localisation of brain function, hemispheric lateralisation

• Corpus callosum


  Connects two hemispheres together

  Aids the two hemispheres to communicate & transfer information between each other
• Hemispheric lateralisation


  Some of our physical and psychological functions are controlled or dominated by a particular hemisphere, eg. left hemisphere; speech comprehension & logical reasoning, right hemisphere; facial recognition & spatial reasoning
• Contra-lateralisation


  When the right hemisphere deals with the left hand side of the body & vice versa
• Localisation of function


  Different areas of the brain are responsible for different functions
• Visual cortex (occipital lobe)


  Receives & processes visual information

  Visual area contains different parts that process different types of information
• Motor cortex (frontal lobe)


  Responsible for voluntary movements by sending signals to the muscles in the body
• Auditory cortex (temporal lobe)


  Analyses & processes acoustic information
• Somatosensory cortex (parietal lobe)


  Receives incoming sensory information from the skin to produce sensations related to pressure, pain , etc
• Frontal lobe


  Area of consciousness, personality, decision making, emotional regulation, include Boca's area &motor cortex
• Damage to frontal lobe


  Changes to personality, impulse control, impaired speech production, impaired movements
• Parietal lobe


  Includes the somatosensory cortex which gets sensations from the skin, also involved in spatial movements
• Damage to parietal lobe


  Humans wouldn't be able to feel sensations or use touch
• Occipital lobe


  Visual cortex & perception
• Damage to occipital lobe


  Problems with vision/perception
• Temporal lobe


  Includes auditory cortex, receives sensory information from the ears, includes Wernicke's area
• Damage to temporal lobe


  Hearing/language issues, can't understand language
• Phineas Gage (support of localisation of function)


  Damage to frontal lobe (pre-frontal cortex) resulted in personality change; become aggressive & impulsive
• Phineas Gage (weaknesses)


  -Low external validity due to uniqueness of this case & the fact it is only one person means it is very difficult to generalise the results that's the frontal lobe is responsible for personality for everyone

  -Lashley: removed 10-50% of the rat's brain and rats had to learn how to get around a maze, no one area was more important than another, used every part of the cortex to learn
• Broca's area


  An area of the frontal lobe in the left hemisphere of the brain responsible for speech production
• Wernicke's area


  An area of the temporal lobe in the left hemisphere responsible for language comprehension
• Issues with Broca's area

  -No brain scanning at the time so unsure if the damaged part was responsible for impaired language function

  -The brain has now been scanned & more brain damaged was found

  -More recent case studies of stroke victims & the use of fMRI's has shown that Broca's is responsible for language production
• Wernicke's area case study

  -Case study of stroke patient who could not comprehend what was being said to him

  -Post mortem when he died showed lesion to rear temporal lobe on left hemisphere

  -Responsible for language comprehension
• Damage to Wernicke's area

  -Comprehension issues

  -Can't understand language

  -May make up words
• Sperry: Split brain results


  Left hemisphere is responsible for language production, ppts could verbally describe what they felt & could identify the object given to their right hand

  Right hemisphere is superior when it comes to visual motor tasks & when object is placed in ppt's left hand they couldn't describe what they felt
• Sperry: Split brain conclusion


  Left hemisphere responsible for verbal & reasoning tasks, the left is the 'analyser'

  Right hemisphere responsible for spatial tasks & facial recognition, the right is the 'synthesizer'

  There is a duality in that each hemisphere works in isolation forming independent thoughts & consciousness only being more apparent
• Strengths of Sperry's split brain study

  Lab experiment: high internal validity, well controlled procedure, ppts blindfolded in eye they weren't meant to be using so we can be certain they were only presented with left/right field of vision
• Weaknesses of Sperry's split brain study

  -Low ecological validity: in real world, ppts would have use of both eyes

  -Small unique sample: limits generalisations, only 11 ppts who had neuro-surgery in order to separate the two hemispheres of the brain

  -All ppts have been epilepsy sufferers which may have caused structural damage to the brain

  -No control group was used, so can't make comparisons
• Lashley: Rat study


  Researched rat's brains to find specific areas for learning

  Rats had to learn to get around a maze

  10-50% of the rat's brain were removed & they were tested again

  Rats could still learn to get out of the maze

  Supports holistic theory that learning it too complex to be localised in just one part of the brain
• Issues with Lashley's Rat study

  Brain damaged rats running in a maze can't easily be generalised to humans as we may experience brain damage & cognitive impairment differently
• Localisation of function

  Areas of the brain

  A) frontal lobe

  B) somatomotor cortex

  C) somatosensory cortex

  D) parietal lobe

  E) occipital lobe

  F) cerebellum

  G) Broca's area

  H) Wernicke's area

  I) temporal lobe