Localisation of function

• Phineas Gage (1848)

  an explosion occurred leaving Phineas Gage with a metre long metal pole through his left cheek, behind his eye and exiting at the top of his head

  gages personality changed dramtically
• Left Hemisphere


  controls the right side of the body; analytical, language, math
• Right Hemisphere


  controls the left side of the body; creative, intuitive, spacial
• Broca's Area


  Controls language expression - an area of the frontal lobe, usually in the left hemisphere, that directs the muscle movements involved in speech.
• Wernicke's Area


  controls language reception - a brain area involved in language comprehension and expression; usually in the left temporal lobe
• Frontal Lobe


  Lobe of the brain which has executive functions, thinking planning and organisation
• Motor Cortex


  controls voluntary movements
• Parietal Lobe


  allows the individual to understand interactions with the world

  aids in learning of complex, precise movement (e.g. writing)
• Occipital Lobe


  allows the individual to see and understand visual information
• Temporal Lobe


  allows the individual to hear and comprehend auditory information

  aids in memory and spatial navigation (hippocampus)
• Sperry research method

  Quasi experiment

  IV naturally occuring - corpus callosum severed or not

  DV - performance in visual and tactile tasks
• Sperry sample

  11 split brain participants who had their corpus callosum severed.

  All had the operation because of severe epilepsy.

  9 had recently undergone the surgery.
• Sampling method- Sperry

  Opportunity sampling

  Tool those who have had their corpus callosum severed and were willing to take part.
• Sperry equipment

  A tachistoscope

  Information presented on a screen from a projector behind it.

  Objects given under the screen where they could not see their hands.
• Sperry controls

  - All materials for the visual and tactile tasks kept the same

  - All tested individually and had to remain silent unless asked a question

  - All visual material was presented to either the LVF or RVF for 1/10 second
• Sperry experiment - Objects were presented in the right visual field

  Information went to left hemisphere.

  Participants could say what they saw, describe it in speach or writing.

  Find it with their right hand from an array of objects.
• Sperry experiment - Objects were presented in the left visual field

  Information went to the right hemisphere.

  Participants could draw the object with their left hand.

  Couldn't say that they saw anything.
• Sperry experiment - Different visual stimuli presented simultaneously in each field

  Could draw the object in RVF with their left hand but couldnt say they saw it.

  Could name the object in LVF.

  After drawing object from RVF, would say that they have drawn the object in LVF.
• Sperry experiment - Simple mathematic problems were presented to the left visual field

  Information went to right hemisphere.

  Participants could work out the problems
• Sperry experiment - A nude pin-up was presented to the left visual field

  Information went to the right hemisphere.

  Participants blushed and giggled - they couldnt say why they did this.
• Sperry experiment - Objects were felt by the right hand

  Information went to the left hemisphere.

  Participants could identify the object by name
• Sperry experiment - Objects were felt by the left hand

  Information went to the right hemisphere.

  Participants could point to the object or find it again with left hand.

  They had no concious awareness of it and couldnt say what is was or describe it.
• Sperry Conclusions

  Left hemisphere controls language.

  Right hemisphere controls drawing, maths, emotions but doesn't control lanuage.
• Sperry experiment - Ethics

  Upheld:

  • Informed consent
  • No deception
  • Protection from physical harm
  • Right to withdraw

  Broken:

  • Participants now aware that they had a disability: psychological harm
  • Repetition of tasks may have been stressful: psychological harm
• Sperry reliability evaluation

  Internal: Many controls ensuring a standardised procedure and replicability

  External: General trends found in the lateralisation in brain function in the split brain participants but there were some outright exceptions. Sample not large enough.
• Sperry validity evaluation

  Internal: The differences could have been due to their previous epilepsy or the medication they had been taking so brain function may have been different anyway.

  Population: Can't be generalised to the 'normal' brain as the sample was atypical but could be generalised to other split brain patients.

  Ecological: So little people have a severed corpus callosum so not likely to be reproduced in real life - people are also not likely to only have to receive information with one eye. Tactile tasks are more ecologically valid.
• Sperry experiment - Ethnocentrism

  Is ethnocentric, only done in America - our environment and culture infuences how our brain develops so participants brought up in other envrionments may differ in brain lateralisation.
• Sperry experiment - Link to biological area

  Investigating regions of the brain and lateralisation of brain function, specifically demonstrating the importance of the corpus collosum as a communication pathway between hemispheres and provided evidence for the functions each hemisphere performs.
• Sperry experiment - Link to key theme

  As well as holding the two hemispheres together, the importance of the corpus collosum as a pathway of communication is made evident . The tasks that the split brain participants could not perform presented no difficulties for the control group as their corpus collosum was still intact so the hemispheres could still communicate.
• Sperry experiment - Link to psychology as a science

  Carried out in controlled lab conditions which fufills scientific criteria.

  Possible to be proven false however would need more split brain participants which is not possible.
• Sperry experiment - Link to usefullness of research

  Begining to understand the physiognomy of the brain and how it works.

  Revealed the importance of the corpus callosum as a pathway for internal communication between the two hemispheres.

  Limited usefullness through small atypical sample.
• Sperry aims

  To study the functions of seperated and independant hemispheres specifically to see the effects of hemisphere disconnection in split brain patients who have had their corpus collosum severed