localisation of function

• curious case of phineas gage

  • 1848 explosion hurled meter length pole through gage's left cheek exiting his skull from the top of his head taking a portion with his brain with it (most of left frontal lobe). gage survived but damage to brain left mark on personality - from calm to quick tempered. gage seen as landmark case - suggests frontal lobe may be responsible for regulating mood
  • before scientists supported holistic theory that all parts are involved in thought and action - scientists now argue we have localisation of function in brain after gage
• cerebrum


  higher functions (emotion, thinking)
• brainstem


  basic life functions (breathing, heart)
• cerebellum


  basic motor control, balance and some simple learning
• localisation of function


  during the 19th century it was discovered that certain areas of the brain held specific functions
• localisation


  specific areas of the brain are associated with specific physical and psychological processes
• hemisphere

  • left and right sides of brain are similar
  • one difference is the presence of the language areas which are only found on the left hand side
• Broca


  responsible for converting thought into speech
• Wernicke


  plays a role in understanding people's speech and for producing speech which makes sense
• somatosensory cortex

  • found in both hemispheres
  • produces sensations of touch, pressure, pain, temperature
  • located in parietal lobe of the brain along region known as postcentral gyrus
  • postcentral gyrus is the area of cortex dedicated to processing sensory information related to touch
  • detects sensory events arising from different regions of the body
• visual cortex

  • visual centre of the brain
  • visual processes start in the retina - light hits receptors
  • found in occipital lobe of brain
  • nerve impulses travel from optic nerve from the retina to the brain
  • some impulses travel to an area of brain involved in coordination of circadian rhythms but most terminate in thalamus
  • found in both hemispheres
  • different areas responsible for different types of visual information
• auditory cortex

  • auditory centre in brain is concerned with hearing
  • auditory pathways begin in the cochlea in the inner ear
• wernicke's area

  • contains sensory region
  • located in the posterior portion of the left temporal lobe
  • close to regions of the brain responsible for auditory and visual input (where spoken language is proceeded)
• motor cortex

  • both hemispheres of the brain have a motor cortex - each side controls opposite sides of the body
  • responsible for voluntary motor movement
  • located in the frontal lobe
• Broca's area

  • posterior portion of frontal lobe of the left hemisphere area is believed to be critical for speech production
  • Paul Broca - french neurosurgeon
• A03 some challenges to localisation an influential conflicting view is the equipotentiality theory (Lashley)

  • Lashley believed that basic motor and sensory functions were localised but the higher mental functions were not
  • He stated that intact areas of the cortex could take over responsibility for specific cognitive functions following injury to the area normally responsible for the function - impact of damage to the brain would be determined by the extent rather than the location of the damage
• A03 language production may not be confined to Broca's area alone

  • Donkers re-examined the preserved brains of two of Broca's patients. Louis Leborgne and Lazare Lelong. They used high resolution MRI imaging to identify the extent of any lesions in more detail
  • MRI findings showed that other areas could have contributed to the patients reduced speech abilities. Although lesions in Broca's area alone can cause temporary speech disruption they dont usually result in severe language disruption
  • localisation is limited in explaining language and cognition
• A03 Aphasia studies support existence of distinct language centers in the brain

  • Brain scans have shown that damage to Broca's and Wernicke's areas have resulted in different types of aphasia
  • Expressive aphasia is an impaired ability to produce language. Receptive aphasia is an impaired ability to extract meaning from spoken or written words
  • this demonstrates the important and distinct roles of these brain regions in different aspects of language