localisation and hemispheric lateralisation

• the brain is contralateral
• the left hemisphere deals with language tasks
• the right hemisphere deals with motor tasks
• researchers like broca and wernicke have argued for localisation of function - different parts of the brain are responsible for different tasks
• the cerebrum is split into two symmetrical halves, the functions are conducted by a particular hemisphere - this is lateralisation
• the left hemisphere controls the right side of the body and the right hemisphere controls the left side of the body
• the intake of visual information and processing is more complex

  vision is contralateral and ipsilateral

  each eye receives light from the left visual field and the right visual field

  the lvf of both eyes is connected to the right hemisphere and the rvf of both eyes is connected to the left hemisphere
• visual cortex

  located in the occipital lobe

  
• visual cortex

  visual processing is the primary function

  located in the occipital lobe

  present in both hemispheres

  visual information present in left field of vision is processed in the right etc
• auditory cortex

  located in the temporal lobe

  
• auditory cortex

  responsible for hearing

  located in temporal lobe

  present in both hemispheres, auditory information present in left ear will be processed in right

  damage may therefore produce partial hearing loss
• somatosensory cortex

  located in parietal lobe

  
• somatosensory cortex

  detects sensory information from the skin, eg touch, heat, pressure

  located in parietal lobe where it meets the frontal lobe, seperated by central sulcus

  present in BOTH hemispheres

  sensory info detected in right side will be dealt with by the left hemisphere

  highly localised
• motor cortex

  located in frontal lobe

  
• motor cortex

  voluntary movement and fine motor skills

  located in frontal lobe

  present in both hemispheres

  movement in right side controlled by left hemisphere

  highly localised
• broca’s area

  frontal lobe in the left hemisphere only

  
• broca’s area

  language and specifically speech production

  in the frontal lobe with left hemisphere only

  broca’s aphasia
• broca’s aphasia

  case of Tan- can only understand spoken language but unable to speak/express thoughts in writing

  comprehension is preserved
• wernicke’s area

  temporal lobe and left hemisphere only

  
• wernicke’s area

  responsible for language and language comprehension

  located in temporal lobe in left hemisphere only

  wernickes aphasia
• wernicke’s aphasia

  lesions in posterior portion of left temporal lobe could speak but couldn’t understand language
• hemispheric lateralisation

  the dominance of one hemisphere of the brain for particular function
• split brain

  when the corpus callosum has been severed preventing communication between the left and right hemispheres
• how do we test split brain?

  isolate visual fields. show two images to each eye then ask participants to respond verbally with what the see
• split brain results


  objects in LVF could only be identified by drawing/pointing

  objects in RVF could be verbally described
• split brain results - why?

  LVF processed by RH

  RVF processed by LH
• split brain research

  :-) increase understanding of brain function, gazzaniga, increased neural capacity

  :-) standardised procedures

  :-( split brain patients are rare, basically case studies

  ++ :-( severe epileptics are the main sample
• evaluating localisation of function/lat

  :-) provide support for the idea many everyday brain functions are localised, peterson et al, wernickes area was active during reading. empirical evidence strengthens