A03

• Point: A strength of the localisation theory is that there is supporting evidence from mental disorders.

  Evidence: For example, a cingulotomy is a type of neurosurgery which isolates a specific part of the brain (cingulate gyrus) which has been implicated in OCD.

  Explain: Dougherty (2002) has shown that of 44 people with OCD who had undergone this procedure, about 30% had met the criteria for successful response at a 32 week follow-up.

  Link: Therefore, this suggests certain behaviours (e.g. OCD) may be localised in the brain based on the success of some of these procedures.
• Point: Further supporting evidence for the localisation theory comes from brain scans.

  Evidence: For example, Peterson (1988) used brain scans which revealed that Wernicke’s area was active during listening tasks while Broca’s area was active during reading tasks.

  Explain: Similarly, other studies have shown that semantic memory and episodic memories are linked to different parts of the prefrontal cortex.

  Link: Therefore, such studies confirm that many everyday brain functions are indeed localised, using objective and scientific methods.
• Point: However, a limitation to the localisation theory is evidence that suggests brain functions may not be localised.

  Evidence: For example, Lashley (1950) removed different areas of cortex (between 10-50%) in rats that were learning the route of a maze.

  Explain: The results showed that no rat was more disadvantaged in terms of their ability to learn the route.

  Link: Therefore, this suggests that higher cognitive processes, such as learning, are not confined to one specific brain area but spread in a more holistic way in the brain.
• Point: Another limitation is evidence which suggests that the language centres may not be localised to just Broca’s and Wernicke’s areas.

  Evidence: For example, advanced brain scanning techniques, such as fMRI, are able to show that language function is distributed more holistically than originally thought.

  Explain: This means that language streams have been identified throughout the cortex, as well as in the right hemisphere, and even in subcortical areas.

  Link: Therefore, this contradicts localisation theory as it shows language is organised more holistically in the brain.