study to go with lateralisation?

  When the word/ image was flashed to the RVF it wet to the left hemisphere.

  Ppts could name what they see- speech and language is in left hemisphere (Broca & Wernicke’s area)

  If word/ image was flashed to LVF it went t the right hemisphere.

  Ppts could not name what it was- no speech/ language on right- BUT they could draw it

  Demonstrates that some functions are lateralised

  E.g. LH= verbal, RH= Emotional
• What are the strengths of split-brain research?

  Shows lateralised brain functions

  Left hemisphere= analytical & verbal

  Right hemisphere= adept at spatial tasks and music

  Right hemisphere= Produce basic words & phrases but contributes emotional content to language

  CP- The distinction may be too simplified. Several tasks associated with one hemisphere can also be carried out buy the other

  Methodology that Sperry used:

  Standardised procedure.

  Describe study
• What are the weaknesses of split brain research into hemispheric lateralisation? (G)

  Generalisation

  Findings cannot be widely accepted- split-brain patient are an unusual sample of people

  Only 11 patients took part- all had a history of seizures (may’ve caused changes in brain that influenced findings)

  Reduces validity of conclusions
• What is the weakness of split-brain research into hemispheric lateralisation? (D)

  Differences in hemispheric functions may be overstated

  Oversimplification & overstates the differences between 2 hemispheres

  Distinctions ret clear-cut- behaviours said to be performed by one can be performed by other in some situations

  Flexibility of the 2 hemisphere- Sperry- too simplistic