Localisation of the brain

• What’s the localisation of function mean?

  refers to the belief that different parts of the brain are involved in different tasks and are associated to different behaviours
• specific functions such as language, hearing, memory etc. have specific locations within the brain
• if a certain area of the brain becomes damaged through illness or injury, the function associated with that area will also be affected
• The brain has two symmetrical hemispheres
• Psychological and physical functions are controlled/dominant by a particular hemisphere - lateralisation
• Left side of the body - controlled by the right hemisphere and vice versa
• The outer layer of both hemispheres is called the cerebral cortex
• Our cerebral cortex separates us from animals because ours is more developed
• Both hemispheres are sub- divided into four lobes (frontal, temporal, parietal, occipital)

  Each lobe is associated with different functions
• Where is the motor area located ?


  The motor area is located at the back of the frontal lobe in both hemispheres, along a bumpy region known as the precentral gyrus
• What is the motor area responsible for?


  This controls voluntary movement in the opposite side of the body (the brain is wired to work in opposites i.e. contralateral)
• where is the somatosensory area located ?


  At the front of both parietal lobes, along a region known as the postcentral gyrus is the somatosensory area
• What is the somatosensory area responsible for ?

  The somatosensory area is where sensory information from the skin (e.g. related to heat, touch, pressure etc) is represented

  As with the motor cortex, both hemispheres have a somatosensory cortex, with the cortex on one side of the brain receiving sensory information from the opposite side of the body – Contralateral
• Where is the visual centres located ?

  The primary visual centre in the brain is located in the visual cortex, in the occipital lobe at the back of the brain
• What does each eye do?

  Each eye sends information from the right visual field to the left visual cortex and from the left visual field to the right visual cortex
• if there is damage in the left visual

  cortex, where could blindness be produced?

  The right visual field of both eyes
• Where’s the auditory centres ?

  • Most of this area lies within the temporal lobes on both sides of the brain, where we find the auditory cortex.
• • The auditory centre in the brain is concerned with hearing
  • The auditory cortex analyses speech-based information
• What could damage to the auditory cortex result in ?

  Partial hearing loss, the more extensive the damage, the more extensive the loss
• Where is language found ?

  language is restricted to the left hemisphere for most people
• In the 1880s, Paul Broca, a French neurosurgeon, identified a small area in the left frontal lobe responsible for speech production

  Case study – Tan: so called because that was the only word that he could say

  Damage to Broca’s area causes Broca’s aphasia – characterised by speech that is slow, laborious and lacking in fluency
• Around the same time as Broca, Karl Wernicke was describing patients who has no problem producing language but severe difficulties understanding it - speech produced was fluent, but meaningless
• Wernicke’s area is in the posterior of the left temporal lobe and is responsible for language processing
• When Wernicke’s area is damaged, this can lead to Wernicke’s aphasia –what might this look like in a

  patient?

  Nonsense speech, even nonsense words (neologisms)
• Whats evaluations for the localisation of the brain?

  :) One strength of localisation theory is support from neurosurgery - ( Dougherty et al ) - OCD

  :) its supported by case studies with brain damaged patients such as Gage - personality change

  :( The claim that functions are localised to certain areas of the brain has been criticised ( lashley )