localisation of function

• define localisation of function

  theory that specific brain regions control specific functions
• outline the work of Penfield on localisation of function

  discovered electrical stimulation of brain which produced different responses

  • movements and memory recall depended on the location
  • "mapped" body parts onto the brain
• outline the case study of Phineas Gage on localisation of function

  had a rod propelled through his skull

  • became impulsive, rude and alienated himself
  • frontal lobe was responsible for personality and reasoning
• outline the role of the motor cortex

  placed at the back of the frontal lobe

  • governs voluntary movements
  • hemispheres control muscles on opposite side of body

  
• outline the role of the somatosensory area

  front of the parietal lobe

  • detects sensory events
  • hemisphere processes touch, pain, pressure and heat from opposite side of body
  • produces sensation in relevant locations

  
• outline the role of the visual cortex

  found in occipital lobe

  • hemisphere receives input from opposite visual field
  • specialised for colour, shape, movement, pattern and face recognition
  • information is sent to relevant regions

  
• outline the role of the auditory cortex


  found in temporal lobe

  • responsible for sound processing and recognition
  • separate sections for music and sounds
  • sends signals to other brain regions for appropriate response

  
• outline the role of the Broca's area

  Broca - studied patients with posterior left frontal lobe damage

  • involved in cognitive tasks and language production
  • aphasia consists of limited and clumsy speech and writing

  
• outline the role of the Wernicke's area

  Wernicke - studied patients with left temporal lobe damage

  • responsible for language comprehension
  • aphasia consists of limited understanding of language and inability to form coherent speech

  
• one strength of localisation of function

  research support

  • Dejerine et al - loss ability to read from damage between visual cortex and Wernicke's area
  • supports the role of Wernicke's area
• one weakness of localisation of function

  equipotentiality

  • brain is plastic, if one is damaged than another region takes over the function
  • functions aren't specific to brain regions
• second weakness of localisation of function

  individual differences

  • Bavelier - variability in patterns of activation across different individuals when reading
  • activity in temporal, frontal and occipital lobe
  • impacts credibility
• third weakness of localisation of function

  oversimplified

  • Dronkers et al - re-examined Broca's patients
  • other areas contributed to reduced speech abilities
  • Broca's area isn't the only region for speech
• fourth weakness of localisation of function

  deterministic approach

  • only focuses on biological factors in brain functions
  • ignores social or environmental factors
  • reductionist
• define lateralisation

  two halves of the brain are functionally different
• what is the role of the right hemisphere?

  process information from the left half of the body

  • face recognition, drawing ability and spatial tasks
• what is the role of the left hemisphere?

  process information from the right half of the body

  • language
• outline what a split brain patient is

  individuals who had a corpus callosotomy

  • corpus callosum is severed to separate the two hemispheres
  • controls epileptic fits
• outline Sperry's study on split brain patients?

  investigated what functions of the brain are lateralised

  • compared split brain patients to others without hemisphere separation
  • used different activities to see how different sides perform
  • visual tasks - words or pictures in visual field and asked about stimuli
  • tactile tasks - P's hands underneath screen and couldn't see what they were doing
• what were the findings of Sperry's study on lateralisation of function?

  describing visual field

  • left - couldn't describe it
  • right - easily describe pictures shown to them

  recognition by touch

  • left - able to select item but couldn't say anything
  • right - can identify item but not pick it up

  drawing

  • better when drawn by left hand
  • right hemisphere is superior at drawing ability
• one strength of lateralisation of function

  advantegous

  • Rogers - chickens have enhanced in dual task performance
  • animal study so can't be generalised
  • benefits individual but lacks validity
• second strength of lateralisation of function

  research support

  • Szaflarski - language become more lateralised with increasing age
  • can't isolate external factors
  • evidence for change over time but lacks generalisability
• one weakness of lateralisation of function

  language isn't restricted

  • Turk et al - patient suffered damage to left hemisphere
  • had capacity to speak in the right hemisphere
  • brain plasticity and law of equipotentiality
• define plasticity of the brain

  the brain's ability to adapt as a result of experience
• define functional recovery of the brain

  the brain's ability to transfer functions performed by damaged area to other undamaged ones
• outline plasticity of the brain

  • brain can change throughout life
  • at infancy, brain has rapid increase of synaptic connections
  • existing neural connections change or formed due to learning and experience
• what is the structural process of plasticity?

  1. neurogenesis - growing new neurons or axons
  2. synaptogenesis - making new connections between neurons
  3. synaptic pruning - destroy unused connections and strengthen most used connections
• what did Boyke et al find out about plasticity?

  new skills

  • 60 year old individuals were taught how to juggle
  • increased grey matter in visual cortex
  • when practicing stopped, changes were reversed
• what did Kuhn et al find out about plasticity?

  playing video games

  • group was trained for 2 months for 30 minutes per day
  • increase in grey matter across the brain
  • resulted in new synaptic connections
  • spatial navigation, strategic planning, working memory and motor performance
• what did Davidson et al find out about plasticity?

  meditation

  • 8 practitioners with 10 volounteers
  • electrodes picked up slight activation of gamma waves
  • changes working of brain in short term
• what did Kempermann et al find out about plasticity?

  animal research

  • one group of rats had complex house and the other had lab cages
  • rats with complex environment had larger hippocampi
  • importance of memory and spatial navigation skills
• what is the 3 step process of functional recovery?

  1. neural unmasking
  2. stem cells
  3. neural reorganisation
• outline neural unmasking as part of functional recovery

  • inactive connections called dormant synapses
  • when region is damaged, signals can be rerouted through dormant synapses
  • neural communication can continue as abilities are recovered
• outline stem cells as part of functional recovery

  • implant them to directly replace damaged or missing cell
  • implant next to damaged area so growth factors can repair them
  • creates pathway to reroute communication to take over function
• outline neural reorganisation as part of functional recovery

  • brain can get other locations to perform damaged function
  • recruit homologous regions to take on lost function
  • process is a laterality shift
• one strength of plasticity and functional recovery

  practical application

  • neurorehabilitaition
  • physical therapy and electrical stimulation of brain
  • brain can "fix itself" but needs further intervention
• one weakness of plasticity and functional recovery

  negative plasticity

  • 60 - 80% of amputees have phantom limb syndrome
  • unpleasant and painful sensations
  • maladaptive behavioural consequences
• second strength of plasticity and functional recovery

  age and plasticity

  • greater ability to reorganise in childhood as constantly adapting
  • Bezzola - 40 hours of gold changed neural representation of participants aged 40 to 60
  • neural plasticity continues throughout lifespan