Localisation of function in the brain

• Localisation of Function

  • Specific areas of the brain are associated with particular functions.
  • If a certain area becomes damaged through illness or injury, the function associated with that area will also be affected.

  Supported by Broca and Wernicke.
• Holistic Theory


  All parts of the brain are involved in the processing of thought and action.

  Generally supported up to the 19th Century.
• Hemispheres

  Two symmetrical halves of the brain.
• Right Hemisphere


  Activity on the left-side of the body is controlled by the...
• Left Hemisphere


  Activity on the right-side of the body is controlled by the...
• The Cerebral Cortex


  The outer layer of both hemispheres - Covers the inner parts of the brain.

  3mm thick and appears grey.

  More developed in humans than in other animals
• Frontal Lobe

  Contains the motor cortex - controls voluntary movement in the opposite side of the body.

  Damage to this area may inhibit movement and loss of control over fine movements
• Parietal Lobe

  Contains the somatosensory cortex - directs sensory events arising from different regions of the body

  Damage to this area results in failure to feel heat, pressure, or taste as the message will not be delivered.
• Occipital Lobe

  Contains the visual cortex - each eye sends information from the right visual field to the left visual cortex and from the left visual field to the right visual cortex

  Damage to this area results in visual impairment or distorted perception of sights
• Temporal Lobe

  Contains the auditory cortex - analyses speech-based information

  Damage to this area results in delayed communication and inability to form tangible sentences. Also a possible reduction in hearing ability.
• Left Frontal Lobe

  Location of Broca's area
• Left Temporal Lobe

  Location of Wernicke's area
• Broca's Area

  - Responsible for speech production

  Damage to this area results in slow speech, laborious and lack of fluency ( Broca’s aphasia)
• Wernicke's Area

  - Responsible for language comprehension

  
  

  Damage to this area results in production of nonsense words (neologisms) and unrelated sentences ( Wernicke’s aphasia)
• Broca's Aphasia

  Speaking in short phrases that make sense but require great effort.

  
  

  E.g. They will say "walk dog" not "I will take the dog for a walk"
• Wernicke's Aphasia

  • Speaking in long sentences that have no meaning with the addition of made-up words.
  • Have great difficulty understanding speech and are unaware of their mistakes.
• Support for Localisation of Function - 1

  Phineas Gage - survived after having his left frontal lobe damaged in a railroad accident.

  However, there were massive changes to his personality - this may further support localisation as the left frontal lobe may be responsible for mood and personality.
• Support for Localisation of Function - 2

  Peterson et al (1988) - brain scans demonstrated: Wernicke's area = active during listening task

  Broca's area = active during reading task
• Support for Localisation of Function - 3

  Dougherty et al (2002) - Neurosurgery on OCD patients - 44 OCD patients undergone cingulotomy (injuring the cingulate gyrus) - 1/3 fully recovered

  However, 2/3 did not, suggesting that localisation is not as comprehensive and applicable to all.
• Support for Holistic Theory - 1

  Lashley (1950) - removed areas of the cortex in rats trying to learn a maze.

  Found that the process required every part of cortex rather than being confined to one place.

  However, rats are not humans
• Support for Holistic Theory - 2

  Lashley - 'Law of Equipotentiality"

  - Brain becomes damaged by illness or injury

  - Where the function is lost or compromised, the rest of the brain attempts to reorganise itself in an attempt to recover the lost function
• Diagram of the brain