Split brain AO1

• Hemispheric lateralisation?


  The idea that two halves of the brain are functionally different and that certain mental processes and behaviours are mainly controlled by one hemisphere. 
• Right side of brain

  • Creative

  Imagination

  Insight

  Facial recognition

  Drawing/writing

  Music awareness
• Left side of brain

  • Language/Speech

  Logic

  Reasoning

  Science/Maths

  Understanding written communication
• Corpus callossum

  Corpus callosum is a bundle of nerve fibres which connect the two hemispheres

  The hemispheres communicate through the corpus callosum
• Commissurotomy?


  division of the two hemispheres by surgery
• Split brain research

  •Studies in 1960s on epileptic patients who had experienced a surgical separation of the hemispheres of the brain (commissurotomy)

  •In a normal brain the corpus callosum would share information across both hemispheres.

  •Split brain patients could not do this which allowed researchers to investigate the extent to which brain function is lateralised.
• Sperry's aim?


  Wanted to examine the extent to which the two hemispheres are specialised for certain functions
• Type of Sperry's study

  Quasi experiment with 11 participants
• Participants in Sperry's study

  Suffered from epilepsy that couldn't be treated with drugs and had already had their corpus calossum split
• Method of Sperry?


  Sperry devised a procedure in which an image or word could be projected to a patient’s right visual (processed by the left hemisphere) and the same, or different image could be projected to a patient’s left visual field (processed by the right hemisphere).
• How did it work?

  The participant gazes at a fixation point on an upright translucent screen

  slides are projected either side of the fixation point (into one visual field or the other) at a rate of one picture per 1/10 second
• What do these show?

  • each hemisphere has completely separate functions
  • left- language
  • right- visual and creativity
• Sperry's variations


  1. describing what you see
  2. recognition by touch
  3. composite words
  4. matching faces
• describing what you see

  When a picture of an object was shown to a patient’s right visual field they could easily describe what was seen

  When a picture was presented to the left field of vision they could not describe it (they often reported that there was nothing there).
• Recognition by touch

  •If patients are shown an object in their left visual field they can pick up the object (from a selection hidden behind a screen) with their left hand.

  •The left hand was also able to select an object most closely associated with the object presented (e.g. select an ashtray when shown a cigarette) to the left visual field.

  •In both cases patient couldn’t verbally identify what they had seen, but could ‘understand’ what the object was
• composite words

  •If two words were presented simultaneously, one on either side of the visual field (for example key to left visual field and ring to the right visual field)

  •Patient would select a key with left hand (left visual field goes to right hemisphere linked to left hand)

  •They would say the word ‘ring’
• matching faces

  •Right hemisphere dominant in terms of recognising faces

  •When asked to match a face from a series of other faces the image in the left visual field (processed by right hemisphere) was consistently selected

  •Picture presented to left hemisphere ignored

  •When a composite image was presented left hemisphere dominated for description & right for selecting a matching picture