Lateralisation

• What side of the hemisphere controls the left side of the body?

  Right hemisphere
• What side of the hemisphere controls the right side of the body?

  Left hemisphere
• How is the sensory information on one side of the body received?

  It is received by the hemisphere on the opposite side of the brain
• What does lateralisation of brain function mean?

  There are certain mental processes that are mainly specialised to one side or the other
• What did split brain patients go through?

  Surgery to cut the corpus callosum, the main bundle of neuronal fibres connecting the two sides of the brain
• Where does information we see travel through?

  Our left and right visual fields
• What did Sperry make split brain patients do in his experiment and what were his findings?

  • A word is flashed briefly to the right field of view, and the patient is asked what he saw, because the left hemisphere is dominant for verbal processing, the patient's answer matches the word
  • Then, a word is flashed to the left field of view, and the patient is asked what he saw, because the right hemisphere cannot share information with the left, the patient is unable to say what he saw, but instead he can draw it
• What are Sperry's conclusions about lateralisation?

  There are differences between the hemispheres, the left hemisphere is responsible for speech and language, the right hemisphere is responsible for face recognition
• How did Sperry find that the right hemisphere is responsible for face recognition?

  He showed split brain patients faces made of fruits used, when it was showed to the left visual field, patients recognised a face. However when it was showed to the right visual field, patients could only see fruits.
• Why can't Sperry's findings be generalised?

  Because the split brain experiment was based on 11 patients with epileptic seizures -> Unique brain changes may have influenced findings, therefore may not apply to 'healthy patients'
• Why may the difference between the hemispheres be exaggerated?

  Modern neuroscientists would say the the brain is much less clear cut than suggested in this study, 'verbal' and 'non verbal' labels only apply on occasion, brain function is much more messy -> the hemispheres can perform the other hemisphere's tasks when required suggest the theory is inaccurate
• What is a strength of Sperry's research

  Use of standardised procedures allowed him to have high controls and vary aspects of the basic procedure -> provides validity to the results and allows it to be easily replicated
• How has Sperry further demonstrated lateralisation?

  Further research had shown the left hemisphere to control speech and language, whereas the right side controls visual information, indicating that different sides of the brain perform different functions

  -> However, later research contradicts this, limiting the validity of the study
• How did Gazzinga (1998) challenge the claim that language is restricted to the left hemisphere?

  Split brain patient case study with capacity to speak out of the right hemisphere, could then speak about information presented to the left or right of the brain, despite damage to the left hemisphere -> contradicts theory as the brain has plasticity, showing the theory is too simplistic
• What advantages did Tonnessan (1993) suggest about hemispheric lateralisation?

  Found in domestic chickens, lateralisation is associated with an enhanced ability to perform tasks simultaneously, finding food and being vigilant for predators -> lateralisation aids brain efficiency in cognitive tasks, an advantageous characteristic for survival