hemispheric lateralisation

• Hemispheric Lateralisation

  The idea that the two halves of the brain are functionally different and that each hemisphere has functional specialisations, e.g. the left is dominant for language, and the right excels at visual motor tasks

  
• Corpus Callosum


  Nerve fibres that connect the two hemispheres and facilitate interhemispheric communication, allowing the left and right hemisphere to 'talk to' one another
• Split brain patients are individuals who have undergone a commissurotomy

  
• Aim of Sperry and Gazzaniga's research

  To examine the extent to which the two hemispheres are specialised for certain functions
• Sperry and Gazzaniga's experiments

  1. Describe what you see

  2. Tactile test

  3. Drawing task
• Language is dominant in the left hemisphere
• Picture presented to the left visual field (processed by right hemisphere)

  Patient could not describe what was shown and often reported that nothing was present
• Picture presented to the right visual field (processed by left hemisphere)


  Patient could describe what they saw, demonstrating the superiority of the left hemisphere when it comes to language production

  
• Object placed in the patient's left hand (processed by the right hemisphere)


  Patient could not describe what they felt and could only make wild guesses, but the left hand could identify the object
• Object placed in the patient's right hand (processed by the left hemisphere)


  Patient could describe verbally what they felt and could also identify the object
• The left-hand (controlled by the right hemisphere) would consistently draw clearer and better pictures than the right-hand, demonstrating the superiority of the right hemisphere when it comes to visual motor tasks
• While the right-hand would attempt to draw a picture, the picture was never as clear as the left hand, again demonstrating the superiority of the right hemisphere for visual motor tasks
• Sperry and Gazzaniga only examined 11 patients, all of whom suffered from epilepsy
• Turk et al. (2002) discovered a patient (J.W.) that suffered damage to the left hemisphere but developed the capacity to speak in the right hemisphere
• Rogers et al. (2004) found that in a domestic chicken, brain lateralisation is associated with an enhanced ability to perform two tasks simultaneously (finding food and being vigilant for predators)