localisation of function in the brain

• The cerebral cortex is divided into four lobes, including the frontal lobe.
• localisation of function is the theory that different areas of the brain are responsible for different functions
• the motor area controls voluntary movement
• the somatosensory area receives sensations from the body
• contralateral means each hemisphere of the brain controls the opposite side of the body
• the motor area is found in the frontal lobe
• the somatosensory area is found in the parietal lobe
• the auditory area is found in the temporal lobe and is responsible for processing auditory information
• the visual area is found in the occipital lobe of the brain and is responsible for processing visual information
• broca’s area is located in the left frontal lobe and is responsible for speech production
• broca’s aphasia is a language disorder that affects the ability to speak and understand language and is characterised by slow language production and difficulty finding the right words
• wernicke’s area is responsible for language comprehension and is found in the left temporal lobe
• wernicke's aphasia is a language disorder that affects the ability to comprehend spoken or written language, often resulting in fluent but nonsensical speech.
• hemispheric lateralisation is the idea that the left and right hemispheres of the brain are specialised for different tasks
• broca’s area and wenicke’s area are only found in the left hemisphere of the brain
• broca’s area was discovered after case study and post mortem examinations of tan, his brain showed damage to the left frontal lobe
• damage to both broca’s and wernicke’s area can lead to global aphasia, which is the inability to produce or understand speech
• AO3 - clinical case study research - broca and wernicke’s area - suggests functions are localised to these areas

  HOWEVER

  case studies are unscientific - especially in brain research - MRI of tan’s brain presented damage in multiple regions, meaning that other areas could be responsible for tan’s speech problems
• AO3 - evidence from brain scans - petersen et al, demonstrated that wernicke’s area was active during a listening task and broca’s area was active during reading task

  buckner and petersen, demonstrated how semantic and episodic memories reside in different parts of the prefrontal cortex

  indicates that objective methods provide evidence for localisation of the brain

  HOWEVER - lashley
• AO3 - lashley (1925) - 50 rats run a maze before and after areas of the cortex is removed (10% - 50%)

  ability to successfully run route was affected by how much brain cortex was destroyed not which area.

  suggests higher cognitive processes, such as learning, are not localised but distributed throughout the brain in a more holistic way
• the principle of mass action is the idea that the more the brain is destroyed, the worse functioning becomes
• phineas gage - damaged his left frontal lobe - his personality changed due to this damage
• lashley proposed the equipotentiality theory, which suggests that the basic motor and sensory functions are localised, but that higher mental functions are not.
• AO3 -theories of localisation are biologically reductionist in nature and try to reduce very complex human behaviours and cognitive processes to one specific brain region.
• AO3 - ignores individual differences

  herasty (1997) found that women have proportionally larger Broca’s and Wernicke’s areas than men, which can perhaps explain the greater ease of language use amongst women.

  beta bias -

  the differences between men and woman are ignored, and variations in the pattern of activation and the size of areas observed during various language activities are not considered.