Hemispheric Lateralisation & Split-brain research

• 2 PRO of Sperry's split-brain research

  P = used standardised procedures 

  E = was highly controlled to limit any extraneous variables

  T = highly credible 

  
  

  P= supports the idea of hemispheric lateralisation 

  E = e.g. during 'say what u see task' the LH was in control etc 

  T = left and right hemispheres are distinct
• 2 CONS of Sperry's split-brain research

  P = hard to establish causation

  E = behaviour of Sperry split-brain ppts was compared to a group that had no epilepsy = major confounding variable

  T = any differences observed might have been due to epilepsy rather than split brain

  
  

  P = low generalisability

  E = was only done on ppl with epilepsy

  T = can't generalise/extrapolate findings to wider population = not everyone has epilepsy = the results might be different with normal ppl
• 1 CON of hemispheric lateralisation

  P = language may not be restricted to the left hemisphere only

  E = Turk et al discovered a patient who suffered damage to the LH was able to develop the capacity to speak in the right hemisphere 

  T =  language is not just in the left hemisphere = brain is more complex than it is = contradicting lateralisation of the brain
• What did this task (draw task) show:

  ☆ A pic was presented on either the LVF or RVF and ppt was asked to draw it 

  ✔ Drawings were constantly better when drawn by the left hand controlled by the RH 

  ✖ than when drawn by the right hand controlled by the LH

  ↳ despite the ppts being right handed 

  ↳ demonstrates the RH is dominant for drawing

  
• What did this task (tactile) show:

  ☆An image was presented on the left visual field

  ✔ The ppt would pick up the object (from a selection hidden behind a screen) as LVF is linked to RH and ∴ left hand 

  ✔ Left hand also able to select an object that was mostly associated with the object presented (e.g selecting an ashtray when shown a cigarette)

  
• What did this task (say/describe what you see & tactile test ) show:

  ☆ 2 words were presented on either side of the visual field (key to LVF and ring to RVF)

  ✔ The ppt would say RING as RVF is linked to LH which processes language 

  ✖ WILL NOT say key as RH doesn't process language 

  ✔ The ppt would pick up the key as LFV is linked to RH and ∴ left hand 

  
• Sperry's research (procedure)


  •  11 ppl who had a split-brain operation were studied an image/word was projected to the ppts RVF and the same or different image/word was projected to the LVF
  • ↳ which involved a describe what you see task, draw task and tactile task (touching task)
• What happens to the brain during epileptic seizures?

  there is excessive electrical activity travelling from one hemisphere to the other 
• Split-brain operation (include whose mainly used on)

  a surgical operation/procedure involving cutting the corpus collosum in patients with severe epilepsy to reduce the epilepsy

  ↳ allows split brain research
• Split-brain research


  studies how the hemispheres function (lateral function) when they can't communicate with each other after undergoing a 'split-brain' operation
• What is that?

  A) Corpus callosum

  
• Function of the corpus callosum

  connects the left hemisphere and right hemisphere

  ↳ allowing info to be transmitted from one side of the brain to other (from left to right etc.)
• Explain how vision works:

  1. Eye receives light from both right and left visual field (LVF & RVF)
  2. The LVF of both eyes is connected to right hemisphere and the RVF of both eyes is connected to left hemisphere
  3. The info from RVF is processed by LH and the info from LVF is processed by RH
  4. All this is processed in the visual cortex (occipital lobe) at back of brain
  5. This differences in perspective from each eye, enable us to see things in 3D

  
• Label the vision diagram

  A) Left visual field

  B) Right visual field

  C) Right hemisphere

  D) Left hemisphere

  E) Visual cortex (occipital lobe)

  
• What does the right hemisphere control?


  • left side of the body
  • facial recognition 
  • drawing 
  • music
  • spatial task (everyday tasks e.g. brushing hair etc.)
  • spatial task (everyday tasks e.g. brushing hair etc.) etc.)
  • the synthesiser (brings info from both hemispheres together)
  • left visual field = views objects in the left visual field
• What does the left hemisphere control?

  • right side of the body
  • language 
  • analytical tasks 
  • right visual field = views objects in right visual field (things u see on the right side) 
• Localisation vs Lateralisation

  Localisation = specific function is located in a specific area of the brain and is controlled by that area

  Lateralisation = specific function is dominated/controlled by one hemisphere rather than the other
• Hemispheric Lateralisation (with e.g.)

  the idea that one hemisphere dominates a certain function rather than the other = ∴ the 2 halves of the brain (hemispheres) are functionally different

  ↳ language (Broca's and Wernicke's area) is lateralised/controlled/dominated by the left hemisphere
• Lateralisation

  when one side of the body/brain dominates a certain function
• Right hemisphere of brain controls the left-hand side of the body
• Left hemisphere of brain controls the right-hand side of the body
• The brain is split into the right and left hemisphere