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Background & Aim

  • The aim is to investigate the effects of having the two hemispheres of the brain 'deconnected' (by cutting the corpus callosum) to control for severe epilepsy.
  • And to describe the different functions of the two hemispheres.
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Method, Procedure & Controls

  • 11 split brain patients, that is, they were patients who had undergone disconnection of the cerebral hemispheres.
  • This was because they had a history of advanced epilepsy which could not be controlled by medications.

Visual Tests

  • Stimulus was presented to one or both visual fields for 1/10th second - too quick for eye movement and so information is presented to one hemisphere only.
  • Hands and objects were kept out of sight.
  • Participants asked to name/identify the word/picture.

Tactile Tests

  • An object presented to either the right or left hand.
  • Different objects put in different hands.
  • One hand touched or put into postition.
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  • When participants were presented with an image in one half of their visual field and then presented with the same image in the other half of the visual field they responded as if they had never seen the image before.
  • If the same image was presented in the original visual field the participants were able to recognise the image as one they had seen before.
  • Participants were not able to give a description of an image that was presented to the left hand side of the visual field.
  • The image was either not noticed or just appeared as a flash.
  • Although they could respond non-verbally by pointing with their left hand to a matching picture or selecting an object presented among a collection of other pictures and objects.
  • If 2 symbols were presented simultaneously, one on either side of the visual field (eg. a dollar sign on the left and a question mark on the right) and the participant was required to draw with their left hand (shielded from their own view) what they had seen, they would draw the left visual field symbol (a dollar sign).
  • If they were required to say what they had just drawn, the participant would say by name, the right visual field symbol (a question mark).
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Results (2)

  • Objects put in the participants hand for identification by touch could be described or named in speech or writing if they were in the right hand but if placed in the left hand, the participant could either only make wild guesses or even appeared to be unaware that anything at all was present.
  • However, if the object was taken from the left hand and placed in a 'grab bag', or was scrambled among other test items, the participant was able to search out and retrieve it with their left hand.
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Conclusions & Implications

  • Sperry argues that his studies give considerable support to his argument of lateralisation of function.
  • That is, that different areas of the brain specialise on different tasks, such as the left hand side being responsible for language.
  • The right hemisphere is superior in drawing spatial relationships.
  • He also went on to argue that each hemisphere has its own perceptions and memories and experiences.
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