Split brain research

• Split brain research - the chance the investigate the different abilities of the two hemispheres came about in a treatment for severe epilepsy.

  Surgeons cut the corpus callosum in order to prevent the violent electrical activity of a seizure from passing across the hemispheres.

  Patients who underwent this surgery are referred to as split brain patients
• Corpus callosum - connecting bundle of nerve fibres. This allows information received by one hemisphere to be sent to the other hemisphere.
• Split brain - procedure

  Sperry would ask participant to sit in front of a screen and stare at a dot or cross in the middle. An image or word would be projected to a patients right visual field and the same image would be projected into the left visual field. The participant would be asked to report, draw or pick up an object of what they had seen
• Study type 1 - describing what you see

  When a picture of an object was shown to the partners right visual field the patient could easily describe what was seen.

  However if it was shown in the left visual field the patient could not describe what was seen.

  Indicates language centres are in the left hemisphere. Lack of language centres in the right hemisphere
• Study type 2 - recognition by touch

  Even though patients could not verbalise what they've seen, patients could select a matching object from a grab bag using their left hand to match with the object they've seen.

  The patient could not verbalise the object but could understand what the object was.
• Study type 3 - composite words

  If two words were presented simultaneously one on either side of the visual field such as 'key' shown on the left field and 'ring' on the right, the patient would write with their left hand the word key and say the word ring.

  This was because there are no language centres in the right hemisphere, so seeing the word key in the left visual centre they couldn't verbalise that.

  As there are language centres in the left hemisphere, this allowed the patient to verbalise the word shown in the right visual field.
• Evaluation - strengths

  High control - used scientific experiments that were designed to test lateralisation in a highly controlled manner. Meaning the findings would have been objective and more valid.

  Contributed to a greater understanding of brain processes, that the left hemisphere was the analyser and the right was the synthesiser
• Evaluation - weaknesses

  Issues with generalisation:

  • Only 11 participants took part whom all had a history of epilepsy. This may have caused unique changes in the brain which may have affected the findings
  • Some participants have more disconnection of the hemisphere as part of their procedure than others which could have made the findings different
  • The participants were all right handed, left hemisphere dominant for language. Can't be generalised to left handed people