A03 Localisation Of Function In The Brain

• Brain scan evidence of localisation

  There is a wealth of evidence providing support for the idea that many neurological functions are localised, particularly in relation to language and memory
• Petersen et al and Tulving et al (Brain scan evidence of localisation)


  Used brain scans to demonstrate how Wernicke's area was active during a listening task and Brocas area was active during a reading test, suggesting that these areas of the brain have different functions. Also, Tulving et al revealed that semantic and episodic memories reside in different parts of the pre-frontal cortex
• Scientific evidence (Brain scan evidence of localisation)

  There now exists a number of highly sophisticated and objective methods for measuring activity in the brain which provide sound scientific evidence of localisation of brain function
• Neurosurgical evidence


  Freeman developed the lobotomy which was a brutal and inprecise as it typically involved severing connections in the frontal love in an attempt to control aggressive behaviour . Neurosurgery is still used, but sparingly, in extensive cases of OCD and depression.
• Dougherty et al (Neurosurgical evidence)


  Reported on 44 patients with OCD who've undergone a cingulotomy (lesioning of the cingulate gyrus). There was a post surgery follow up after 32 weeks and a third met the criteria for successful response while 14% had a partial response. This suggests symptoms / behaviours associated with mental disorders are localised.
• Case study evidence


  Phineas Gage was working in the railword when an explosion occured causing a metre length pole to go through his left cheek passing behind his left eye. Gage survived but his left frontal lobe was damgaged changing his personality. He turned from someone calm to being rude and no longer 'Gage'. He's a 'landmark in science'.
• Lashley's research


  Argued that higher cognitive functions such as processes involved in learning, are not localised but distributed in a more holistic way. Lashley removed areas of the brain cortex (10-15%) in rats that were learning a maze.
• Findings of Lashley's research


  No area was proven to be more important than any other area in terms of ability to get out the maze. Process required every part of the cortex which suggest learning is too complex to be localised and requires involvement of the whole brain.
• Plasticity


  Plasticity (cortical remapping) is a compelling argument against localisation. When damaged, the brain and particular functions have been compromised/lost yet the brain appears able to reorganise itself in an attempt to recover the lost function.
• Law of equipotentiality (Plasticity)

  Lashley calls the process of plasticity the 'law of equipotentiality' where the surviving brain circuits chip in so the same neruological activity can be achieved as before the damage. For example, several documented cases of stroke vcictims being able to recover those activities that were seemingly lost.