Lateralization and Split Brain

• What is Hemispheric Lateralisation?

  - Two hemispheres are not exactly the same, each has its own functional specialisations

  - Left is dominant for language and speech, right for visual-motor tasks

  - Hemispheres connected by nerve fibres called corpus callosum allowing interacting and transfer of info
• What is Split-Brain Research?

  - When the bundle of fibres making the corpus callosum are cut, the connection between the 2 hemispheres is severed

  - This allows the investigation of the different abilities of the separate hemispheres
• Describe Sperry and Gazzaniga's Research

  A: To investigate the different abilities of the hemispheres

  P: A picture/word is flashed up on a screen in either the patient's right or left visual field.

  F: When pic was flashed in the right visual field, patient could easily describe what they saw. Same object on the left, couldn't be described/seen → This is because our language centre is in the LEFT hemisphere (remember that what is seen in the left visual field, goes to the right hemisphere &vice versa)

  ○ However, patients could physically select an object projected in the left visual field using their left hand though unable to verbally identify → Visual-motor tasks centre in RIGHT hemisphere

  ○ If two words simultaneously presented, patient would write w/left hand what they saw in their left visual field, and say the word in their right visual field

  C: Left hemisphere responsible for speech and language and right hemisphere in visual-spatial processing and facial recognition
• Evaluate Hemispheric Lateralisation


  ✓ Increases neural processing capacity, allows multi-tasking as each hemisphere will engage in separate functions → Rogers, domestic chicken, brain lateralisation allowed enhanced ability to finding food while being vigilant for predators

  ✓ Architects and the mathematically gifted tend to have superior right-hemispheric skills

  ✗ Changes with age, Szaflarski found lang became more lateralised to left HS w/increasing age, after 25 decreases with each decade of life
• Evaluate Split-Brain Research


  ✓ Started initial understanding, built foundation of understanding brain and how hemispheres work

  ✗ Gazzanga suggests early discovered have been disconfirmed → JW developed capacity to speak out of right HS, able to speak about info presented to left/right brain

  ✗ Rarely carried out today → Hard to generalise info due to confounding disorders of such case studies