Brain Localisation

• Localisation of function refers to the theory that specific functions (such as language, memory, hearing etc) have specific locations within the brain.
• Broca's Area:

  • 51 year old man transferred to Paul Broca's surgical ward in France.
  • Patient had epilepsy but was near death due to an uncontrolled infection & had extreme difficulty speaking voluntarily.
  • Patient died a few days later, and it was found from an autopsy that there was an especially distinct lesion in his left frontal lobe.
  • Supported hypothesis that language was localised to the frontal lobes, & can be interpreted that patient's brain damage was the root cause of his speech deficit.
• Wernicke's Area:

  • Carl Wernicke discovered that patients with lesions to Wernicke's area were still able to speak, but were unable to comprehend language.
  • People with damage to Wernicke's area struggle to comprehend language, often producing sentences that are fluent, but meaningless- named Wernicke's aphasia.
• Brain Localisation Strength:

  • There's support for language centres from brain scan studies.
  • Peterson et al asked PPs to complete a reading & listening task during a brain scan.
  • Showed Broca's Area to be active during reading & Wernicke's Area to be active for listening.
  • Shows reliability of the theory- scientific evidence.
• Brain Localisation Weakness:

  • Communication of brain areas may be a more important factor than localisation.
  • Complex functions require several interconnecting brain areas, eg reading requires communication between the Visual centres & Wernicke's area.
  • Indicates that purely understanding localised areas is insufficient; it is the interconnectedness of these areas that allows the brain to function.
• Brain Localisation Strength:

  • Support from case studies such as Phineas Gage.
  • Following an accident where a metal pole destroyed part of his frontal lobe, Gage had personality changes and was more impulsive & aggressive.
  • Supports that personality & ability to rationalise & control impulses is localised to the frontal cortex.
• Brain Localisation Weakness:

  • There are individual differences in language centres.
  • Bavelier et al (1997) asked pps to read silently and found large variability in activation of different brain centres across individuals, eg right temporal & left frontal temporal & occipital lobes.
  • This leads to a lack of coherence in the theory of specific localisation of language centres.