Laterisation and Split Brain Research

• Hemispheric Lateralisation


  Some of our physical and psychological functions are controlled or dominated by a particular hemisphere.

  E.g. specialized areas for language found in the left hemisphere, and for creativity and visual motor tasks, found in the right hemisphere.
• Sperry (1968)


  Split-Brain Research into whether neural processes may be organized based on the hemispheres in a series of experiments:

  - Visual Fields (drawing)

  - Visual Tasks (screen)

  - Tactile (touching)
• Sperry's Participants


  - 11 participants

  - All undergone a commissurotomy

  - All had epilepsy

  - All had their surgeries at varying times: longest was 5 1/2 years before the study.
• could

  When word or image was presented to the right-visual field, they could describe the information.
• could not

  When word or image was presented to the left-visual-field, they could not describe the information.
• could

  When an object was placed on the right-hand for identification, they could describe the item.
• could not

  When an object was placed on the left-hand for identification, they could not describe the item.
• the hemispheres are not corresponding


  When two different objects were placed in each hand and then hidden for retrieval each hand searches for its own object but if the left-hand picks up the object which the right hand is looking for, the object is rejected but the other hand continues to search because...
• Left hemisphere is responsible for….


  Speech and Language
• Right hemisphere is responsible for…


  Visual-Spatial Processing
• Support for Hemispheric Lateralisation:

  Any of Sperry's (1968) findings
• Support for Hemispheric Lateralisation: Further Evidence

  Architects and the mathematically gifted tend to have superior right-hemispheric skills but are also more likely to be left-handed and to suffer higher rates of allergies and problems with the immune system. E.g. Tonnessen found a small but significant relationship between handedness and immune disorders.Suggests that the same genetic processes leading to lateralization may also affect the development of the immune system
• Weakness of Hemispheric Lateralisation: Sample

  
  

  They all had epilepsy - what if that is causing the hemispheric lateralization? Sample size was too small, varying times of surgeries could be an extraneous variable
• Support for Hemispheric Lateralisation: Methodology

  Ethical: Natural /Quasi-Experiment
• Weakness of Hemispheric Lateralisation: Brain Plasticity


  Brain plasticity contradicts lateralization as you would expect the brain to take on the role of the damaged half.