Localisation of function in the brain

• Localization of function


  The idea that particular behavioral functions like moving your arm or producing speech are localized to particular regions of the brain, in contrast to a holistic understanding of the brain where functions are spread out across large areas or the entire brain
• Regions of the brain demonstrating localization of function

  • Visual cortex
  • Motor and somatosensory cortices
  • Auditory cortex
  • Broca's area
  • Wernicke's area
• Broca's area and Wernicke's area are generally in the left hemisphere, demonstrating lateralization of function
• Contralateral


  The right hemisphere moves and senses the left side of the body, and the left hemisphere moves and senses the right side of the body
• Cortex


  The thin outside layer of the brain, where much of the brain's processing takes place
• Visual cortex


  • Located in the occipital lobe at the back of the brain
  • Damage can cause partial or complete blindness (cortical blindness)
  • Left and right visual cortices are contralateral
• Motor cortex


  • Located in the frontal lobe
  • Plans and carries out voluntary motor movements on the opposite side of the body
  • Damage can lead to loss of fine muscle function or paralysis on the opposite side
• Somatosensory cortex


  • Located in the parietal lobe
  • Detects sensations from the opposite side of the body
  • Damage can lead to loss of sensation, neglect syndrome, or agnosia
• Auditory cortex


  • Located at the top of the temporal lobe
  • Receives auditory or sound sensations from the ears
• Broca's area


  • Located in the left frontal lobe
  • Responsible for speech production
  • Damage leads to Broca's aphasia (difficulty producing fluent speech)
• Wernicke's area


  • Located in the left temporal lobe
  • Responsible for speech comprehension
  • Damage leads to Wernicke's aphasia (difficulty understanding written or spoken language)
• Damage to both Broca's and Wernicke's areas can lead to global aphasia (inability to produce or understand speech)
• The debate about holistic or localized nature of brain functions has been long-lasting
• The motor and somatosensory cortices map out the body, with different areas taking up different amounts of space depending on the amount of sensory and motor information processing needed
• This mapping is represented in the homunculus, a 3D model demonstrating how the brain perceives the body