LOCALISATION OF FUNCTION

• Localisation of function - the theory that different areas of the brain are responsible for specific behaviours , processes or activities
• Language is restricted to the left side of the brain in most people.
• What are the evaluation points for localisation of function?

  Strength - brain areas have been linked to mental disorders

  ( Dougherty )

  Strength - evidence from brain scans and memory ( Petersen et al , Buckner and Peterson )

  Counter arguement - rat study ( Lashley )

  Weakness - location of language
• EVALUATION - BRAIN AREAS HAVE BEEN LINKED TO MENTAL DISORDERS

  A strength of localisation of function is that damage to areas of the brain have been linked to mental disorders. Dougherty et al. reported on 44 people with OCD who had undergone a cingulotomy. Cingulotomy is a procedure that isolates a region called the cingulate gyrus. After 32 weeks, 30% had met the criteria for successful response to the surgery and 14% for partial response. The success of these procedures suggests that behaviours associated with mental disorders may be localised.
• EVALUATION - EVIDENCE FROM BRAIN SCANS AND MEMORY ( part 1 )

  A strength of localisation of function is that there is evidence from brain scans that supports the idea that many everyday brain functions are localised. Petersen et al. used brain scans to demonstrate how Wernicke's area was active during a listening task and Broca's area was active during a reading task.
• EVALUATION - EVIDENCE FROM BRAIN SCANS AND MEMORY ( part 2 )

  Additionally, a study of long-term memory by Buckner and Peterson revealed that semantic and episodic memories are located in different parts of the prefrontal cortex. These studies confirm localised areas for everyday behaviours. Therefore objective methods for measuring brain activity have provided scientific evidence that many brain functions are localised.
• EVALUATION - COUNTER ARGUMENT

  A challenge to localisation of function comes from Lashley’s study. Lashley removed areas of the cortex in rats that were learning the route through a maze. No area was proven to be more important than any other area in terms of the rats' ability to learn the route. The process of learning seemed to require every part of the cortex rather than being confined to a particular area. This suggests that higher cognitive processes , such as learning , are not localised but distributed in a more holistic way in the brain.
• EVALUATION - LOCATION OF LANGUAGE ( part 1 )

  A limitation of localisation of function is that language may not be localised just to Broca's and Wernicke's areas. Advances in brain imaging techniques mean that neural processes in the brain can be studied with more clarity. It seems that language function is distributed far more holistically in the brain than was first thought. Language streams have been identified across the cortex , including brain regions in the right hemisphere , as well as subcortical regions such as the thalamus.
• EVALUATION - LOCATION OF LANGUAGE ( part 2 )

  This suggests that language may be organised holistically in the brain, which contradicts localisation theory.