Lateralisation and Split Brain Research

• The brain

  • the two halves of the brain are functionally different and certain processes or behaviours are controlled by one hemisphere
  • the right side of the brain processes information from the left half of the body (language)
  • the right side of the brain processes information from right half of the body (face recognition, drawing ability, spatial tasls)
• Split Brain Patients

  • a group of patients who had a corpus callosotomy
  • where the corpus callosum is severed so that the two hemispheres are separated and don't communicate with each other
  • this was done to control frequent and severe epileptic fits
• Sperry (1968)

  • investigated what functions of the brain are lateralised
  • compared split brain patients to others with no hemisphere separation different activities were tried with the patients including touch of objects and visual representation of stimuli
  • if a patient was shown something to their left visual field, they wouldn't be able to verbalise what it is
  • if a patient was shown something to their right visual field, they would be able to say what it is
• Touch

  • if a patient was shown an object in their left visual field, they would be able to select that object from a range of others, with their left hand
  • if a patient was shown an object in their left visual field, they wouldn't be able to select the object with their right hand
  • if they were holding objects in different hands and told to pick it up, the left one world be able to pick it up whilst the right hand will pick up random things
• Drawing

  • a picture is shown to the left or the right visual field and the patient is then asked to draw it
  • the drawing were consistently better when drawn by the left hand (controlled by the right hemisphere), despite the patients actually being right handed
  • this suggests that the right hemisphere was superior at drawing ability
• Composite words

  • if a patient was shown two different words to their left and right visual field, they would say what is processed by the left hemisphere and would pick up what was processed by the right hemisphere with their left hand
• Face Recognition

  • if their was a split view of a man and a woman (on the right) and they had to name it, they would be likely to say man as they man side of the face is processed by the left hemisphere as the left deals with language
  • if they saw the same picture and were asked to pick out the same photo and a matching photo of what they've seen they'd select an image of the woman as it is processed by the right hemisphere
• Conclusions

  • it seems that in these patients the hemispheres of the brain process information separately
  • hemispheres do have differing functions (e.g. language left and drawing ability right)
  • patients seem to have separate streams of consciousness with their own memories and perceptions