Localisation of function in the brain

• Localisation

  The theory that specific areas of the brain are associated with particular physical and psychological functions
• Hemispheres

  • The brain is divided into two hemispheres: left and right
  • Lateralisation: some physical and psychological functions are controlled by particular hemisphere
  • Each hemisphere is responsible for specific functions. Generally, the left side of the body is controlled by the right hemisphere; The right side of the body is control by the left hemisphere
• Motor Area

  • at the back of the frontal lobe(in both hemispheres) is the motor area
  • This controls voluntary movements in the opposite side of the body
  • Damage to this area the brain may result in a loss of control over fine movements
• Somatosensory Area

  • at the front of both priority lobes is the somatosensory area
  • This area is where sensory information from skin is represented
  • Sensitive areas of our skin occupying more of the somatosensory area
• Visual area

  • In the occipital lobe at the back of the brain is a visual area (or visual cortex)
  • Each eye sent information from the right visual field to the left visual cortex and vice versa
  • This means that damage to the left hemisphere can produce blindness in part of the right visual field of both eyes
• Auditory Area

  • The temporal lobes, house the auditory area which analyses speech based information
  • Damage may produce partial hearing loss
  • Damage to a specific area of the temporal lobe- Wenicke’s area - may affect ability to comprehend language
• Language area of the brain: Broca’s Area speech production

  • Languages restricted to the left side of the brain in most people
  • In 1880, Broca identified a small area in the left frontal lobe responsible for speech production
  • damage to Broca’s area causes Broca’s aphasia which is characterised by slow and laborious speech
  • broca’s patient may have difficulty finding words and naming certain objects
• Language areas of the brain: Wernicke’s Area understanding language

  • Wernicke was describing patients who had no problem producing language but severe difficulties understanding it
  • Their speed of speech was fluent but meaningless
  • Wernicke identified a region in the left temporal lobe as being responsible for language comprehension
  • This would result in Wenicke’s aphasia when damaged ( producing nonsense words in speech)
• Evaluation

  • One strength is that the is brain scan evidence to support it

  • Peterson et al. (1988) found activity in Wernicke’s and Broca’s areas during listening and reading tasks.

  • Tulving's study of long-term memory revealed semantic and episodic memories in different frontal cortex parts.

  • These methods provide scientific evidence of brain localisation of function.
• Evaluation

  • strength : support from neurological evidence
  • Surgically removing/destroying areas of the brain to control aspects of our behaviour was developed in the 1950s
  • Dougherty reported on 44 OCD patients who had part of their brain tissue removed to treat the OCD and found that one third showed a successful response
  • the success of such procedures strongly suggest that symptoms and behaviours are associated with serious mental disorders are localised. This is because one of those specific areas of the brain are removed in some cases, disorder disappears.
• • strength: is support from case studies
  • ,Phineas Gage received serious brain damage in an accident. A pole went through part of his frontal lobe. He survived but the damage to his brain affected his personality – he went from someone who was calm and reserved to someone quick-tempered and rude
  • The change in Gage’s personality following the accident suggests the frontal lobe may be responsible for regulating mood. 
  • supports localisation theory as it suggests that one specific area of the brain (frontal lobe) is responsible for a specific psychological function (mood).
• • limitation : Neuroplasticity is a challenge to localisation theory
  • When one part of the brain has become damaged and a function has been lost the rest of the brain is able to re-organise itself to recover the function.
  • Stroke victims sometimes regain cognitive abilities after damage to specific brain areas, allowing other areas to 'chip in' and achieve the same function.
  • This is a limitation of localisation theory because it suggests that all parts of the brain work together to enable specific functions, rather than one single area solely being responsible