lateralisation

• what does the left hemisphere of the brain control?

  • speech, language and comprehension
  • analysis and calculations
  • time and sequencing
  • recognition of words, letters and numbers
• what does the right hemisphere of the brain control?

  • creativity
  • spatial ability
  • context
  • recognition of faces
• what fibres connect the two hemispheres of the brain?

  Corpus callosum
• what happened for patients to be in split brain research?

  their corpus callosum had been severed in a surgical procedure which had been done to stop epileptic fits
• what was done in split brain research?

  they sent visual information to just one hemisphere at a time in order to study hemisphere lateralisation
• what is the method of split brain research?

  • experimental situation - split visual field
  • stimulus - visual such as faces
  • task for patient - visuospatial response such as drawing seen item or verbally such as to speak seen item
• what was the process of Sperry's split brain research?

  • patient would fixate on a dot in the centre of the screen while information was presented to either left or right visual field
  • when the person is shown something only visible in the left visual field it is transferred to the right hemisphere
• what has split brain research shown?

  • the brain isn't split into specific sections which deal with specific tasks
  • instead the way the brain is connected between different regions is just as important as the function of the different regions of the brain
• what is an advantage of hemispheric lateralisation?

  • Rogers - found domestic chickens showed enhanced ability to perform 2 tasks at the same time, this suggests lateralisation enhances brain efficiency in cognitive tasks that demand simultaneous but different use of both hemispheres
• evaluation:

  positives and negatives - mathmeticians and architects have been found to be more likely left-hand dominated and have superior right hemispheres but prone to immune system problems - TONNESSEN found a relationship
• evaluation:

  lateralisation changes with age -

  • Szaflarski found that language became more lateralised to the left hemisphere with increasing age in children but after the age of 25 it decreased with each decade
• evaluation:

  language may not be restricted to the left hemisphere

  • Gazzaniga - suggests that some of the early discoveries from split brain research have been disconfirmed by recent discoveries
  • Turk - case of JW a split brain patient who developed the capacity to speak out of the right hemisphere
• methodological evaluation

  • sperry's research was very well designed and employed well through standardised procedures
• methodological problems - sperry

  • the disconnection between the hemispheres was greater in some patients than others
  • some patients had experienced drug therapy for much longer than others
  • data was artificially produced
• what is lateralisation?


  The specialisation of brain functions in the left and right hemispheres.