Localisation of function in the brain

• Localisation


  our physical and psychological abilities all come from specific brain area.

  this was found from lesion studies, port-mortem, case studies and eventually could be looked at using brain scanning technology when it was developed.
• Holistic Theory


  assumes that the whole brain is involved in all brain processes.
• Hemisphere of the Brain

  - left hemisphere is dominant in language processing.

  - right hemisphere is dominant in spatial processing.

  contralateral - left hemisphere is responsible for right side of body, right hemisphere is responsible for left side of body.

  outer layer - cerebral cortex - consists of grey matter and it about 3mm thick.
• Frontal Lobe


  at the back of this lobe is the motor area.

  this is where the brain processes body movement.
• Parietal Lobe


  at the front of this lobe is the somatosensory area.

  this is where the brain processes touch.
• Temporal Lobe


  in this lobe is the auditory area.

  this is where the brain processes what you hear.
• Occipital Lobe


  this contains the visual area.

  this is where the brain processes sight.
• Language Areas in the Brain

  language is restricted to the left side of the brain.

  Broca - identified a small area in the left frontal lobe which is responsible for speech production.

  - damage to this area causes Broca's aphasia which is characterised by slow speech that lack fluency (non-fluent aphasia).

  Wernicke - identified a different area of the brain in the left temporal lobe which is believed was responsible for language comprehension.

  - damage to this area causes Wernicke's aphasia which is characterised by nonsense word (fluent aphasia)
• Strength - Case Study evidence

  Phineas Gage - involved in an accident in which a metre long tamping iron hurled into Gage's cheek, passing at the back of his left eye and through the top of his skull.

  - before accident: calm and reserved.

  - after accident: quick-tempered and aggressive.

  - suggests that the frontal lobe may have something to do with mood regulation.
• Strength - Neurological Evidence

  - neurosurgery - controversial matter.

  - Dougherty et al -> reported on 44 OCD patients who had undergone a cingulotomy - which is lesioning in the lingulate gyrus.

  he found that 1/3 of patients had a successful response to the surgery and there was a 14% partial success rate.

  - suggests that symptoms and behaviours related to certain disorders are localised in the brain.
• Strength - Brain Scanning Evidence

  - Petersen et al - found that Wernicke's area was active during a listening task and Broca's area was active during a speaking task. suggests that 2 areas do have different functions.

  - Tulving et al - when ppts recalled semantic and episodic memories, different regions of their prefrontal cortex was activated.

  Scientific Methods - EEG, fMRI, - all objective measures.
• Weakness - Not all Localised

  Lashley suggests that some higher cognitive functions aren't localised but are instead distributed in a more holistic way.

  - studied this by removing 10% and 50% of cortex in brains of rate who were learning to make their way round a maze.

  - learning appeared to involve every area of the cortex rather than a specific lobe or area.
• Weakness - Plasticity


  when damage to the brain occurs, the brain is able to re-map itself and recover lost functions.

  Lashley - Law of Equipotentiality - where the surviving brain areas 'chip in' so that the brain can still perform the apparently lost function.

  - e.g. there have been many stroke victims who have been able to recover lost or compromised abilities.